May | 2020 | Paynter's Palace

Posted 26 May 2020,

This post describes a small Teensy program developed to drive a NEMA 17 stepper motor to perform angular scans that can be used in conjunction with another program to obtain angle-synchronized performance data.

In a post several years ago I mentioned that I had developed a small Teensy program to drive a NEMA 17 stepper motor to perform angular scans to test Wall-E2’s IR Homing detection performance. Unfortunately, I didn’t do a very good job of documenting the setup, so when I wanted to use the same capability for my new VLX53L0X ‘Time-of-Flight’ sensor project, I was unable to easily put the pieces back together again. So, I decided to create a post dedicated to the software/hardware setup and usage, so the next time I need this capability it won’t be so hard to access.

The original rotary scanner program worked OK, but there was no way to synchronize the rotary table with the measurement program. So I decided this time around I was going to add some features to make it more usable:

It should allow the measurement program to trigger the start of the scan, and trigger each subsequent rotation to the next position, in a measure-move-measure… sequence.
It should provide notification when each scan position has been reached, and when the entire scan is complete
It should allow for repeated scans without restarting the program
It should be capable of reporting each position step number and calculated angle relative to the set zero position to the measurement program via I2C.

Here’s the wiring diagram:

Wiring diagram for Rotary Table program

And the software

/*
    Name:       Teensy_NEMA17_L298N_RotaryTable.ino
    Created:	5/27/2020 11:00:40 AM
    Author:     FRANKNEWXPS15\Frank
*/

/*
Teensy NEMA 17 L298N Rotary Table Program

This program controls a NEMA 17 stepper motor using an L298N motor driver. It
Takes user input to define the boresight (zero) position and the start and stop angles
in degrees relative to the zero position.  Then it moves to the start position and waits 
for a HIGH level on SCAN_START_PIN.  After this signal is received, the motor is 
stepped through to the stop position. At the stop position, the SCAN_COMPLETE_PIN is 
driven HIGH.

The Stepper motor is connected to an L298N motor driver with one coil on Out1/2, and the
other coil on Out3/4.  It may turn out that one coil's leads have to be reversed to match
the motor rotation direction with the program direction.  

The Teensy 3.2 is connect to In1/2/3/4 via pins 8,9,10,11 although this can be changed in the
constructor below.

The NEMA 17 motor is assumed to execute 200 steps/revolution.  Change the StepsPerRevolution
constant for other values.

05/27/20:  Performs an angular scan over user-supplied range of angles. By default a complete scan
from start position to stop position is performed, followed by a return to the start position
However, if the STEP_ENABLE_PIN (held HIGH by default) is pulled LOW, the program will wait 
until it goes HIGH before performing the next step.  In this case, a scan iteration would go
as follows

	Step 1 - Scan paramaters entered, motor moves to start position, waits for LOW on SCAN_START_PIN
	Step 2 - Measurement program pulls SCAN_START_PIN LOW for 1 sec, then back HIGH 
	Step 3 - Measurement program takes a measurement & retrieves step# & angle value via I2C request
	Step 4 - Measurement program pulls SCAN_STEP_ENABLE_PIN LOW
	Step 5 - Motor moves to first/next step, and outputs HIGH on SCAN_STEP_COMPLETE_PIN
	Step 6 - Measurement program waits for HIGH on SCAN_STEP_COMPLETE_PIN
	Step 7 - Measurement program takes a measurement & retrieves step# & angle value via I2C request
	Step 8 - Repeat Steps 4-7 until scan complete
	Step 9 - SCAN_COMPLETE_PIN goes HIGH
*/

//O5/30/20 Added I2C connection to pass step# & relative angle values to measurement program

#include <Stepper.h>
#include <Wire.h>
#include "I2C_Anything.h"


// change this to fit the number of steps per revolution for your motor
const int stepsPerRevolution = 200;

// initialize the stepper library on pins 8 through 11:
Stepper myStepper(stepsPerRevolution, 8, 9, 10, 11);

//08/26/17 added for scan support
const int SCAN_START_PIN = 2;
const int SCAN_STEP_ENABLE_PIN = 3;
const int SCAN_STEP_COMPLETE_PIN = 4;
const int SCAN_COMPLETE_PIN = 5;

const float MOTOR_STEPS_PER_REV = 200;
const float MOTOR_STEPS_PER_DEG = MOTOR_STEPS_PER_REV / 360;
const float DEG_PER_MOTOR_STEP = 360/MOTOR_STEPS_PER_REV; //added 05/30/20
const int DEFAULT_MOTOR_STEPS_TO_MOVE = 10;
char Instr[20];
//const int POSITIONING_SPEED_RPM = 20;  
const int POSITIONING_SPEED_RPM = 100;

int zeroPos;
int scanStartDeg;
int scanStartSteps; //scanStartDeg converted to steps
int scanStopDeg;
int scanStopSteps; //scanStopDeg converted to steps
int scanNumberofSteps; //added 05/27/20
int stepsToMove; //steps to move to initial position
int curMotorStepVal; //keeps track of current position, in steps
float curRelPointingAngleDeg; //keeps track of current relative pointing angle, in degrees
int curAngleStepVal; //keeps track of current table step iteration value
bool bStopPosDone = false;
int scanSpeedRpm = 6;

const int SLAVE_ADDR = 8; //added 05/30/20

void setup() 
{
	//added 05/30/20 to provide step# & angle values to Angle Scan program
	Wire.begin(SLAVE_ADDR);
	Wire.setSCL(18);
	Wire.setSCL(19);
	Wire.setClock(100000);
	Wire.onRequest(requestEvent);

	Serial.begin(115200);
	unsigned long now = millis();
	while (!Serial)
	{
		delay(10);
	}

	delay(5000); //05/28/20 delay AFTER Serial object instantiation is NECESSARY!

	Serial.print("Serial available after "); Serial.print(millis() - now); Serial.print(" millisec");

	pinMode(SCAN_START_PIN, INPUT_PULLUP);
	pinMode(SCAN_STEP_ENABLE_PIN, INPUT_PULLUP);
	pinMode(SCAN_STEP_COMPLETE_PIN, OUTPUT);
	pinMode(SCAN_COMPLETE_PIN, OUTPUT);

	//init SCAN_COMPLETE_PIN, SCAN_STEP_COMPLETE to LOW (not complete) state
	digitalWrite(SCAN_COMPLETE_PIN, LOW);
	digitalWrite(SCAN_STEP_COMPLETE_PIN, LOW);

	//added 05/26/20
	Serial.printf("Serial.printf: NEMA-17 Stepper Rotary Table Program\n");

	//get motor speed to be used
	scanSpeedRpm = GetIntegerParameter("Motor speed RPM", 6);
	myStepper.setSpeed(scanSpeedRpm);


	//set zero position
	Serial.println("Set stepper zero position.  Enter +steps for CW, -steps for CCW, Q to exit");
	while (!bStopPosDone)
	{
		while (Serial.available() == 0); //waits for input
		if (toascii(Serial.peek()) == 'Q' || toascii(Serial.peek()) == 'q')
		{
			bStopPosDone = true;
			curMotorStepVal = 0;
		}
		else
		{
			stepsToMove = GetIntegerParameter("Steps to move (- = CCW, + = CW)?", DEFAULT_MOTOR_STEPS_TO_MOVE);
			Serial.print("Steps to move = "); Serial.println(stepsToMove);
			myStepper.setSpeed(POSITIONING_SPEED_RPM);
			myStepper.step(stepsToMove);
		}
	}

	Serial.readString(); //clear the input buffer - could still have chars in it
	Serial.print("curMotorStepVal = "); Serial.println(curMotorStepVal);

	//set scan start/stop positions in degrees
	scanStartDeg = GetIntegerParameter("Scan Start Pos in Degrees Relative to Zero", -90);
	scanStopDeg = GetIntegerParameter("Scan Stop Pos in Degrees Relative to Zero", 90);
	scanNumberofSteps = GetIntegerParameter("Number of Steps", 18);
	curRelPointingAngleDeg = scanStartDeg; //added 05/30/20

	Serial.println("Run Parameters:");
	Serial.print("Speed: "); Serial.print(scanSpeedRpm); Serial.println(" RPM");
	Serial.print("Scan Start: "); Serial.print(scanStartDeg); Serial.println(" Deg");
	Serial.print("Scan Stop: "); Serial.print(scanStopDeg); Serial.println(" Deg");
	Serial.print("Scan Steps: "); Serial.println(scanNumberofSteps);
	Serial.println();

	//go to scan start pos
	scanStartSteps = (int)scanStartDeg * MOTOR_STEPS_PER_DEG;
	Serial.print("steps to move = "); Serial.println(scanStartSteps);
	Serial.printf("Before move, curMotorStepVal = %d, scanStartSteps = %d\n", curMotorStepVal, scanStartSteps);
	myStepper.step(scanStartSteps);
	curMotorStepVal += scanStartSteps;
	Serial.print("Done - curMotorStepVal = "); Serial.println(curMotorStepVal);
	Serial.printf("After move, curMotorStepVal = %d, scanStartSteps = %d\n", curMotorStepVal, scanStartSteps);

	int motorStepsPerScanStep = (int)(((int)scanStopDeg * MOTOR_STEPS_PER_DEG - curMotorStepVal) / (float)scanNumberofSteps); //05/27/20
	Serial.print("Motor Steps Per Scan Step = "); Serial.println(motorStepsPerScanStep);

	while (1)  //user has opportunity to exit after each scan
	{
		//wait for trigger
		Serial.printf("waiting for LOW on SCAN_START_PIN (pin %d) ...\n", SCAN_START_PIN);
		while (digitalRead(SCAN_START_PIN) == HIGH)
		{
			delay(100);
		}

		Serial.println("Scan Triggered - starting scan, setting SCAN_COMPLETE_PIN to LOW\n");
		digitalWrite(SCAN_COMPLETE_PIN, LOW);

		//for (curAngleStepVal = 0; curAngleStepVal < scanNumberofSteps; curAngleStepVal++)
		for (curAngleStepVal = 0; curAngleStepVal <= scanNumberofSteps; curAngleStepVal++)
		{
			curRelPointingAngleDeg = curAngleStepVal * motorStepsPerScanStep * DEG_PER_MOTOR_STEP; //added 05/30/20

			//when SCAN_STEP_ENABLE_PIN goes LOW, go to first/next step.
			while (digitalRead(SCAN_STEP_ENABLE_PIN))
			{

			}

			unsigned long now = millis();
			digitalWrite(SCAN_STEP_COMPLETE_PIN, LOW);
			Serial.printf("Scan Step %d Triggered: motor steps to move = %d\n", curAngleStepVal, motorStepsPerScanStep);
			myStepper.setSpeed(scanSpeedRpm);
			myStepper.step(motorStepsPerScanStep);
			curMotorStepVal += motorStepsPerScanStep;
			Serial.printf("Done in %lu Msec - curMotorStepVal = %d\n", millis() - now, curMotorStepVal);
			//delay(200);

			//output HIGH on SCAN_STEP_COMPLETE_PIN
			Serial.printf("Outputting HIGH on SCAN_STEP_COMPLETE_PIN\n");
			digitalWrite(SCAN_STEP_COMPLETE_PIN, HIGH);
			//delay(50);  //make the HIGH period visible on scope
		}

		//quit
		Serial.printf("Outputting HIGH on SCAN_COMPLETE_PIN (pin %d)\n", SCAN_COMPLETE_PIN);
		digitalWrite(SCAN_COMPLETE_PIN, HIGH);

		//return to start position
		stepsToMove = curMotorStepVal - scanStartSteps;
		Serial.println("Resetting for next scan.");
		Serial.printf("Before move, curMotorStepVal = %d, scanStartSteps = %d, steps to move = %d\n", 
			curMotorStepVal, scanStartSteps, stepsToMove);
		myStepper.setSpeed(POSITIONING_SPEED_RPM);
		myStepper.step(-stepsToMove);
		curMotorStepVal = scanStartSteps;
		Serial.print("Done - curMotorStepVal = "); Serial.println(curMotorStepVal);
		myStepper.setSpeed(scanSpeedRpm);

		Serial.printf("Enter any key to continue\n");
		while (!Serial.available())
		{

		}

		//consume bytes until Serial buffer is empty to avoid unintended triggers
		int incomingByte;
		while (Serial.available())
		{
			incomingByte = Serial.read();
			Serial.printf("Consuming 0x%x\n", incomingByte);
		}

	}
}


void loop()
{
}

int GetIntegerParameter(String prompt, int defaultval)
{
	int param = 0;
	bool bDone = false;

	while (!bDone)
	{
		Serial.print(prompt); Serial.print(" ("); Serial.print(defaultval); Serial.print("): ");
		while (Serial.available() == 0); //waits for input
										 //String res = Serial.readString().trim();
		String res = Serial.readString();
		res.trim();

		int reslen = res.length();
		if (reslen == 0) //user entered CR only
		{
			bDone = true;
			param = defaultval;
		}
		else
		{
			res.toCharArray(Instr, reslen + 1);
			//if (isNumeric(Instr) && atoi(Instr) >= 0)
			if (isNumeric(Instr))
			{
				param = atoi(Instr);
				bDone = true;
			}
			else
			{
				Serial.print(Instr); Serial.println(" Is invalid input - please try again");
			}
		}
	}
	Serial.println(param);
	return param;
}

// check a string to see if it is numeric and accept Decimal point
//copied from defragster's post at https://forum.pjrc.com/threads/27842-testing-if-a-string-is-numeric
bool isNumeric(char* str)
{
	byte ii = 0;
	bool RetVal = false;
	if ('-' == str[ii])
		ii++;
	while (str[ii])
	{
		if ('.' == str[ii]) {
			ii++;
			break;
		}
		if (!isdigit(str[ii])) return false;
		ii++;
		RetVal = true;
	}
	while (str[ii])
	{
		if (!isdigit(str[ii])) return false;
		ii++;
		RetVal = true;
	}
	return RetVal;
}

//05/30/20 added to report current angle step# & relative pointing angle to measurement program
void requestEvent()
{
	//send the current step# and current relative pointing angle
	Serial.printf("In requestEvent: curAngleStep = %d, curRelAngle = %2.2f\n", 
		curAngleStepVal, curAngleStepVal, curRelPointingAngleDeg, curRelPointingAngleDeg);

	I2C_writeAnything(curAngleStepVal);
	I2C_writeAnything(curRelPointingAngleDeg);
}

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Name: Teensy_NEMA17_L298N_RotaryTable.ino

Created: 5/27/2020 11:00:40 AM

Author: FRANKNEWXPS15\Frank

Teensy NEMA 17 L298N Rotary Table Program

This program controls a NEMA 17 stepper motor using an L298N motor driver. It

Takes user input to define the boresight (zero) position and the start and stop angles

in degrees relative to the zero position. Then it moves to the start position and waits

for a HIGH level on SCAN_START_PIN. After this signal is received, the motor is

stepped through to the stop position. At the stop position, the SCAN_COMPLETE_PIN is

driven HIGH.

The Stepper motor is connected to an L298N motor driver with one coil on Out1/2, and the

other coil on Out3/4. It may turn out that one coil's leads have to be reversed to match

the motor rotation direction with the program direction.

The Teensy 3.2 is connect to In1/2/3/4 via pins 8,9,10,11 although this can be changed in the

constructor below.

The NEMA 17 motor is assumed to execute 200 steps/revolution. Change the StepsPerRevolution

constant for other values.

05/27/20: Performs an angular scan over user-supplied range of angles. By default a complete scan

from start position to stop position is performed, followed by a return to the start position

However, if the STEP_ENABLE_PIN (held HIGH by default) is pulled LOW, the program will wait

until it goes HIGH before performing the next step. In this case, a scan iteration would go

as follows

Step 1 - Scan paramaters entered, motor moves to start position, waits for LOW on SCAN_START_PIN

Step 2 - Measurement program pulls SCAN_START_PIN LOW for 1 sec, then back HIGH

Step 3 - Measurement program takes a measurement & retrieves step# & angle value via I2C request

Step 4 - Measurement program pulls SCAN_STEP_ENABLE_PIN LOW

Step 5 - Motor moves to first/next step, and outputs HIGH on SCAN_STEP_COMPLETE_PIN

Step 6 - Measurement program waits for HIGH on SCAN_STEP_COMPLETE_PIN

Step 7 - Measurement program takes a measurement & retrieves step# & angle value via I2C request

Step 8 - Repeat Steps 4-7 until scan complete

Step 9 - SCAN_COMPLETE_PIN goes HIGH

//O5/30/20 Added I2C connection to pass step# & relative angle values to measurement program

#include <Stepper.h>

#include <Wire.h>

#include "I2C_Anything.h"

// change this to fit the number of steps per revolution for your motor

const int stepsPerRevolution = 200;

// initialize the stepper library on pins 8 through 11:

Stepper myStepper(stepsPerRevolution, 8, 9, 10, 11);

//08/26/17 added for scan support

const int SCAN_START_PIN = 2;

const int SCAN_STEP_ENABLE_PIN = 3;

const int SCAN_STEP_COMPLETE_PIN = 4;

const int SCAN_COMPLETE_PIN = 5;

const float MOTOR_STEPS_PER_REV = 200;

const float MOTOR_STEPS_PER_DEG = MOTOR_STEPS_PER_REV / 360;

const float DEG_PER_MOTOR_STEP = 360/MOTOR_STEPS_PER_REV; //added 05/30/20

const int DEFAULT_MOTOR_STEPS_TO_MOVE = 10;

char Instr[20];

//const int POSITIONING_SPEED_RPM = 20;

const int POSITIONING_SPEED_RPM = 100;

int zeroPos;

int scanStartDeg;

int scanStartSteps; //scanStartDeg converted to steps

int scanStopDeg;

int scanStopSteps; //scanStopDeg converted to steps

int scanNumberofSteps; //added 05/27/20

int stepsToMove; //steps to move to initial position

int curMotorStepVal; //keeps track of current position, in steps

float curRelPointingAngleDeg; //keeps track of current relative pointing angle, in degrees

int curAngleStepVal; //keeps track of current table step iteration value

bool bStopPosDone = false;

int scanSpeedRpm = 6;

const int SLAVE_ADDR = 8; //added 05/30/20

void setup()

{

//added 05/30/20 to provide step# & angle values to Angle Scan program

Wire.begin(SLAVE_ADDR);

Wire.setSCL(18);

Wire.setSCL(19);

Wire.setClock(100000);

Wire.onRequest(requestEvent);

Serial.begin(115200);

unsigned long now = millis();

while (!Serial)

{

delay(10);

}

delay(5000); //05/28/20 delay AFTER Serial object instantiation is NECESSARY!

Serial.print("Serial available after "); Serial.print(millis() - now); Serial.print(" millisec");

pinMode(SCAN_START_PIN, INPUT_PULLUP);

pinMode(SCAN_STEP_ENABLE_PIN, INPUT_PULLUP);

pinMode(SCAN_STEP_COMPLETE_PIN, OUTPUT);

pinMode(SCAN_COMPLETE_PIN, OUTPUT);

//init SCAN_COMPLETE_PIN, SCAN_STEP_COMPLETE to LOW (not complete) state

digitalWrite(SCAN_COMPLETE_PIN, LOW);

digitalWrite(SCAN_STEP_COMPLETE_PIN, LOW);

//added 05/26/20

Serial.printf("Serial.printf: NEMA-17 Stepper Rotary Table Program\n");

//get motor speed to be used

scanSpeedRpm = GetIntegerParameter("Motor speed RPM", 6);

myStepper.setSpeed(scanSpeedRpm);

//set zero position

Serial.println("Set stepper zero position. Enter +steps for CW, -steps for CCW, Q to exit");

while (!bStopPosDone)

{

while (Serial.available() == 0); //waits for input

if (toascii(Serial.peek()) == 'Q' || toascii(Serial.peek()) == 'q')

{

bStopPosDone = true;

curMotorStepVal = 0;

}

else

{

stepsToMove = GetIntegerParameter("Steps to move (- = CCW, + = CW)?", DEFAULT_MOTOR_STEPS_TO_MOVE);

Serial.print("Steps to move = "); Serial.println(stepsToMove);

myStepper.setSpeed(POSITIONING_SPEED_RPM);

myStepper.step(stepsToMove);

}

Serial.readString(); //clear the input buffer - could still have chars in it

Serial.print("curMotorStepVal = "); Serial.println(curMotorStepVal);

//set scan start/stop positions in degrees

scanStartDeg = GetIntegerParameter("Scan Start Pos in Degrees Relative to Zero", -90);

scanStopDeg = GetIntegerParameter("Scan Stop Pos in Degrees Relative to Zero", 90);

scanNumberofSteps = GetIntegerParameter("Number of Steps", 18);

curRelPointingAngleDeg = scanStartDeg; //added 05/30/20

Serial.println("Run Parameters:");

Serial.print("Speed: "); Serial.print(scanSpeedRpm); Serial.println(" RPM");

Serial.print("Scan Start: "); Serial.print(scanStartDeg); Serial.println(" Deg");

Serial.print("Scan Stop: "); Serial.print(scanStopDeg); Serial.println(" Deg");

Serial.print("Scan Steps: "); Serial.println(scanNumberofSteps);

Serial.println();

//go to scan start pos

scanStartSteps = (int)scanStartDeg * MOTOR_STEPS_PER_DEG;

Serial.print("steps to move = "); Serial.println(scanStartSteps);

Serial.printf("Before move, curMotorStepVal = %d, scanStartSteps = %d\n", curMotorStepVal, scanStartSteps);

myStepper.step(scanStartSteps);

curMotorStepVal += scanStartSteps;

Serial.print("Done - curMotorStepVal = "); Serial.println(curMotorStepVal);

Serial.printf("After move, curMotorStepVal = %d, scanStartSteps = %d\n", curMotorStepVal, scanStartSteps);

int motorStepsPerScanStep = (int)(((int)scanStopDeg * MOTOR_STEPS_PER_DEG - curMotorStepVal) / (float)scanNumberofSteps); //05/27/20

Serial.print("Motor Steps Per Scan Step = "); Serial.println(motorStepsPerScanStep);

while (1) //user has opportunity to exit after each scan

{

//wait for trigger

Serial.printf("waiting for LOW on SCAN_START_PIN (pin %d) ...\n", SCAN_START_PIN);

while (digitalRead(SCAN_START_PIN) == HIGH)

{

delay(100);

}

Serial.println("Scan Triggered - starting scan, setting SCAN_COMPLETE_PIN to LOW\n");

digitalWrite(SCAN_COMPLETE_PIN, LOW);

//for (curAngleStepVal = 0; curAngleStepVal < scanNumberofSteps; curAngleStepVal++)

for (curAngleStepVal = 0; curAngleStepVal <= scanNumberofSteps; curAngleStepVal++)

{

curRelPointingAngleDeg = curAngleStepVal * motorStepsPerScanStep * DEG_PER_MOTOR_STEP; //added 05/30/20

//when SCAN_STEP_ENABLE_PIN goes LOW, go to first/next step.

while (digitalRead(SCAN_STEP_ENABLE_PIN))

{

}

unsigned long now = millis();

digitalWrite(SCAN_STEP_COMPLETE_PIN, LOW);

Serial.printf("Scan Step %d Triggered: motor steps to move = %d\n", curAngleStepVal, motorStepsPerScanStep);

myStepper.setSpeed(scanSpeedRpm);

myStepper.step(motorStepsPerScanStep);

curMotorStepVal += motorStepsPerScanStep;

Serial.printf("Done in %lu Msec - curMotorStepVal = %d\n", millis() - now, curMotorStepVal);

//delay(200);

//output HIGH on SCAN_STEP_COMPLETE_PIN

Serial.printf("Outputting HIGH on SCAN_STEP_COMPLETE_PIN\n");

digitalWrite(SCAN_STEP_COMPLETE_PIN, HIGH);

//delay(50); //make the HIGH period visible on scope

}

//quit

Serial.printf("Outputting HIGH on SCAN_COMPLETE_PIN (pin %d)\n", SCAN_COMPLETE_PIN);

digitalWrite(SCAN_COMPLETE_PIN, HIGH);

//return to start position

stepsToMove = curMotorStepVal - scanStartSteps;

Serial.println("Resetting for next scan.");

Serial.printf("Before move, curMotorStepVal = %d, scanStartSteps = %d, steps to move = %d\n",

curMotorStepVal, scanStartSteps, stepsToMove);

myStepper.setSpeed(POSITIONING_SPEED_RPM);

myStepper.step(-stepsToMove);

curMotorStepVal = scanStartSteps;

Serial.print("Done - curMotorStepVal = "); Serial.println(curMotorStepVal);

myStepper.setSpeed(scanSpeedRpm);

Serial.printf("Enter any key to continue\n");

while (!Serial.available())

{

}

//consume bytes until Serial buffer is empty to avoid unintended triggers

int incomingByte;

while (Serial.available())

{

incomingByte = Serial.read();

Serial.printf("Consuming 0x%x\n", incomingByte);

}

void loop()

{

}

int GetIntegerParameter(String prompt, int defaultval)

{

int param = 0;

bool bDone = false;

while (!bDone)

{

Serial.print(prompt); Serial.print(" ("); Serial.print(defaultval); Serial.print("): ");

while (Serial.available() == 0); //waits for input

//String res = Serial.readString().trim();

String res = Serial.readString();

res.trim();

int reslen = res.length();

if (reslen == 0) //user entered CR only

{

bDone = true;

param = defaultval;

}

else

{

res.toCharArray(Instr, reslen + 1);

//if (isNumeric(Instr) && atoi(Instr) >= 0)

if (isNumeric(Instr))

{

param = atoi(Instr);

bDone = true;

}

else

{

Serial.print(Instr); Serial.println(" Is invalid input - please try again");

}

Serial.println(param);

return param;

}

// check a string to see if it is numeric and accept Decimal point

//copied from defragster's post at https://forum.pjrc.com/threads/27842-testing-if-a-string-is-numeric

bool isNumeric(char* str)

{

byte ii = 0;

bool RetVal = false;

if ('-' == str[ii])

ii++;

while (str[ii])

{

if ('.' == str[ii]) {

ii++;

break;

}

if (!isdigit(str[ii])) return false;

ii++;

RetVal = true;

}

while (str[ii])

{

if (!isdigit(str[ii])) return false;

ii++;

RetVal = true;

}

return RetVal;

}

//05/30/20 added to report current angle step# & relative pointing angle to measurement program

void requestEvent()

{

//send the current step# and current relative pointing angle

Serial.printf("In requestEvent: curAngleStep = %d, curRelAngle = %2.2f\n",

curAngleStepVal, curAngleStepVal, curRelPointingAngleDeg, curRelPointingAngleDeg);

I2C_writeAnything(curAngleStepVal);

I2C_writeAnything(curRelPointingAngleDeg);

}

And the hardware layout:

I couldn’t find any information about winding polarity for this particular NEMA 17 stepper, so it was sort of a crapshoot as to which way the motor was going to turn for a nominal CW or CCW input to the program. As it turned out, I had to reverse one set of wires on the L298N to get the stepper to turn in the correct direction.

Companion Measurement System

For the companion measurement system, I used a Teensy 3.5 micro-controller, as I needed to connect to the VL53L0X ‘Time of Flight’ sensors and the Rotary Table program/micro-controller via I2C, and The Teensy 3.5 has provisions for up to three separate I2C busses (Wire, Wire1 & Wire2). Although it would be possible to put everything on one I2C bus, I wanted to isolate the two ‘sides’ (the rotary table control side, and the sensor control side). This dual-IC2 bus arrangement is also the way I plan to integrate the VL53L0X sensor arrays into Wall-E2, my autonomous wall-following robot, so this will give me a chance to work out the bugs on a smaller scale.

Here’s the wiring diagram:

Wiring diagram for the companion measurement system, with triple VL53L0X ToF sensors

And the software:

/*
    Name:       TeensyTripleVL53L0XAngleScanV1.ino
    Created:	5/28/2020 12:15:50 PM
    Author:     FRANKNEWXPS15\Frank
*/


/*
This program is derived from Teensy_Triple_VL53L0X_V2.ino.  It uses the 
Teensy_NEMA17_L298N_RotaryTable program to perform triple VL53L0X
measurements over a range of angles. 

Teensy_NEMA17_L298N_RotaryTable program:
Performs an angular scan over user-supplied range of angles.  By default a complete scan
from start position to stop position is performed, followed by a return to the start position
However, if the STEP_ENABLE_PIN (held HIGH by default) is pulled LOW, the program will wait
until it goes HIGH before performing the next step.  In this case, a scan iteration would go
as follows

    Step 1 - Scan paramaters entered, motor moves to start position, waits for LOW on SCAN_START_PIN
    Step 2 - Measurement program pulls SCAN_START_PIN LOW for 1 sec, then back HIGH
    Step 3 - Measurement program takes a measurement & retrieves step# & angle value via I2C request
    Step 4 - Measurement program pulls SCAN_STEP_ENABLE_PIN LOW
    Step 5 - Motor moves to first/next step, and outputs HIGH on SCAN_STEP_COMPLETE_PIN
    Step 6 - Measurement program waits for HIGH on SCAN_STEP_COMPLETE_PIN
    Step 7 - Measurement program takes a measurement & retrieves step# & angle value via I2C request
    Step 8 - Repeat Steps 4-7 until scan complete
    Step 9 - SCAN_COMPLETE_PIN goes HIGH

At present (05/28/20) the rotary table pin assignments are:
SCAN_START_PIN = 2
SCAN_STEP_ENABLE_PIN = 3
SCAN_STEP_COMPLETE_PIN = 4
SCAN_COMPLETE_PIN = 5
*/


/* This code copied from the following post on the Adafruit forum:
https://forums.adafruit.com/viewtopic.php?f=19&t=164589&p=808693&hilit=vl53l0x#p808693

And adapted to use it on the Wire1 I2C bus on a Teensy 3.5
*/


#include <Wire.h>
#include "Adafruit_VL53L0X.h"
#include "I2C_Anything.h"

Adafruit_VL53L0X lidar_RF = Adafruit_VL53L0X(); //Right-front LIDAR (angled 30 deg forward)
Adafruit_VL53L0X lidar_RC = Adafruit_VL53L0X(); //Center LIDAR
Adafruit_VL53L0X lidar_RR = Adafruit_VL53L0X(); //Right-rear LIDAR (angled 30 deg rearward)


//XSHUT required for I2C address init 
const int RF_XSHUT_PIN = 23;
const int RC_XSHUT_PIN = 22;
const int RR_XSHUT_PIN = 21;

const int RED_LASER_PIN = 0;

const int MAX_LIDAR_RANGE_MM = 1000; //make it obvious when nearest object is out of range

uint16_t RF_Dist_mm;
uint16_t RC_Dist_mm;
uint16_t RR_Dist_mm;
float SteeringVal; //mvd here 05/30/20

//Rotary Scan Table Connections:
const int SCAN_START_PIN = 2; //connect to table SCAN_START_PIN
const int SCAN_STEP_ENABLE_PIN = 3;//connect to table SCAN_STEP_ENABLE_PIN
const int SCAN_STEP_COMPLETE_PIN = 4;//connect to table SCAN_STEP_COMPLETE_PIN
const int SCAN_COMPLETE_PIN = 5;//connect to table SCAN_COMPLETE_PIN

 //added 05/30/20 to retrieve values from rotary table program
const int SLAVE_ADDR = 8;
int curStepVal = 0;
float curAngleDeg = 0;


void setup()
{

    //added 05/30/20 to retrieve step# & angle values from rotary table program
    Wire.begin();
    Wire.setClock(100000);
    Wire.setSCL(18);
    Wire.setSDA(19);

    Serial.begin(115200); //Teensy ignores rate parameter


    // wait until serial port opens for native USB devices
    while (!Serial)
    {
        delay(1);
    }

    delay(5000); //05/28/20 - this delay is necessary AFTER Serial instantiation!

    Serial.printf("Teensy Triple VL53L0X Angle Scan Program\n");

    pinMode(RF_XSHUT_PIN, OUTPUT);
    pinMode(RC_XSHUT_PIN, OUTPUT);
    pinMode(RR_XSHUT_PIN, OUTPUT);

    pinMode(RED_LASER_PIN, OUTPUT);

    //Rotary Scan Table Connections:
    pinMode(SCAN_START_PIN, OUTPUT);
    pinMode(SCAN_STEP_ENABLE_PIN, OUTPUT);
    pinMode(SCAN_STEP_COMPLETE_PIN, INPUT_PULLDOWN);
    pinMode(SCAN_COMPLETE_PIN, INPUT_PULLUP);

    //Initialize table connection states
    digitalWrite(SCAN_START_PIN, HIGH); //disables scans
    digitalWrite(SCAN_STEP_ENABLE_PIN, HIGH); //disables steps  

    //initialize 3 LIDAR sensors
    // 1. Reset all sensors by setting all of their XSHUT pins low for delay(10), then set
    //    all XSHUT high to bring out of reset
    digitalWrite(RF_XSHUT_PIN, LOW);
    delay(10);
    digitalWrite(RC_XSHUT_PIN, LOW);
    delay(10);
    digitalWrite(RR_XSHUT_PIN, LOW);
    delay(10);
    digitalWrite(RF_XSHUT_PIN, HIGH);
    digitalWrite(RC_XSHUT_PIN, HIGH);
    digitalWrite(RR_XSHUT_PIN, HIGH);

    // 2. Keep sensor #1 awake by keeping XSHUT pin high, and put all other sensors into
    //    shutdown by pulling XSHUT pins low
    digitalWrite(RC_XSHUT_PIN, LOW);
    digitalWrite(RR_XSHUT_PIN, LOW);

    // 3. Initialize sensor #1 
    if (!lidar_RF.begin(VL53L0X_I2C_ADDR + 1, false, &Wire1))
    {
        Serial.println(F("Failed to boot lidar_RF"));
        while (1);
    }

    // 4. Keep sensor #1 awake, and now bring sensor #2 out of reset by setting its XSHUT pin high.
    // 5. Initialize sensor #2 with lox.begin(new_i2c_address) Pick any number but 0x29 and whatever
    //    you set the first sensor to
    digitalWrite(RC_XSHUT_PIN, HIGH);
    if (!lidar_RC.begin(VL53L0X_I2C_ADDR + 2, false, &Wire1))
    {
        Serial.println(F("Failed to boot lidar_RC"));
        while (1);
    }

    // 6. Repeat for last sensor.
    digitalWrite(RR_XSHUT_PIN, HIGH);
    if (!lidar_RR.begin(VL53L0X_I2C_ADDR + 3, false, &Wire1))
    {
        Serial.println(F("Failed to boot lidar_RR"));
        while (1);
    }

    //turn the laser OFF
    digitalWrite(RED_LASER_PIN, LOW);

    Serial.printf("\nInit complete\n \n");

    Serial.printf("\nWhen the Rotary Table is set up and ready to go, send any key\n \n");


    while (!Serial.available())
    {
        Serial.printf("Nothing yet...\n");
        delay(1000);
    }

    //consume bytes until Serial buffer is empty to avoid unintended triggers
    int incomingByte;
    while (Serial.available())
    {
        incomingByte = Serial.read();
        Serial.printf("Consuming 0x%x\n",incomingByte);
    }

    ////05/23/20 experiment with accessing API functions
    //VL53L0X_Dev_t RightFrontDevice = lidar_RF.GetDeviceHandle();
    //VL53L0X_DeviceInfo_t RightFrontDeviceInfo = lidar_RF.GetDeviceInfo();
    //Serial.printf("Device Info for Right Front Sensor\n");
    //Serial.printf("\tName = %s\n\tType = %s\n\tProdID = %s\n\tType Number = %d\n\tMajor Rev = %d\n\tMinor Rev = %d\n \n",
    //    RightFrontDeviceInfo.Name, RightFrontDeviceInfo.Type,
    //    RightFrontDeviceInfo.ProductId, RightFrontDeviceInfo.ProductType,
    //    RightFrontDeviceInfo.ProductRevisionMajor, RightFrontDeviceInfo.ProductRevisionMinor);

    ////get measurement timing budget?
    //prog_uint32_t MeasBudgetUSec;
    //VL53L0X_Error ApiError = VL53L0X_GetMeasurementTimingBudgetMicroSeconds(&RightFrontDevice, &MeasBudgetUSec);
    //Serial.printf("Right Front Measurement Budget (uSec) = %d\n", MeasBudgetUSec);
    //delay(1000);
    //Serial.printf("Changing budget from %d to %d....\n", MeasBudgetUSec, 2 * MeasBudgetUSec);
    //delay(1000);
    //MeasBudgetUSec = 2 * MeasBudgetUSec;
    //ApiError = VL53L0X_SetMeasurementTimingBudgetMicroSeconds(&RightFrontDevice, MeasBudgetUSec);
    //Serial.printf("Right Front Measurement Budget (uSec) Now = %d\n \n", MeasBudgetUSec);

    bool bDone = false; 
    while (!bDone)
    {
        //init controls to 'disabled' state
        digitalWrite(SCAN_STEP_ENABLE_PIN, HIGH); //init to 'steps disabled'
        digitalWrite(SCAN_START_PIN, HIGH); //init to 'scan disabled'


        Serial.printf("Starting Angle Scan...\n \n");
        Serial.printf("Msec\tStep#\tRelDeg\tFront\tCenter\tRear\tSteer\n"); //rev 5/30/20 to include step# & rel ptng angle

        //Tell the table to start the scan
        digitalWrite(SCAN_START_PIN, LOW); //trigger the scan
        delay(1000); //long enough for table to see it
        digitalWrite(SCAN_START_PIN, HIGH); //reset the trigger


        //do until the scan is complete
        while (!digitalRead(SCAN_COMPLETE_PIN))
        {
            //take measurement
            GetVL53L0XValues();

            //05/30/20 get current step# & relative pointing angle
            Wire.requestFrom(SLAVE_ADDR, sizeof(curStepVal) + sizeof(curAngleDeg));
            I2C_readAnything(curStepVal);
            I2C_readAnything(curAngleDeg);

            Serial.printf("%lu\t%d\t%3.2f\t%d\t%d\t%d\t%3.2f\n", 
                millis(),curStepVal,curAngleDeg,
                RF_Dist_mm, RC_Dist_mm, RR_Dist_mm, SteeringVal);

            digitalWrite(SCAN_STEP_ENABLE_PIN, LOW); //trigger table to step to next position
            delay(100); //give rotary table time to reset SCAN_STEP_COMPLETE_PIN state

            //wait for step to complete
            while (!digitalRead(SCAN_STEP_COMPLETE_PIN))
            {
                //Serial.printf("Waiting for SCAN_STEP_COMPLETE_PIN to go HIGH\n");
                //delay(1000);

            }

            //disable steps
            digitalWrite(SCAN_STEP_ENABLE_PIN, HIGH); //disable further steps
            delay(50); //05/31/20 give SCAN_COMPLETE_PIN a chance to go HIGH before next measurement
        }

        Serial.printf("SCAN_COMPLETE_PIN HIGH Received - Scan is Complete!\n");

        Serial.printf("Enter Q to quit, anything else for another scan\n");
        while (!Serial.available())
        {
            Serial.printf("nothing yet....\n");
            delay(1000);
        }

        incomingByte = Serial.read();
        Serial.printf("I received: 0x%0x\n",incomingByte);

        if (incomingByte == 0x51 || incomingByte == 0x71)
        {
            Serial.printf("Stopping Program - Goodbye!\n");
            while (true)
            {

            }
        }
        else
        {
            //consume any remaining bytes in buffer
            while (Serial.available() > 0)
            {
                Serial.read();
            }
            Serial.printf("Starting another scan...\n");
        }
    }
}

void loop()
{
}

void GetVL53L0XValues()
{
    //Serial.printf("In GetVL53L0XValues()\n");
    VL53L0X_RangingMeasurementData_t measure;

    //turn the laser ON
    digitalWrite(RED_LASER_PIN, HIGH);

    lidar_RF.rangingTest(&measure, false); // pass in 'true' to get debug data printout!
    if (measure.RangeStatus != 4)  // phase failures have incorrect data
    {
        RF_Dist_mm = measure.RangeMilliMeter;
        if (RF_Dist_mm > MAX_LIDAR_RANGE_MM) RF_Dist_mm = MAX_LIDAR_RANGE_MM;
    }
    else RF_Dist_mm = 0;

    lidar_RC.rangingTest(&measure, false); // pass in 'true' to get debug data printout!
    if (measure.RangeStatus != 4)  // phase failures have incorrect data
    {
        RC_Dist_mm = measure.RangeMilliMeter;
        if (RC_Dist_mm > MAX_LIDAR_RANGE_MM) RC_Dist_mm = MAX_LIDAR_RANGE_MM;
    }
    else RC_Dist_mm = 0;

    lidar_RR.rangingTest(&measure, false); // pass in 'true' to get debug data printout!
    if (measure.RangeStatus != 4)  // phase failures have incorrect data
    {
        RR_Dist_mm = measure.RangeMilliMeter;
        if (RR_Dist_mm > MAX_LIDAR_RANGE_MM) RR_Dist_mm = MAX_LIDAR_RANGE_MM;
    }
    else RR_Dist_mm = 0;

    SteeringVal = (RF_Dist_mm - RR_Dist_mm) / (float)RC_Dist_mm;

    //turn the laser OFF
    digitalWrite(RED_LASER_PIN, LOW);

    //delay(100);
}

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Name: TeensyTripleVL53L0XAngleScanV1.ino

Created: 5/28/2020 12:15:50 PM

Author: FRANKNEWXPS15\Frank

This program is derived from Teensy_Triple_VL53L0X_V2.ino. It uses the

Teensy_NEMA17_L298N_RotaryTable program to perform triple VL53L0X

measurements over a range of angles.

Teensy_NEMA17_L298N_RotaryTable program:

Performs an angular scan over user-supplied range of angles. By default a complete scan

from start position to stop position is performed, followed by a return to the start position

However, if the STEP_ENABLE_PIN (held HIGH by default) is pulled LOW, the program will wait

until it goes HIGH before performing the next step. In this case, a scan iteration would go

as follows

Step 1 - Scan paramaters entered, motor moves to start position, waits for LOW on SCAN_START_PIN

Step 2 - Measurement program pulls SCAN_START_PIN LOW for 1 sec, then back HIGH

Step 3 - Measurement program takes a measurement & retrieves step# & angle value via I2C request

Step 4 - Measurement program pulls SCAN_STEP_ENABLE_PIN LOW

Step 5 - Motor moves to first/next step, and outputs HIGH on SCAN_STEP_COMPLETE_PIN

Step 6 - Measurement program waits for HIGH on SCAN_STEP_COMPLETE_PIN

Step 7 - Measurement program takes a measurement & retrieves step# & angle value via I2C request

Step 8 - Repeat Steps 4-7 until scan complete

Step 9 - SCAN_COMPLETE_PIN goes HIGH

At present (05/28/20) the rotary table pin assignments are:

SCAN_START_PIN = 2

SCAN_STEP_ENABLE_PIN = 3

SCAN_STEP_COMPLETE_PIN = 4

SCAN_COMPLETE_PIN = 5

/* This code copied from the following post on the Adafruit forum:

https://forums.adafruit.com/viewtopic.php?f=19&t=164589&p=808693&hilit=vl53l0x#p808693

And adapted to use it on the Wire1 I2C bus on a Teensy 3.5

#include <Wire.h>

#include "Adafruit_VL53L0X.h"

#include "I2C_Anything.h"

Adafruit_VL53L0X lidar_RF = Adafruit_VL53L0X(); //Right-front LIDAR (angled 30 deg forward)

Adafruit_VL53L0X lidar_RC = Adafruit_VL53L0X(); //Center LIDAR

Adafruit_VL53L0X lidar_RR = Adafruit_VL53L0X(); //Right-rear LIDAR (angled 30 deg rearward)

//XSHUT required for I2C address init

const int RF_XSHUT_PIN = 23;

const int RC_XSHUT_PIN = 22;

const int RR_XSHUT_PIN = 21;

const int RED_LASER_PIN = 0;

const int MAX_LIDAR_RANGE_MM = 1000; //make it obvious when nearest object is out of range

uint16_t RF_Dist_mm;

uint16_t RC_Dist_mm;

uint16_t RR_Dist_mm;

float SteeringVal; //mvd here 05/30/20

//Rotary Scan Table Connections:

const int SCAN_START_PIN = 2; //connect to table SCAN_START_PIN

const int SCAN_STEP_ENABLE_PIN = 3;//connect to table SCAN_STEP_ENABLE_PIN

const int SCAN_STEP_COMPLETE_PIN = 4;//connect to table SCAN_STEP_COMPLETE_PIN

const int SCAN_COMPLETE_PIN = 5;//connect to table SCAN_COMPLETE_PIN

//added 05/30/20 to retrieve values from rotary table program

const int SLAVE_ADDR = 8;

int curStepVal = 0;

float curAngleDeg = 0;

void setup()

{

//added 05/30/20 to retrieve step# & angle values from rotary table program

Wire.begin();

Wire.setClock(100000);

Wire.setSCL(18);

Wire.setSDA(19);

Serial.begin(115200); //Teensy ignores rate parameter

// wait until serial port opens for native USB devices

while (!Serial)

{

delay(1);

}

delay(5000); //05/28/20 - this delay is necessary AFTER Serial instantiation!

Serial.printf("Teensy Triple VL53L0X Angle Scan Program\n");

pinMode(RF_XSHUT_PIN, OUTPUT);

pinMode(RC_XSHUT_PIN, OUTPUT);

pinMode(RR_XSHUT_PIN, OUTPUT);

pinMode(RED_LASER_PIN, OUTPUT);

//Rotary Scan Table Connections:

pinMode(SCAN_START_PIN, OUTPUT);

pinMode(SCAN_STEP_ENABLE_PIN, OUTPUT);

pinMode(SCAN_STEP_COMPLETE_PIN, INPUT_PULLDOWN);

pinMode(SCAN_COMPLETE_PIN, INPUT_PULLUP);

//Initialize table connection states

digitalWrite(SCAN_START_PIN, HIGH); //disables scans

digitalWrite(SCAN_STEP_ENABLE_PIN, HIGH); //disables steps

//initialize 3 LIDAR sensors

// 1. Reset all sensors by setting all of their XSHUT pins low for delay(10), then set

// all XSHUT high to bring out of reset

digitalWrite(RF_XSHUT_PIN, LOW);

delay(10);

digitalWrite(RC_XSHUT_PIN, LOW);

delay(10);

digitalWrite(RR_XSHUT_PIN, LOW);

delay(10);

digitalWrite(RF_XSHUT_PIN, HIGH);

digitalWrite(RC_XSHUT_PIN, HIGH);

digitalWrite(RR_XSHUT_PIN, HIGH);

// 2. Keep sensor #1 awake by keeping XSHUT pin high, and put all other sensors into

// shutdown by pulling XSHUT pins low

digitalWrite(RC_XSHUT_PIN, LOW);

digitalWrite(RR_XSHUT_PIN, LOW);

// 3. Initialize sensor #1

if (!lidar_RF.begin(VL53L0X_I2C_ADDR + 1, false, &Wire1))

{

Serial.println(F("Failed to boot lidar_RF"));

while (1);

}

// 4. Keep sensor #1 awake, and now bring sensor #2 out of reset by setting its XSHUT pin high.

// 5. Initialize sensor #2 with lox.begin(new_i2c_address) Pick any number but 0x29 and whatever

// you set the first sensor to

digitalWrite(RC_XSHUT_PIN, HIGH);

if (!lidar_RC.begin(VL53L0X_I2C_ADDR + 2, false, &Wire1))

{

Serial.println(F("Failed to boot lidar_RC"));

while (1);

}

// 6. Repeat for last sensor.

digitalWrite(RR_XSHUT_PIN, HIGH);

if (!lidar_RR.begin(VL53L0X_I2C_ADDR + 3, false, &Wire1))

{

Serial.println(F("Failed to boot lidar_RR"));

while (1);

}

//turn the laser OFF

digitalWrite(RED_LASER_PIN, LOW);

Serial.printf("\nInit complete\n \n");

Serial.printf("\nWhen the Rotary Table is set up and ready to go, send any key\n \n");

while (!Serial.available())

{

Serial.printf("Nothing yet...\n");

delay(1000);

}

//consume bytes until Serial buffer is empty to avoid unintended triggers

int incomingByte;

while (Serial.available())

{

incomingByte = Serial.read();

Serial.printf("Consuming 0x%x\n",incomingByte);

}

////05/23/20 experiment with accessing API functions

//VL53L0X_Dev_t RightFrontDevice = lidar_RF.GetDeviceHandle();

//VL53L0X_DeviceInfo_t RightFrontDeviceInfo = lidar_RF.GetDeviceInfo();

//Serial.printf("Device Info for Right Front Sensor\n");

//Serial.printf("\tName = %s\n\tType = %s\n\tProdID = %s\n\tType Number = %d\n\tMajor Rev = %d\n\tMinor Rev = %d\n \n",

// RightFrontDeviceInfo.Name, RightFrontDeviceInfo.Type,

// RightFrontDeviceInfo.ProductId, RightFrontDeviceInfo.ProductType,

// RightFrontDeviceInfo.ProductRevisionMajor, RightFrontDeviceInfo.ProductRevisionMinor);

////get measurement timing budget?

//prog_uint32_t MeasBudgetUSec;

//VL53L0X_Error ApiError = VL53L0X_GetMeasurementTimingBudgetMicroSeconds(&RightFrontDevice, &MeasBudgetUSec);

//Serial.printf("Right Front Measurement Budget (uSec) = %d\n", MeasBudgetUSec);

//delay(1000);

//Serial.printf("Changing budget from %d to %d....\n", MeasBudgetUSec, 2 * MeasBudgetUSec);

//delay(1000);

//MeasBudgetUSec = 2 * MeasBudgetUSec;

//ApiError = VL53L0X_SetMeasurementTimingBudgetMicroSeconds(&RightFrontDevice, MeasBudgetUSec);

//Serial.printf("Right Front Measurement Budget (uSec) Now = %d\n \n", MeasBudgetUSec);

bool bDone = false;

while (!bDone)

{

//init controls to 'disabled' state

digitalWrite(SCAN_STEP_ENABLE_PIN, HIGH); //init to 'steps disabled'

digitalWrite(SCAN_START_PIN, HIGH); //init to 'scan disabled'

Serial.printf("Starting Angle Scan...\n \n");

Serial.printf("Msec\tStep#\tRelDeg\tFront\tCenter\tRear\tSteer\n"); //rev 5/30/20 to include step# & rel ptng angle

//Tell the table to start the scan

digitalWrite(SCAN_START_PIN, LOW); //trigger the scan

delay(1000); //long enough for table to see it

digitalWrite(SCAN_START_PIN, HIGH); //reset the trigger

//do until the scan is complete

while (!digitalRead(SCAN_COMPLETE_PIN))

{

//take measurement

GetVL53L0XValues();

//05/30/20 get current step# & relative pointing angle

Wire.requestFrom(SLAVE_ADDR, sizeof(curStepVal) + sizeof(curAngleDeg));

I2C_readAnything(curStepVal);

I2C_readAnything(curAngleDeg);

Serial.printf("%lu\t%d\t%3.2f\t%d\t%d\t%d\t%3.2f\n",

millis(),curStepVal,curAngleDeg,

RF_Dist_mm, RC_Dist_mm, RR_Dist_mm, SteeringVal);

digitalWrite(SCAN_STEP_ENABLE_PIN, LOW); //trigger table to step to next position

delay(100); //give rotary table time to reset SCAN_STEP_COMPLETE_PIN state

//wait for step to complete

while (!digitalRead(SCAN_STEP_COMPLETE_PIN))

{

//Serial.printf("Waiting for SCAN_STEP_COMPLETE_PIN to go HIGH\n");

//delay(1000);

}

//disable steps

digitalWrite(SCAN_STEP_ENABLE_PIN, HIGH); //disable further steps

delay(50); //05/31/20 give SCAN_COMPLETE_PIN a chance to go HIGH before next measurement

}

Serial.printf("SCAN_COMPLETE_PIN HIGH Received - Scan is Complete!\n");

Serial.printf("Enter Q to quit, anything else for another scan\n");

while (!Serial.available())

{

Serial.printf("nothing yet....\n");

delay(1000);

}

incomingByte = Serial.read();

Serial.printf("I received: 0x%0x\n",incomingByte);

if (incomingByte == 0x51 || incomingByte == 0x71)

{

Serial.printf("Stopping Program - Goodbye!\n");

while (true)

{

}

else

{

//consume any remaining bytes in buffer

while (Serial.available() > 0)

{

Serial.read();

}

Serial.printf("Starting another scan...\n");

}

void loop()

{

}

void GetVL53L0XValues()

{

//Serial.printf("In GetVL53L0XValues()\n");

VL53L0X_RangingMeasurementData_t measure;

//turn the laser ON

digitalWrite(RED_LASER_PIN, HIGH);

lidar_RF.rangingTest(&measure, false); // pass in 'true' to get debug data printout!

if (measure.RangeStatus != 4) // phase failures have incorrect data

{

RF_Dist_mm = measure.RangeMilliMeter;

if (RF_Dist_mm > MAX_LIDAR_RANGE_MM) RF_Dist_mm = MAX_LIDAR_RANGE_MM;

}

else RF_Dist_mm = 0;

lidar_RC.rangingTest(&measure, false); // pass in 'true' to get debug data printout!

if (measure.RangeStatus != 4) // phase failures have incorrect data

{

RC_Dist_mm = measure.RangeMilliMeter;

if (RC_Dist_mm > MAX_LIDAR_RANGE_MM) RC_Dist_mm = MAX_LIDAR_RANGE_MM;

}

else RC_Dist_mm = 0;

lidar_RR.rangingTest(&measure, false); // pass in 'true' to get debug data printout!

if (measure.RangeStatus != 4) // phase failures have incorrect data

{

RR_Dist_mm = measure.RangeMilliMeter;

if (RR_Dist_mm > MAX_LIDAR_RANGE_MM) RR_Dist_mm = MAX_LIDAR_RANGE_MM;

}

else RR_Dist_mm = 0;

SteeringVal = (RF_Dist_mm - RR_Dist_mm) / (float)RC_Dist_mm;

//turn the laser OFF

digitalWrite(RED_LASER_PIN, LOW);

//delay(100);

}

and the hardware setup:

Rotary table Teensy 3.2 in foreground with L298N motor controller. Teensy 3.5 measurement controller in middle, with plugboard , NEMA 17 stepper motor and triple VL53L0X array in background

Here’s a short video showing a typical measurement scan:

And here’s a typical output:

Starting Angle Scan...
 
Msec	Step#	RelDeg	Front	Center	Rear	Steer
94128	0	0.00	361	416	507	-0.35
94498	1	9.00	372	418	507	-0.32
94868	2	18.00	372	413	510	-0.33
95237	3	27.00	368	418	506	-0.33
95607	4	36.00	368	420	510	-0.34
95976	5	45.00	376	420	508	-0.31
96346	6	54.00	365	418	502	-0.33
SCAN_COMPLETE_PIN HIGH Received - Scan is Complete!
Enter Q to quit, anything else for another scan

Starting Angle Scan...

Msec Step# RelDeg Front Center Rear Steer

94128 0 0.00 361 416 507 -0.35

94498 1 9.00 372 418 507 -0.32

94868 2 18.00 372 413 510 -0.33

95237 3 27.00 368 418 506 -0.33

95607 4 36.00 368 420 510 -0.34

95976 5 45.00 376 420 508 -0.31

96346 6 54.00 365 418 502 -0.33

SCAN_COMPLETE_PIN HIGH Received - Scan is Complete!

Enter Q to quit, anything else for another scan

In the above output, the ‘Step#’ and ‘RelDeg’ values were obtained from the rotary scanner program via the primary I2C bus, while the ‘Front’, ‘Center’, and ‘Rear’ distance values were obtained from the three VL53L0X ToF sensors via the secondary I2C bus. The ‘Steer’ value was calculated locally by the measurement controller.

Upgrade to Micro-step capable motor driver:

After getting everything to work properly, I was a bit puzzled why I wasn’t getting the correct relative angle values back from the rotary table subsystem. After a while I figured out that the reason was that the rotary table program calculates an integer number of steps based on the total angle change divided by the number of scan steps, and, in general, the result won’t be exact. When moving from one scan step to the next the motor moves an integer number of steps, which in general will not be the desired angle change. For a 60 degree scan arc with 6 steps, the desired angle/scan step is 10 deg, and at 1.8 deg/step this would result in 10/1.8 = 5.5555… motor steps/scan step. This value gets truncated to 5 motor steps/scan step, which results in each scan step being 1.8 deg/step * 5 steps = 9 deg/scan step. So, instead of the scan steps occurring at 0, 10, 20, 30, 40, 50, 60 deg, they are at 0, 9, 18, 27, 36, 45, and 54 deg, and the last 6 deg of scan is never covered.

The answer to this problem is to use a motor with more than 200 steps/rev, or to use a driver that can generate micro-steps, effectively increasing the angular resolution of the scan. After some Googling, and some rooting around in my parts box, I came up with the Pololu DRV8825 Stepper Motor Driver part. This driver supports up to 32 micro-steps/step and is considerably smaller than the L298N – such a deal!

Pololu Micro-stepping Driver

At 32 microsteps/step, a full motor rev would take 200*32 = 6400 microsteps or 0.05625 deg/microstep . Now the above calculation would result in 10 deg/0.05625/10 = 177.777 –> 177 microsteps per scan step. This would result in step angles of 0, 177*0.05625 = 9.95802, 19.916, 29.874, 39.83, 49.79, and 59.748. So now we lose only the last 0.252 deg of scan – much nicer!

So, I put together a quick test, using an Arduino Uno, a spare NEMA 17 stepper motor, a Pololu DRV8825 from my parts box, and the Pololu Stepper library. Here’s the program:

/*
    Name:       PololuMicroStepperDemoV2.ino
    Created:	5/31/2020 11:05:30 PM
    Author:     FRANKNEWXPS15\Frank
*/

/*
 * Microstepping demo
 *
 * This requires that microstep control pins be connected in addition to STEP,DIR
 *
 * Copyright (C)2015 Laurentiu Badea
 *
 * This file may be redistributed under the terms of the MIT license.
 * A copy of this license has been included with this distribution in the file LICENSE.
 */
#include <Arduino.h>

 // Motor steps per revolution. Most steppers are 200 steps or 1.8 degrees/step
#define MOTOR_STEPS 200
//#define RPM 120
#define RPM 12

#define DIR 8
#define STEP 9
#define SLEEP 13 // optional (just delete SLEEP from everywhere if not used)

/*
 * Choose one of the sections below that match your board
 */

//#include "DRV8834.h"
//#define M0 10
//#define M1 11
//DRV8834 stepper(MOTOR_STEPS, DIR, STEP, SLEEP, M0, M1);

// #include "A4988.h"
// #define MS1 10
// #define MS2 11
// #define MS3 12
// A4988 stepper(MOTOR_STEPS, DIR, STEP, SLEEP, MS1, MS2, MS3);

 #include "DRV8825.h"
 #define MODE0 10
 #define MODE1 11
 #define MODE2 12
 DRV8825 stepper(MOTOR_STEPS, DIR, STEP, SLEEP, MODE0, MODE1, MODE2);

// #include "DRV8880.h"
// #define M0 10
// #define M1 11
// #define TRQ0 6
// #define TRQ1 7
// DRV8880 stepper(MOTOR_STEPS, DIR, STEP, SLEEP, M0, M1, TRQ0, TRQ1);

// #include "BasicStepperDriver.h" // generic
// BasicStepperDriver stepper(DIR, STEP);

void setup() {
    /*
     * Set target motor RPM.
     */
    stepper.begin(RPM);
    // if using enable/disable on ENABLE pin (active LOW) instead of SLEEP uncomment next line
    // stepper.setEnableActiveState(LOW);
    stepper.enable();

    // set current level (for DRV8880 only). 
    // Valid percent values are 25, 50, 75 or 100.
    // stepper.setCurrent(100);
}

void loop() {
    delay(1000);

    /*
     * Moving motor in full step mode is simple:
     */
    stepper.setMicrostep(1);  // Set microstep mode to 1:1

    // One complete revolution is 360°
    stepper.rotate(360);     // forward revolution
    stepper.rotate(-360);    // reverse revolution

    // One complete revolution is also MOTOR_STEPS steps in full step mode
    stepper.move(MOTOR_STEPS);    // forward revolution
    stepper.move(-MOTOR_STEPS);   // reverse revolution

    /*
     * Microstepping mode: 1, 2, 4, 8, 16 or 32 (where supported by driver)
     * Mode 1 is full speed.
     * Mode 32 is 32 microsteps per step.
     * The motor should rotate just as fast (at the set RPM),
     * but movement precision is increased, which may become visually apparent at lower RPMs.
     */
    stepper.setMicrostep(8);   // Set microstep mode to 1:8

    // In 1:8 microstepping mode, one revolution takes 8 times as many microsteps
    stepper.move(8 * MOTOR_STEPS);    // forward revolution
    stepper.move(-8 * MOTOR_STEPS);   // reverse revolution

    // One complete revolution is still 360° regardless of microstepping mode
    // rotate() is easier to use than move() when no need to land on precise microstep position
    stepper.rotate(360);
    stepper.rotate(-360);

    delay(5000);
}

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Name: PololuMicroStepperDemoV2.ino

Created: 5/31/2020 11:05:30 PM

Author: FRANKNEWXPS15\Frank

* Microstepping demo

* This requires that microstep control pins be connected in addition to STEP,DIR

* This file may be redistributed under the terms of the MIT license.

* A copy of this license has been included with this distribution in the file LICENSE.

#include <Arduino.h>

// Motor steps per revolution. Most steppers are 200 steps or 1.8 degrees/step

#define MOTOR_STEPS 200

//#define RPM 120

#define RPM 12

#define DIR 8

#define STEP 9

#define SLEEP 13 // optional (just delete SLEEP from everywhere if not used)

* Choose one of the sections below that match your board

//#include "DRV8834.h"

//#define M0 10

//#define M1 11

//DRV8834 stepper(MOTOR_STEPS, DIR, STEP, SLEEP, M0, M1);

// #include "A4988.h"

// #define MS1 10

// #define MS2 11

// #define MS3 12

// A4988 stepper(MOTOR_STEPS, DIR, STEP, SLEEP, MS1, MS2, MS3);

#include "DRV8825.h"

#define MODE0 10

#define MODE1 11

#define MODE2 12

DRV8825 stepper(MOTOR_STEPS, DIR, STEP, SLEEP, MODE0, MODE1, MODE2);

// #include "DRV8880.h"

// #define M0 10

// #define M1 11

// #define TRQ0 6

// #define TRQ1 7

// DRV8880 stepper(MOTOR_STEPS, DIR, STEP, SLEEP, M0, M1, TRQ0, TRQ1);

// #include "BasicStepperDriver.h" // generic

// BasicStepperDriver stepper(DIR, STEP);

void setup() {

* Set target motor RPM.

stepper.begin(RPM);

// if using enable/disable on ENABLE pin (active LOW) instead of SLEEP uncomment next line

// stepper.setEnableActiveState(LOW);

stepper.enable();

// set current level (for DRV8880 only).

// Valid percent values are 25, 50, 75 or 100.

// stepper.setCurrent(100);

}

void loop() {

delay(1000);

* Moving motor in full step mode is simple:

stepper.setMicrostep(1); // Set microstep mode to 1:1

// One complete revolution is 360°

stepper.rotate(360); // forward revolution

stepper.rotate(-360); // reverse revolution

// One complete revolution is also MOTOR_STEPS steps in full step mode

stepper.move(MOTOR_STEPS); // forward revolution

stepper.move(-MOTOR_STEPS); // reverse revolution

* Microstepping mode: 1, 2, 4, 8, 16 or 32 (where supported by driver)

* Mode 1 is full speed.

* Mode 32 is 32 microsteps per step.

* The motor should rotate just as fast (at the set RPM),

* but movement precision is increased, which may become visually apparent at lower RPMs.

stepper.setMicrostep(8); // Set microstep mode to 1:8

// In 1:8 microstepping mode, one revolution takes 8 times as many microsteps

stepper.move(8 * MOTOR_STEPS); // forward revolution

stepper.move(-8 * MOTOR_STEPS); // reverse revolution

// One complete revolution is still 360° regardless of microstepping mode

// rotate() is easier to use than move() when no need to land on precise microstep position

stepper.rotate(360);

stepper.rotate(-360);

delay(5000);

}

And the hardware test setup:

Pololu DRV8825 Microstep demo setup.

And a short video showing the stepper motor action. Note that close attention to the end of the red pointer wire shows the difference between ‘full-step’ and ‘micro-stepped’ behavior; the micro-stepped rotations are much smoother. Also, if you look very carefully, you can see the compass rose platform ‘counter-rotating’ in full-step mode, as the torque is high enough to rotate the stepper motor in the opposite direction to the shaft.

So now the idea is to incorporate micro-stepping capability into the Teensy NEMA 17 Rotary Table program, so that angle scans can be performed much more accurately than before.

02 June 2020 Update:

My original Pololu Microstep Demo program used an Arduino Uno to control the Pololu DRV8825 motor driver, but my Teensy Rotary Table setup obviously uses a Teensy and an L298N. To change the Rotary Table setup to utilize the DRV8825, I’ll need to make some adjustments to pin configurations.

The first step in the process was to change out the Arduino Uno for a Teensy (a Teensy 3.5 in this case) to verify that there were no problem with the Pololu microstep demo program running on a Teensy – done.

The next step was to change out the L298N driver on the rotary table setup with the Pololu DRV8825 driver, and modify the rotary table program to use the new driver with microstepping.

Here’s the new combined hardware layout, with both the rotary table and measurement sub-systems shown

Both measurement and rotary table sub-systems shown. Rotary table Teensy 3.2 at left foreground, followed by Teensy 3.5 measurement controller, the connection plugboard, and the triple VL53L0X sensors in the left background. The new DRV8825 is mounted on the center plugboard, and the NEMA 17 stepper motor with compass rose test platter at the right

Here’s the updated software using the Pololu DRV8825

/*
	Name:       Teensy_DRV8825_Rotary_Scan_Table.ino
	Created:	6/4/2020 12:59:57 AM
	Author:     FRANKNEWXPS15\Frank
*/

/*
Teensy DRV8825 Rotary Table Program

This program controls a NEMA 17 stepper motor using a Pololu DRV8825 motor driver. It
Takes user input to define the boresight (zero) position and the start and stop angles
in degrees relative to the zero position.  Then it moves to the start position and waits
for a HIGH level on SCAN_START_PIN.  After this signal is received, the motor is
stepped through to the stop position. At the stop position, the SCAN_COMPLETE_PIN is
driven HIGH.

The Stepper motor is connected to a DRV8825 motor driver with one coil on A1/A2, and the
other coil on B1/B2.  It may turn out that one coil's leads have to be reversed to match
the motor rotation direction with the program direction.

The NEMA 17 motor is assumed to execute 200 steps/revolution.  Change the StepsPerRevolution
constant for other values.

05/27/20:  Performs an angular scan over user-supplied range of angles. By default a complete scan
from start position to stop position is performed, followed by a return to the start position
However, if the STEP_ENABLE_PIN (held HIGH by default) is pulled LOW, the program will wait
until it goes HIGH before performing the next step.  In this case, a scan iteration would go
as follows

	Step 1 - Scan parameters entered, motor moves to start position, waits for LOW on SCAN_START_PIN
	Step 2 - Measurement program pulls SCAN_START_PIN LOW for 1 sec, then back HIGH
	Step 3 - Measurement program takes a measurement & retrieves step# & angle value via I2C request
	Step 4 - Measurement program pulls SCAN_STEP_ENABLE_PIN LOW
	Step 5 - Motor moves to first/next step, and outputs HIGH on SCAN_STEP_COMPLETE_PIN
	Step 6 - Measurement program waits for HIGH on SCAN_STEP_COMPLETE_PIN
	Step 7 - Measurement program takes a measurement & retrieves step# & angle value via I2C request
	Step 8 - Repeat Steps 4-7 until scan complete
	Step 9 - SCAN_COMPLETE_PIN goes HIGH
*/

//O5/30/20 Added I2C connection to pass step# & relative angle values to measurement program
//05/02/20 Rev to use Pololu DRV8825 & micro-stepping

#include <Wire.h>
#include "I2C_Anything.h"
#include "DRV8825.h"

const int SLAVE_ADDR = 8; //added 05/30/20

#pragma region MOTOR_CONSTANTS
 // Motor steps per revolution. Most steppers are 200 steps or 1.8 degrees/step
//06/02/20 now using Pololu DRV8825
const int MOTOR_STEPS_PER_REV = 200;
const int MICROSTEPS_PER_STEP = 32;
const int MICROSTEPS_PER_REV = MICROSTEPS_PER_STEP * MOTOR_STEPS_PER_REV;
const int DEG_PER_MICROSTEP = 360 / MICROSTEPS_PER_REV;
const int MICROSTEPS_PER_DEG = MICROSTEPS_PER_REV / 360;
const int DEFAULT_RPM = 12;
const int POSITIONING_SPEED_RPM = 100;
const int DEFAULT_MOTOR_STEPS_TO_MOVE = 10;
#pragma endregion Motor Constants

#pragma region PIN_ASSIGNMENTS
const int DIR = 8;
const int STEP = 9;
const int SLEEP = 13; // optional (just delete SLEEP from everywhere if not used)

const int MODE0 = 10;
const int MODE1 = 11;
const int MODE2 = 12;

const int SCAN_START_PIN = 2;
const int SCAN_STEP_ENABLE_PIN = 3;
const int SCAN_STEP_COMPLETE_PIN = 4;
const int SCAN_COMPLETE_PIN = 5;
#pragma endregion Pin Assignments

DRV8825 stepper(MOTOR_STEPS_PER_REV, DIR, STEP, SLEEP, MODE0, MODE1, MODE2);

char Instr[20];

//DRV8825
int zeroPos;
int scanStartDeg;
int scanStartMicroSteps; //scanStartDeg converted to steps
int scanStopDeg;
int scanStopSteps; //scanStopDeg converted to steps
int scanNumberofSteps; //added 05/27/20
int stepsToMove; //steps to move to initial position
int curMotorStepVal; //keeps track of current position, in steps
float curRelPointingAngleDeg; //keeps track of current relative pointing angle, in degrees
int curAngleStepVal; //keeps track of current table step iteration value
bool bStopPosDone = false;
int scanSpeedRpm = 6;



void setup()
{
	//added 05/30/20 to provide step# & angle values to Angle Scan program
	Wire.begin(SLAVE_ADDR);
	Wire.setSCL(18);
	Wire.setSCL(19);
	Wire.setClock(100000);
	Wire.onRequest(requestEvent);

	//06/02/20 now using Pololu DRV8825 microstepping motor driver
	stepper.begin(DEFAULT_RPM);
	// if using enable/disable on ENABLE pin (active LOW) instead of SLEEP uncomment next line
	// stepper.setEnableActiveState(LOW);
	stepper.enable();

	/*
	 * Microstepping mode: 1, 2, 4, 8, 16 or 32 (where supported by driver)
	 * Mode 1 is full speed.
	 * Mode 32 is 32 microsteps per step.
	 * The motor should rotate just as fast (at the set RPM),
	 * but movement precision is increased, which may become visually apparent at lower RPMs.
	 */
	stepper.setMicrostep(MICROSTEPS_PER_STEP);   // Set microstep mode to 1:32



	Serial.begin(115200);
	unsigned long now = millis();
	while (!Serial)
	{
		delay(10);
	}

	delay(5000); //05/28/20 delay AFTER Serial object instantiation is NECESSARY!

	Serial.print("Serial available after "); Serial.print(millis() - now); Serial.print(" millisec");

	pinMode(SCAN_START_PIN, INPUT_PULLUP);
	pinMode(SCAN_STEP_ENABLE_PIN, INPUT_PULLUP);
	pinMode(SCAN_STEP_COMPLETE_PIN, OUTPUT);
	pinMode(SCAN_COMPLETE_PIN, OUTPUT);

	//init SCAN_COMPLETE_PIN, SCAN_STEP_COMPLETE to LOW (not complete) state
	digitalWrite(SCAN_COMPLETE_PIN, LOW);
	digitalWrite(SCAN_STEP_COMPLETE_PIN, LOW);

	//added 05/26/20
	Serial.printf("Serial.printf: NEMA-17 Stepper Rotary Table Program\n");

	//get motor speed to be used
	scanSpeedRpm = GetIntegerParameter("Motor speed RPM", 6);


	//set zero position
	Serial.println("Set stepper zero position.  Enter +steps for CW, -steps for CCW, Q to exit");
	while (!bStopPosDone)
	{
		while (Serial.available() == 0); //waits for input
		if (toascii(Serial.peek()) == 'Q' || toascii(Serial.peek()) == 'q')
		{
			bStopPosDone = true;
			curMotorStepVal = 0;
		}
		else
		{
			stepsToMove = GetIntegerParameter("Steps to move (- = CCW, + = CW)?", DEFAULT_MOTOR_STEPS_TO_MOVE);
			Serial.print("Steps to move = "); Serial.println(stepsToMove);
			stepper.setRPM(POSITIONING_SPEED_RPM);
			stepper.move(stepsToMove);
		}
	}

	Serial.readString(); //clear the input buffer - could still have chars in it
	Serial.print("curMotorStepVal = "); Serial.println(curMotorStepVal);

	//set scan start/stop positions in degrees
	scanStartDeg = GetIntegerParameter("Scan Start Pos in Degrees Relative to Zero", -90);
	scanStopDeg = GetIntegerParameter("Scan Stop Pos in Degrees Relative to Zero", 90);
	scanNumberofSteps = GetIntegerParameter("Number of Steps", 18);
	curRelPointingAngleDeg = scanStartDeg; //added 05/30/20

	Serial.println("Run Parameters:");
	Serial.print("Speed: "); Serial.print(scanSpeedRpm); Serial.println(" RPM");
	Serial.print("Scan Start: "); Serial.print(scanStartDeg); Serial.println(" Deg");
	Serial.print("Scan Stop: "); Serial.print(scanStopDeg); Serial.println(" Deg");
	Serial.print("Scan Steps: "); Serial.println(scanNumberofSteps);

	//06/02/20 Now using Pololu DRV8825 driver & microstepping
	int scandeg = abs(scanStopDeg - scanStartDeg);
	double scanstepdeg = scandeg / scanNumberofSteps;

	//go to scan start pos
	stepper.setRPM(POSITIONING_SPEED_RPM);
	stepper.rotate(scanStartDeg);

	while (1)  //user has opportunity to exit after each scan
	{
		//wait for trigger
		Serial.printf("waiting for LOW on SCAN_START_PIN (pin %d) ...\n", SCAN_START_PIN);
		while (digitalRead(SCAN_START_PIN) == HIGH)
		{
			delay(100);
		}

		Serial.println("Scan Triggered - starting scan, setting SCAN_COMPLETE_PIN to LOW\n");
		digitalWrite(SCAN_COMPLETE_PIN, LOW);

		stepper.setRPM(scanSpeedRpm);

		for (curAngleStepVal = 1; curAngleStepVal <= scanNumberofSteps; curAngleStepVal++)
		{
			curRelPointingAngleDeg = scanStartDeg + (curAngleStepVal)*scanstepdeg;

			//when SCAN_STEP_ENABLE_PIN goes LOW, go to first/next step.
			while (digitalRead(SCAN_STEP_ENABLE_PIN))
			{

			}

			unsigned long now = millis();
			digitalWrite(SCAN_STEP_COMPLETE_PIN, LOW);
			Serial.printf("Scan Step %d Triggered: moving to %3.2f deg\n", curAngleStepVal, curRelPointingAngleDeg);

			//DRV8825
			stepper.rotate(scanstepdeg); //rotate to next scan angle

			//output HIGH on SCAN_STEP_COMPLETE_PIN
//DEBUG!!
			//Serial.printf("Outputting HIGH on SCAN_STEP_COMPLETE_PIN\n");
			//Serial.printf("Done in %lu Msec - Current Angle = %3.2f\n", millis() - now, curRelPointingAngleDeg);
//DEBUG!!

			digitalWrite(SCAN_STEP_COMPLETE_PIN, HIGH);
			//delay(50);  //make the HIGH period visible on scope
		}

		//quit
		Serial.printf("Outputting HIGH on SCAN_COMPLETE_PIN (pin %d)\n", SCAN_COMPLETE_PIN);

		digitalWrite(SCAN_COMPLETE_PIN, HIGH);

		//return to start position
		//DRV8825
		stepper.setRPM(POSITIONING_SPEED_RPM);
		stepper.rotate(-scandeg);

		//re-initialize step counter and current pointing angle
		curAngleStepVal = 0;
		curRelPointingAngleDeg = scanStartDeg;

		Serial.printf("Enter any key to continue\n");
		while (!Serial.available())
		{

		}

		//consume bytes until Serial buffer is empty to avoid unintended triggers
		int incomingByte;
		while (Serial.available())
		{
			incomingByte = Serial.read();
			Serial.printf("Consuming 0x%x\n", incomingByte);
		}

	}
}


void loop()
{
}

int GetIntegerParameter(String prompt, int defaultval)
{
	int param = 0;
	bool bDone = false;

	while (!bDone)
	{
		Serial.print(prompt); Serial.print(" ("); Serial.print(defaultval); Serial.print("): ");
		while (Serial.available() == 0); //waits for input
										 //String res = Serial.readString().trim();
		String res = Serial.readString();
		res.trim();

		int reslen = res.length();
		if (reslen == 0) //user entered CR only
		{
			bDone = true;
			param = defaultval;
		}
		else
		{
			res.toCharArray(Instr, reslen + 1);
			//if (isNumeric(Instr) && atoi(Instr) >= 0)
			if (isNumeric(Instr))
			{
				param = atoi(Instr);
				bDone = true;
			}
			else
			{
				Serial.print(Instr); Serial.println(" Is invalid input - please try again");
			}
		}
	}
	Serial.println(param);
	return param;
}

// check a string to see if it is numeric and accept Decimal point
//copied from defragster's post at https://forum.pjrc.com/threads/27842-testing-if-a-string-is-numeric
bool isNumeric(char* str)
{
	byte ii = 0;
	bool RetVal = false;
	if ('-' == str[ii])
		ii++;
	while (str[ii])
	{
		if ('.' == str[ii]) {
			ii++;
			break;
		}
		if (!isdigit(str[ii])) return false;
		ii++;
		RetVal = true;
	}
	while (str[ii])
	{
		if (!isdigit(str[ii])) return false;
		ii++;
		RetVal = true;
	}
	return RetVal;
}

//05/30/20 added to report current angle step# & relative pointing angle to measurement program
void requestEvent()
{
	//send the current step# and current relative pointing angle
//DEBUG!!
	//Serial.printf("In requestEvent: curAngleStep = %d, curRelAngle = %2.2f\n", 
	//	curAngleStepVal, curAngleStepVal, curRelPointingAngleDeg, curRelPointingAngleDeg);
//DEBUG!!

	I2C_writeAnything(curAngleStepVal);
	I2C_writeAnything(curRelPointingAngleDeg);
}

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Name: Teensy_DRV8825_Rotary_Scan_Table.ino

Created: 6/4/2020 12:59:57 AM

Author: FRANKNEWXPS15\Frank

Teensy DRV8825 Rotary Table Program

This program controls a NEMA 17 stepper motor using a Pololu DRV8825 motor driver. It

Takes user input to define the boresight (zero) position and the start and stop angles

in degrees relative to the zero position. Then it moves to the start position and waits

for a HIGH level on SCAN_START_PIN. After this signal is received, the motor is

stepped through to the stop position. At the stop position, the SCAN_COMPLETE_PIN is

driven HIGH.

The Stepper motor is connected to a DRV8825 motor driver with one coil on A1/A2, and the

other coil on B1/B2. It may turn out that one coil's leads have to be reversed to match

the motor rotation direction with the program direction.

The NEMA 17 motor is assumed to execute 200 steps/revolution. Change the StepsPerRevolution

constant for other values.

05/27/20: Performs an angular scan over user-supplied range of angles. By default a complete scan

from start position to stop position is performed, followed by a return to the start position

However, if the STEP_ENABLE_PIN (held HIGH by default) is pulled LOW, the program will wait

until it goes HIGH before performing the next step. In this case, a scan iteration would go

as follows

Step 1 - Scan parameters entered, motor moves to start position, waits for LOW on SCAN_START_PIN

Step 2 - Measurement program pulls SCAN_START_PIN LOW for 1 sec, then back HIGH

Step 3 - Measurement program takes a measurement & retrieves step# & angle value via I2C request

Step 4 - Measurement program pulls SCAN_STEP_ENABLE_PIN LOW

Step 5 - Motor moves to first/next step, and outputs HIGH on SCAN_STEP_COMPLETE_PIN

Step 6 - Measurement program waits for HIGH on SCAN_STEP_COMPLETE_PIN

Step 7 - Measurement program takes a measurement & retrieves step# & angle value via I2C request

Step 8 - Repeat Steps 4-7 until scan complete

Step 9 - SCAN_COMPLETE_PIN goes HIGH

//O5/30/20 Added I2C connection to pass step# & relative angle values to measurement program

//05/02/20 Rev to use Pololu DRV8825 & micro-stepping

#include <Wire.h>

#include "I2C_Anything.h"

#include "DRV8825.h"

const int SLAVE_ADDR = 8; //added 05/30/20

#pragma region MOTOR_CONSTANTS

// Motor steps per revolution. Most steppers are 200 steps or 1.8 degrees/step

//06/02/20 now using Pololu DRV8825

const int MOTOR_STEPS_PER_REV = 200;

const int MICROSTEPS_PER_STEP = 32;

const int MICROSTEPS_PER_REV = MICROSTEPS_PER_STEP * MOTOR_STEPS_PER_REV;

const int DEG_PER_MICROSTEP = 360 / MICROSTEPS_PER_REV;

const int MICROSTEPS_PER_DEG = MICROSTEPS_PER_REV / 360;

const int DEFAULT_RPM = 12;

const int POSITIONING_SPEED_RPM = 100;

const int DEFAULT_MOTOR_STEPS_TO_MOVE = 10;

#pragma endregion Motor Constants

#pragma region PIN_ASSIGNMENTS

const int DIR = 8;

const int STEP = 9;

const int SLEEP = 13; // optional (just delete SLEEP from everywhere if not used)

const int MODE0 = 10;

const int MODE1 = 11;

const int MODE2 = 12;

const int SCAN_START_PIN = 2;

const int SCAN_STEP_ENABLE_PIN = 3;

const int SCAN_STEP_COMPLETE_PIN = 4;

const int SCAN_COMPLETE_PIN = 5;

#pragma endregion Pin Assignments

DRV8825 stepper(MOTOR_STEPS_PER_REV, DIR, STEP, SLEEP, MODE0, MODE1, MODE2);

char Instr[20];

//DRV8825

int zeroPos;

int scanStartDeg;

int scanStartMicroSteps; //scanStartDeg converted to steps

int scanStopDeg;

int scanStopSteps; //scanStopDeg converted to steps

int scanNumberofSteps; //added 05/27/20

int stepsToMove; //steps to move to initial position

int curMotorStepVal; //keeps track of current position, in steps

float curRelPointingAngleDeg; //keeps track of current relative pointing angle, in degrees

int curAngleStepVal; //keeps track of current table step iteration value

bool bStopPosDone = false;

int scanSpeedRpm = 6;

void setup()

{

//added 05/30/20 to provide step# & angle values to Angle Scan program

Wire.begin(SLAVE_ADDR);

Wire.setSCL(18);

Wire.setSCL(19);

Wire.setClock(100000);

Wire.onRequest(requestEvent);

//06/02/20 now using Pololu DRV8825 microstepping motor driver

stepper.begin(DEFAULT_RPM);

// if using enable/disable on ENABLE pin (active LOW) instead of SLEEP uncomment next line

// stepper.setEnableActiveState(LOW);

stepper.enable();

* Microstepping mode: 1, 2, 4, 8, 16 or 32 (where supported by driver)

* Mode 1 is full speed.

* Mode 32 is 32 microsteps per step.

* The motor should rotate just as fast (at the set RPM),

* but movement precision is increased, which may become visually apparent at lower RPMs.

stepper.setMicrostep(MICROSTEPS_PER_STEP); // Set microstep mode to 1:32

Serial.begin(115200);

unsigned long now = millis();

while (!Serial)

{

delay(10);

}

delay(5000); //05/28/20 delay AFTER Serial object instantiation is NECESSARY!

Serial.print("Serial available after "); Serial.print(millis() - now); Serial.print(" millisec");

pinMode(SCAN_START_PIN, INPUT_PULLUP);

pinMode(SCAN_STEP_ENABLE_PIN, INPUT_PULLUP);

pinMode(SCAN_STEP_COMPLETE_PIN, OUTPUT);

pinMode(SCAN_COMPLETE_PIN, OUTPUT);

//init SCAN_COMPLETE_PIN, SCAN_STEP_COMPLETE to LOW (not complete) state

digitalWrite(SCAN_COMPLETE_PIN, LOW);

digitalWrite(SCAN_STEP_COMPLETE_PIN, LOW);

//added 05/26/20

Serial.printf("Serial.printf: NEMA-17 Stepper Rotary Table Program\n");

//get motor speed to be used

scanSpeedRpm = GetIntegerParameter("Motor speed RPM", 6);

//set zero position

Serial.println("Set stepper zero position. Enter +steps for CW, -steps for CCW, Q to exit");

while (!bStopPosDone)

{

while (Serial.available() == 0); //waits for input

if (toascii(Serial.peek()) == 'Q' || toascii(Serial.peek()) == 'q')

{

bStopPosDone = true;

curMotorStepVal = 0;

}

else

{

stepsToMove = GetIntegerParameter("Steps to move (- = CCW, + = CW)?", DEFAULT_MOTOR_STEPS_TO_MOVE);

Serial.print("Steps to move = "); Serial.println(stepsToMove);

stepper.setRPM(POSITIONING_SPEED_RPM);

stepper.move(stepsToMove);

}

Serial.readString(); //clear the input buffer - could still have chars in it

Serial.print("curMotorStepVal = "); Serial.println(curMotorStepVal);

//set scan start/stop positions in degrees

scanStartDeg = GetIntegerParameter("Scan Start Pos in Degrees Relative to Zero", -90);

scanStopDeg = GetIntegerParameter("Scan Stop Pos in Degrees Relative to Zero", 90);

scanNumberofSteps = GetIntegerParameter("Number of Steps", 18);

curRelPointingAngleDeg = scanStartDeg; //added 05/30/20

Serial.println("Run Parameters:");

Serial.print("Speed: "); Serial.print(scanSpeedRpm); Serial.println(" RPM");

Serial.print("Scan Start: "); Serial.print(scanStartDeg); Serial.println(" Deg");

Serial.print("Scan Stop: "); Serial.print(scanStopDeg); Serial.println(" Deg");

Serial.print("Scan Steps: "); Serial.println(scanNumberofSteps);

//06/02/20 Now using Pololu DRV8825 driver & microstepping

int scandeg = abs(scanStopDeg - scanStartDeg);

double scanstepdeg = scandeg / scanNumberofSteps;

//go to scan start pos

stepper.setRPM(POSITIONING_SPEED_RPM);

stepper.rotate(scanStartDeg);

while (1) //user has opportunity to exit after each scan

{

//wait for trigger

Serial.printf("waiting for LOW on SCAN_START_PIN (pin %d) ...\n", SCAN_START_PIN);

while (digitalRead(SCAN_START_PIN) == HIGH)

{

delay(100);

}

Serial.println("Scan Triggered - starting scan, setting SCAN_COMPLETE_PIN to LOW\n");

digitalWrite(SCAN_COMPLETE_PIN, LOW);

stepper.setRPM(scanSpeedRpm);

for (curAngleStepVal = 1; curAngleStepVal <= scanNumberofSteps; curAngleStepVal++)

{

curRelPointingAngleDeg = scanStartDeg + (curAngleStepVal)*scanstepdeg;

//when SCAN_STEP_ENABLE_PIN goes LOW, go to first/next step.

while (digitalRead(SCAN_STEP_ENABLE_PIN))

{

}

unsigned long now = millis();

digitalWrite(SCAN_STEP_COMPLETE_PIN, LOW);

Serial.printf("Scan Step %d Triggered: moving to %3.2f deg\n", curAngleStepVal, curRelPointingAngleDeg);

//DRV8825

stepper.rotate(scanstepdeg); //rotate to next scan angle

//output HIGH on SCAN_STEP_COMPLETE_PIN

//DEBUG!!

//Serial.printf("Outputting HIGH on SCAN_STEP_COMPLETE_PIN\n");

//Serial.printf("Done in %lu Msec - Current Angle = %3.2f\n", millis() - now, curRelPointingAngleDeg);

//DEBUG!!

digitalWrite(SCAN_STEP_COMPLETE_PIN, HIGH);

//delay(50); //make the HIGH period visible on scope

}

//quit

Serial.printf("Outputting HIGH on SCAN_COMPLETE_PIN (pin %d)\n", SCAN_COMPLETE_PIN);

digitalWrite(SCAN_COMPLETE_PIN, HIGH);

//return to start position

//DRV8825

stepper.setRPM(POSITIONING_SPEED_RPM);

stepper.rotate(-scandeg);

//re-initialize step counter and current pointing angle

curAngleStepVal = 0;

curRelPointingAngleDeg = scanStartDeg;

Serial.printf("Enter any key to continue\n");

while (!Serial.available())

{

}

//consume bytes until Serial buffer is empty to avoid unintended triggers

int incomingByte;

while (Serial.available())

{

incomingByte = Serial.read();

Serial.printf("Consuming 0x%x\n", incomingByte);

}

void loop()

{

}

int GetIntegerParameter(String prompt, int defaultval)

{

int param = 0;

bool bDone = false;

while (!bDone)

{

Serial.print(prompt); Serial.print(" ("); Serial.print(defaultval); Serial.print("): ");

while (Serial.available() == 0); //waits for input

//String res = Serial.readString().trim();

String res = Serial.readString();

res.trim();

int reslen = res.length();

if (reslen == 0) //user entered CR only

{

bDone = true;

param = defaultval;

}

else

{

res.toCharArray(Instr, reslen + 1);

//if (isNumeric(Instr) && atoi(Instr) >= 0)

if (isNumeric(Instr))

{

param = atoi(Instr);

bDone = true;

}

else

{

Serial.print(Instr); Serial.println(" Is invalid input - please try again");

}

Serial.println(param);

return param;

}

// check a string to see if it is numeric and accept Decimal point

//copied from defragster's post at https://forum.pjrc.com/threads/27842-testing-if-a-string-is-numeric

bool isNumeric(char* str)

{

byte ii = 0;

bool RetVal = false;

if ('-' == str[ii])

ii++;

while (str[ii])

{

if ('.' == str[ii]) {

ii++;

break;

}

if (!isdigit(str[ii])) return false;

ii++;

RetVal = true;

}

while (str[ii])

{

if (!isdigit(str[ii])) return false;

ii++;

RetVal = true;

}

return RetVal;

}

//05/30/20 added to report current angle step# & relative pointing angle to measurement program

void requestEvent()

{

//send the current step# and current relative pointing angle

//DEBUG!!

//Serial.printf("In requestEvent: curAngleStep = %d, curRelAngle = %2.2f\n",

// curAngleStepVal, curAngleStepVal, curRelPointingAngleDeg, curRelPointingAngleDeg);

//DEBUG!!

I2C_writeAnything(curAngleStepVal);

I2C_writeAnything(curRelPointingAngleDeg);

}

And the updated hardware schematic:

Here’s the output from a typical 180-degree scan

The triple VL53L0X scanner program:

Starting Angle Scan...
 
Msec	Step#	RelDeg	Front	Center	Rear	Steer
23815846	0	-90.00	121	30	17	3.47
23816965	1	-80.00	120	28	19	3.61
23817408	2	-70.00	118	29	18	3.45
23817852	3	-60.00	120	30	20	3.33
23818296	4	-50.00	123	32	19	3.25
23818740	5	-40.00	120	28	20	3.57
23819183	6	-30.00	122	30	19	3.43
23819627	7	-20.00	119	29	22	3.34
23820071	8	-10.00	122	29	19	3.55
23820515	9	0.00	121	31	20	3.26
23820958	10	10.00	122	31	17	3.39
23821402	11	20.00	120	30	16	3.47
23821846	12	30.00	120	27	22	3.63
23822290	13	40.00	120	31	20	3.23
23822733	14	50.00	124	29	19	3.62
23823177	15	60.00	120	30	19	3.37
23823621	16	70.00	123	29	23	3.45
23824065	17	80.00	120	31	18	3.29
23824508	18	90.00	116	31	20	3.10
SCAN_COMPLETE_PIN HIGH Received - Scan is Complete!
Enter Q to quit, anything else for another scan

Starting Angle Scan...

Msec Step# RelDeg Front Center Rear Steer

23815846 0 -90.00 121 30 17 3.47

23816965 1 -80.00 120 28 19 3.61

23817408 2 -70.00 118 29 18 3.45

23817852 3 -60.00 120 30 20 3.33

23818296 4 -50.00 123 32 19 3.25

23818740 5 -40.00 120 28 20 3.57

23819183 6 -30.00 122 30 19 3.43

23819627 7 -20.00 119 29 22 3.34

23820071 8 -10.00 122 29 19 3.55

23820515 9 0.00 121 31 20 3.26

23820958 10 10.00 122 31 17 3.39

23821402 11 20.00 120 30 16 3.47

23821846 12 30.00 120 27 22 3.63

23822290 13 40.00 120 31 20 3.23

23822733 14 50.00 124 29 19 3.62

23823177 15 60.00 120 30 19 3.37

23823621 16 70.00 123 29 23 3.45

23824065 17 80.00 120 31 18 3.29

23824508 18 90.00 116 31 20 3.10

SCAN_COMPLETE_PIN HIGH Received - Scan is Complete!

Enter Q to quit, anything else for another scan

The DRV8825 Rotary Table program:

waiting for LOW on SCAN_START_PIN (pin 2) ...
Scan Triggered - starting scan, setting SCAN_COMPLETE_PIN to LOW

Scan Step 1 Triggered: moving to -80.00 deg
Scan Step 2 Triggered: moving to -70.00 deg
Scan Step 3 Triggered: moving to -60.00 deg
Scan Step 4 Triggered: moving to -50.00 deg
Scan Step 5 Triggered: moving to -40.00 deg
Scan Step 6 Triggered: moving to -30.00 deg
Scan Step 7 Triggered: moving to -20.00 deg
Scan Step 8 Triggered: moving to -10.00 deg
Scan Step 9 Triggered: moving to 0.00 deg
Scan Step 10 Triggered: moving to 10.00 deg
Scan Step 11 Triggered: moving to 20.00 deg
Scan Step 12 Triggered: moving to 30.00 deg
Scan Step 13 Triggered: moving to 40.00 deg
Scan Step 14 Triggered: moving to 50.00 deg
Scan Step 15 Triggered: moving to 60.00 deg
Scan Step 16 Triggered: moving to 70.00 deg
Scan Step 17 Triggered: moving to 80.00 deg
Scan Step 18 Triggered: moving to 90.00 deg
Outputting HIGH on SCAN_COMPLETE_PIN (pin 5)
Enter any key to continue

waiting for LOW on SCAN_START_PIN (pin 2) ...

Scan Triggered - starting scan, setting SCAN_COMPLETE_PIN to LOW

Scan Step 1 Triggered: moving to -80.00 deg

Scan Step 2 Triggered: moving to -70.00 deg

Scan Step 3 Triggered: moving to -60.00 deg

Scan Step 4 Triggered: moving to -50.00 deg

Scan Step 5 Triggered: moving to -40.00 deg

Scan Step 6 Triggered: moving to -30.00 deg

Scan Step 7 Triggered: moving to -20.00 deg

Scan Step 8 Triggered: moving to -10.00 deg

Scan Step 9 Triggered: moving to 0.00 deg

Scan Step 10 Triggered: moving to 10.00 deg

Scan Step 11 Triggered: moving to 20.00 deg

Scan Step 12 Triggered: moving to 30.00 deg

Scan Step 13 Triggered: moving to 40.00 deg

Scan Step 14 Triggered: moving to 50.00 deg

Scan Step 15 Triggered: moving to 60.00 deg

Scan Step 16 Triggered: moving to 70.00 deg

Scan Step 17 Triggered: moving to 80.00 deg

Scan Step 18 Triggered: moving to 90.00 deg

Outputting HIGH on SCAN_COMPLETE_PIN (pin 5)

Enter any key to continue

For anyone interested in using this program, it is available on my GitHub site at https://github.com/paynterf/Teensy-DRV8825-Rotary-Scan-Table

Paynter's Palace

Monthly Archives: May 2020

Teensy NEMA 17 Stepper Motor Rotary Scanner Program

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Upgrade to Micro-step capable motor driver:

02 June 2020 Update:

Off-perpendicular measurement problems with HC-SRO4 Ping Measurements

18 May 2020 Update:

19 May Update: