Serial Communication to Control Stepper

Question

**I wanted to add an updated code after I have finished it to help others in the future if they are ever looking for it.

EDIT AT END OF QUESTION AFTER ANSWER AND CODE UPDATE.**

I currently have an Uno with a CNCBoard Hat.

I am running a program on my RPi and sending a value through serial to the Arduino. I am receiving what I believe is a string, converting it to an int using toInt() (I found this solution somewhere). I then want to write that value to the stepper I have connected.

I know the stepper works, because if I run a simple test program such as this one:

const int stepX = 2;
const int dirX  = 5;

const int stepY = 3;
const int dirY  = 6;

const int stepZ = 4;
const int dirZ  = 7;

const int enPin = 8;

void setup() {
  // Sets the two pins as Outputs
  pinMode(stepX, OUTPUT);
  pinMode(dirX, OUTPUT);
  pinMode(enPin, OUTPUT);

  digitalWrite(enPin, LOW);
  digitalWrite(dirX, HIGH);
  digitalWrite(dirY, LOW);
  digitalWrite(dirZ, HIGH);
}

void loop() {
  // Enables the motor to move in a particular direction
  // Makes 200 pulses for making one full cycle rotation
  for (int x = 0; x < 200; x++) {
    digitalWrite(stepX,HIGH);
    delayMicroseconds(1000);
    digitalWrite(stepX, LOW);
    delayMicroseconds(1000);
  }
   delay(1000); // One second delay
}

The stepper rotates as the program describes. Where 200 is the pulse count.

The program I am currently trying to use is:

// defines pins numbers
//Front left wheel
const int stepX = 2;
const int dirX  = 5;

//Front right wheel
const int stepY = 3;
const int dirY  = 6;

//Back left wheel
const int stepZ = 4;
const int dirZ  = 7;

//Back right wheel
const int stepA = 12;
const int dirA  = 13;

const int enPin = 8;

void setup() {
  Serial.begin(9600);

  // Sets the two pins as Outputs
  pinMode(stepX, OUTPUT);
  pinMode(dirX, OUTPUT);

  pinMode(stepY, OUTPUT);
  pinMode(dirY, OUTPUT);

  pinMode(stepZ, OUTPUT);
  pinMode(dirZ, OUTPUT);

  pinMode(enPin, OUTPUT);

  digitalWrite(enPin, LOW);
  digitalWrite(dirX, HIGH);
  digitalWrite(dirY, LOW);
  digitalWrite(dirZ, HIGH);
  digitalWrite(dirA, HIGH);
}

void loop() {
  String YpulseEncode;
  if (Serial.available() > 0) {          
    YpulseEncode = Serial.readStringUntil('\n');
    int yMove1 = YpulseEncode.toInt();
    //XpulseCalc = Serial.read();

    //Serial.print("YpulseCalc: ");
    Serial.println(yMove1 * (-1));
    //Serial.print("YpulseCalc +: ");
    //Serial.println(YpulseCalc
    //Serial.print("XpulseCalc: ");
    //Serial.println(XpulseCalc);
    delay(5000);
    Serial.end();
    if (yMove1 != 0) {
      // Enables the motor to move in a particular direction
      // Makes 200 pulses for making one full cycle rotation
      for (int x = 0; x < (yMove1); x++) {
        digitalWrite(stepX, HIGH);
        delayMicroseconds(1000);
        digitalWrite(stepX, LOW);
      }
    }
  }
}

The number I am receiving from the RPi is -267. So when the serial monitor shows it, it is 267. I want to send the number 267 pulses to the stepper motor.

EDIT - UPDATED CODE

AccelStepper yStepper(AccelStepper::DRIVER, 2, 5);

// defines pins numbers
//Front left wheel
const int stepX = 2;
const int dirX  = 5;

//Front right wheel
const int stepY = 3;
const int dirY  = 6;

//Back left wheel
const int stepZ = 4;
const int dirZ  = 7;

//Back right wheel
const int stepA = 12;
const int dirA  = 13;

const int enPin = 8;

void setup() {
  yStepper.setMaxSpeed(800);
  yStepper.setAcceleration(400);
  
  
  Serial.begin(9600);

  // Sets the pins as Outputs
  pinMode(stepX, OUTPUT);
  pinMode(dirX, OUTPUT);

  pinMode(stepY, OUTPUT);
  pinMode(dirY, OUTPUT);

  pinMode(stepZ, OUTPUT);
  pinMode(dirZ, OUTPUT);

  pinMode(enPin, OUTPUT);

  digitalWrite(enPin, LOW);
  digitalWrite(dirX, HIGH);
  digitalWrite(dirY, LOW);
  digitalWrite(dirZ, HIGH);
  digitalWrite(dirA, HIGH);
}

void loop() {

  String YpulseEncode;
  if (Serial.available() > 0) {          
    YpulseEncode = Serial.readStringUntil('\n');
    int yMove1 = YpulseEncode.toInt();
    
if (yMove1 < 0) {
    int yMoveNew = yMove1 * (-1);

    //XpulseCalc = Serial.read();
    //Serial.print("YpulseCalc: ");
    Serial.println(yMove1 * (-1));
    //Serial.print("YpulseCalc +: ");
    //Serial.println(YpulseCalc
    //Serial.print("XpulseCalc: ");
    //Serial.println(XpulseCalc);
    delay(2000);

      // Enables the motor to move in a particular direction
      // Makes 200 pulses for making one full cycle rotation
      //for (int x = 0; x < yMoveNew; x++) {
      yStepper.move(yMoveNew);
      yStepper.runToPosition();
        //digitalWrite(stepX, HIGH);
        delayMicroseconds(1000);
        //digitalWrite(stepX, LOW);
      //}
    }
  }
}

Answer 1

You have 2 problems, which are already mentioned in the comments:

• You call Serial.end() after you received one line. That will stop the Serial hardware. Thus the code will only receive one line and then ignore any data from Serial. I don't think, that you want this. So just remove the Serial.end().

• yMove1 is negative, while your for loop has the condition int x = 0; x < (yMove1); x++. But zero is always higher than a negative number. Thus the for does not run at all (the condition x < yMove1 is false, when yMove1 is negative). I don't quite understand, why you want to provide a negative number. You don't have any code for direction reversing. In the current state I would suggest just not sending a negative number. I cannot say more, because it is unclear, what exactly you want here.

---

Note:

• The parentheses around yMove1 inside the for loop condition is not needed.
• The if statement if (yMove1 != 0) is not needed. If yMove1 is zero, the for loop will just not run, because it starts with zero.