Python to Raspberry Pi to Arduino to Motors...

Hello Fergus,

Will probably be worth asking this in the Arduino forum ? Although if Simon Monk pops in here (I have seen him in this forum a few times) he would probably be able to help, he is the authour of quite a few Arduino books.

Steve

This is the updated sketch:

[code]

/*

* Robot Motor Controller script with PWM speed control

*/

//---------------------- Motors

int motorL[] = {6, 7};

int motorR[] = {8, 9};

int ledPin = 13;

 

 

void setup() {

Serial.begin(9600);

int i;

for(i =0; i > 0; i < 0){

pinMode(motorL[i], OUTPUT);

pinMode(motorR[i], OUTPUT);

pinMode(ledPin, OUTPUT);

}

 

 

}

 

 

void loop() {

 

 

drive_forward();

if y > 0:

          digitalWrite(motorL[0], HIGH);

          digitalWrite(motorL[1], LOW);

          digitalWrite(motorR[0], HIGH);

          digitalWrite(motorR[1], LOW);

          analogWrite(9, motor_a);

          analogWrite(6, motor_b);

 

 

drive_backwards();

if y < 0:

          digitalWrite(motorL[0], LOW);

          digitalWrite(motorL[1], HIGH);

          digitalWrite(motorR[0], LOW);

          digitalWrite(motorR[1], HIGH);

          analogWrite(9, motor_a);

          analogWrite(6, motor_b);

 

}

I'm not sure what type of motors you're using, perhaps servos, looking at your code? You might want to look at Adafruit's page for some helpful tips http://www.ladyada.net/make/mshield/use.html

They are DC motors.  I CANNOT use AF library becasue I don't have their shield.

A couple of things:

What kind of controller you are using ?

You should not try to drive DC motors directly from a Arduino - or any inductive load.

Seems like you are mixing somewhat things.

The first one is like if you are using C and Python at the same time.

The second one is like you are mixing direction pins on a H Bridge - HIGH and LOW for one direction LOW and HIG for the reverse - with PWM speeds in the same pins.

I am going to address the "syntax" mix. I am sure that code you posted can't compile on the arduino IDE.

The pseudo-code you posted - that is not right - can be writen in C as:

int motorL[] = {6, 7};
int motorR[] = {8, 9};
int ledPin = 13;


void setup() {
  Serial.begin(9600);
  int i;
  for(i =0; i > 2; i++ ){
    pinMode(motorL[i], OUTPUT);
    pinMode(motorR[i], OUTPUT);
  }
  pinMode(ledPin, OUTPUT);

}


void loop() {
  if( y > 0 ){
    digitalWrite(motorL[0], HIGH);
    digitalWrite(motorL[1], LOW);
    digitalWrite(motorR[0], HIGH);
    digitalWrite(motorR[1], LOW);
    analogWrite(9, motor_a);
    analogWrite(6, motor_b);
  }else if(  y < 0 ){
    digitalWrite(motorL[0], LOW);
    digitalWrite(motorL[1], HIGH);
    digitalWrite(motorR[0], LOW);
    digitalWrite(motorR[1], HIGH);
    analogWrite(9, motor_a);
    analogWrite(6, motor_b);
  }
}

The main problem here is "y" is not declared nor defined so that's an error.

If you want to try PWM speed in the Arduino, connect one pin on the motor to ground the other to 6 and use that sketch:

void setup(){
  pinMode(6, OUTPUT);
}
void loop(){
  int i;

  for(i =0; i<255;i++){
    analogWrite(6,i);
    delay(500);
  }
}

Now going a bit further. The code you posted seem taken from an H-Bridge type DC motor controller like this one L298 2A 6V-50V Compact Dual Motor Driver Kit - RobotShop the Arduino motor shield is based in the same chip ST L298 Arduino - ArduinoMotorShieldR3

Those shield - and pretty much any H-Bridge - use to have 2 pins for direction and one for speed called the "enable" pin.

The direction pins for one motor use this truth table:

For the speed you use PWM on the enable PIN.

So with this in mind, the code you posted makes more sense.

The motor_R and motor_L pins are the direction pins for each motor and you would need another two pins for PWM.

The pseudo code for this kind of controller - without any comunication just the movement function - can be:

int direction_pin_motorL[] = {10, 11};
int direction_pin_motorR[] = {8, 9};
int speed_pin_motorL = 5;
int speed_pin_motorL = 6;

void setup(){
  int i;
  for(i =0; i > 2; i++ ){
     pinMode(motorL[i], OUTPUT);
     pinMode(motorR[i], OUTPUT);
  }
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
}

void loop(){
  // PUT HERE YOUR CONTROL CODE
}

void motor_L_speed(int speed){ // from 0 (stop) to 255
  analogWrite(speed_pin_motorL, speed); // PWM
}

void motor_R_speed(int speed){ // from 0 (stop) to 255
  analogWrite(speed_pin_motorR, speed); // PWM
}
 void motor_L_forward(){
  digitalWrite(direction_pin_motorL[1], HIGH);
  digitalWrite(direction_pin_motorL[0], LOW);  
 }

  void motor_R_forward(){
  digitalWrite(direction_pin_motorR[1], HIGH);
  digitalWrite(direction_pin_motorR[0], LOW);  
 }

  void motor_L_backward(){
  digitalWrite(direction_pin_motorL[1], LOW);
  digitalWrite(direction_pin_motorL[0], HIGH);  
 }

  void motor_R_backward(){
  digitalWrite(direction_pin_motorR[1], LOW);
  digitalWrite(direction_pin_motorR[0], HIGH);  
 }


void drive_forward(){ // both motors forward
  motor_L_forward();
  motor_R_forward();
 }

 void drive_backwards(){ // both motors forward
  motor_L_backward();
  motor_R_backward();
 }

Not sure if this is what you was looking for.