Arduino Mega, Adafruit Mega Shield, Adafruit Motot Shield

by kokopellix on Mon Feb 11, 2013 5:43 pm

The Arduino Mega associates digital pin 3 with Interrupt 1.

The AdaFruit motor shield associates Digital pin 3 with DC Motor #2 / Stepper #1 (activation/speed control).

I have built a robot using the Arduino Mega, AdaFruit Mega Shield, and AdaFruit Mega Shield and two DC motors. I used the Mega because I wanted to associate all bumper/cliff on/off switches with corresponding interrupts and needed as many interrupts as I could get.

When running, if pin 3 drops to zero, the right motor stops and the left motor starts and stops (steps?).

How can I manage some sort of compatibility or is this project doomed? Is there a Mega motor shield?

Stripped down code, involving only the motor running straight ahead and pin 3 (which I cannot seem to read) follows:

Code: Select all
//    Sketch:  motorCheck
//  Robot running motor check.

#include <AFMotor.h>
AF_DCMotor  rightMotor(1, MOTOR12_64KHZ);    // Right wheel motor
AF_DCMotor  leftMotor(2, MOTOR12_64KHZ);     // Left wheel motor

const  int  defaultDelay = 20;

int      leftCliffIntPin = 3;

void setup()
  Serial.begin(9600);   // start the serial port
  Serial.print("FORWARD = ");    Serial.println(FORWARD);
  Serial.print("BACKWARD = ");   Serial.println(BACKWARD);

//  Install pull-up resistors on pin
  pinMode(leftCliffIntPin, INPUT);     
  digitalWrite(leftCliffIntPin, HIGH);
  //  Start the motors

void loop()
    int  pinVal = digitalRead(leftCliffIntPin);
    if (pinVal == HIGH) Serial.println("High, high, high");
    else Serial.println("Low, low, low");
    Serial.println("Running forward.");   

void  runStraight(int  straightDelay)
  Serial.println("Forward, forward, forward.");
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Joined: Sat Oct 15, 2011 11:12 am

Re: Arduino Mega, Adafruit Mega Shield, Adafruit Motot Shield

by adafruit_support_bill on Mon Feb 11, 2013 6:43 pm

Re-allocating pins for the shield is complicated. It would require both hardware and library changes. A better approach is to use pin-change interrupts. These can work with many more pins than external interrupts:
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