Reassign pin in AFMotor.h


I’m working on an RC project where I use an Adafruit motor shield and plan on using NRF24L01 transceivers.

The problem is that the Motorshield uses pin 12 , but so does the NRF24L01 antennae.

To try and counter this problem I wanted to use a different pin then pin 12 for my shield. The datasheet of the shield says that pin 2 isn’t used.
So I used a jumper from pin 2 to pin 12 (on the shield) and I cut off the pin from the shield so it isn’t connected to pin 12 of my Arduino.

Of course this isn’t going to work just like that so I searched the library of the shield (AFMotor.h) to see where pin 12 is declared and replaced it by pin 2.

// Arduino pin names for interface to 74HCT595 latch
#define MOTORLATCH 2 //(previously 12)
#define MOTORCLK 4
#define MOTORDATA 8

I searched the whole library for other mentions of this pin but couldn’t find any (not even in the cpp file).

As you can already guess (since I’m writing this post) this didn’t work.

I looked on this forum and found two similar threads but neither of them offered a solution.
I wonder if there simply isn’t a solution, or if no solution was given yet.

Preferably I want to make it work like this but If there is no solution I would like to understand why.

Here are the threads I found:

And here is the complete library code (with my adjustement):

// Adafruit Motor shield library
// copyright Adafruit Industries LLC, 2009
// this code is public domain, enjoy!

 * Usage Notes:
 * For PIC32, all features work properly with the following two exceptions:
 * 1) Because the PIC32 only has 5 PWM outputs, and the AFMotor shield needs 6
 *    to completely operate (four for motor outputs and two for RC servos), the
 *    M1 motor output will not have PWM ability when used with a PIC32 board.
 *    However, there is a very simple workaround. If you need to drive a stepper
 *    or DC motor with PWM on motor output M1, you can use the PWM output on pin
 *    9 or pin 10 (normally use for RC servo outputs on Arduino, not needed for 
 *    RC servo outputs on PIC32) to drive the PWM input for M1 by simply putting
 *    a jumber from pin 9 to pin 11 or pin 10 to pin 11. Then uncomment one of the
 *    two #defines below to activate the PWM on either pin 9 or pin 10. You will
 *    then have a fully functional microstepping for 2 stepper motors, or four
 *    DC motor outputs with PWM.
 * 2) There is a conflict between RC Servo outputs on pins 9 and pins 10 and 
 *    the operation of DC motors and stepper motors as of 9/2012. This issue
 *    will get fixed in future MPIDE releases, but at the present time it means
 *    that the Motor Party example will NOT work properly. Any time you attach
 *    an RC servo to pins 9 or pins 10, ALL PWM outputs on the whole board will
 *    stop working. Thus no steppers or DC motors.
// <BPS> 09/15/2012 Modified for use with chipKIT boards

#ifndef _AFMotor_h_
#define _AFMotor_h_

#include <inttypes.h>
#if defined(__AVR__)
    #include <avr/io.h>

    //#define MOTORDEBUG 1

    #define MICROSTEPS 16                       // 8 or 16

    #define MOTOR12_64KHZ _BV(CS20)             // no prescale
    #define MOTOR12_8KHZ _BV(CS21)              // divide by 8
    #define MOTOR12_2KHZ _BV(CS21) | _BV(CS20)  // divide by 32
    #define MOTOR12_1KHZ _BV(CS22)              // divide by 64

    #define MOTOR34_64KHZ _BV(CS00)             // no prescale
    #define MOTOR34_8KHZ _BV(CS01)              // divide by 8
    #define MOTOR34_1KHZ _BV(CS01) | _BV(CS00)  // divide by 64
    #define DC_MOTOR_PWM_RATE   MOTOR34_8KHZ    // PWM rate for DC motors
    #define STEPPER1_PWM_RATE   MOTOR12_64KHZ   // PWM rate for stepper 1
    #define STEPPER2_PWM_RATE   MOTOR34_64KHZ   // PWM rate for stepper 2
#elif defined(__PIC32MX__)
    //#define MOTORDEBUG 1
    // Uncomment the one of following lines if you have put a jumper from 
    // either pin 9 to pin 11 or pin 10 to pin 11 on your Motor Shield.
    // Either will enable PWM for M1
    //#define PIC32_USE_PIN9_FOR_M1_PWM
    //#define PIC32_USE_PIN10_FOR_M1_PWM

    #define MICROSTEPS 16       // 8 or 16

    // For PIC32 Timers, define prescale settings by PWM frequency
    #define MOTOR12_312KHZ  0   // 1:1, actual frequency 312KHz
    #define MOTOR12_156KHZ  1   // 1:2, actual frequency 156KHz
    #define MOTOR12_64KHZ   2   // 1:4, actual frequency 78KHz
    #define MOTOR12_39KHZ   3   // 1:8, acutal frequency 39KHz
    #define MOTOR12_19KHZ   4   // 1:16, actual frequency 19KHz
    #define MOTOR12_8KHZ    5   // 1:32, actual frequency 9.7KHz
    #define MOTOR12_4_8KHZ  6   // 1:64, actual frequency 4.8KHz
    #define MOTOR12_2KHZ    7   // 1:256, actual frequency 1.2KHz
    #define MOTOR12_1KHZ    7   // 1:256, actual frequency 1.2KHz

    #define MOTOR34_312KHZ  0   // 1:1, actual frequency 312KHz
    #define MOTOR34_156KHZ  1   // 1:2, actual frequency 156KHz
    #define MOTOR34_64KHZ   2   // 1:4, actual frequency 78KHz
    #define MOTOR34_39KHZ   3   // 1:8, acutal frequency 39KHz
    #define MOTOR34_19KHZ   4   // 1:16, actual frequency 19KHz
    #define MOTOR34_8KHZ    5   // 1:32, actual frequency 9.7KHz
    #define MOTOR34_4_8KHZ  6   // 1:64, actual frequency 4.8KHz
    #define MOTOR34_2KHZ    7   // 1:256, actual frequency 1.2KHz
    #define MOTOR34_1KHZ    7   // 1:256, actual frequency 1.2KHz
    // PWM rate for DC motors.
    #define DC_MOTOR_PWM_RATE   MOTOR34_39KHZ
    // Note: for PIC32, both of these must be set to the same value
    // since there's only one timebase for all 4 PWM outputs
    #define STEPPER1_PWM_RATE   MOTOR12_39KHZ
    #define STEPPER2_PWM_RATE   MOTOR34_39KHZ

// Bit positions in the 74HCT595 shift register output
#define MOTOR1_A 2
#define MOTOR1_B 3
#define MOTOR2_A 1
#define MOTOR2_B 4
#define MOTOR4_A 0
#define MOTOR4_B 6
#define MOTOR3_A 5
#define MOTOR3_B 7

// Constants that the user passes in to the motor calls
#define FORWARD 1
#define BACKWARD 2
#define BRAKE 3
#define RELEASE 4

// Constants that the user passes in to the stepper calls
#define SINGLE 1
#define DOUBLE 2
#define INTERLEAVE 3
#define MICROSTEP 4

#define LATCH 4

#define CLK_DDR DDRD
#define CLK 4

#define ENABLE 7

#define SER 0
#define SER_DDR DDRB

// Arduino pin names for interface to 74HCT595 latch
#define MOTORLATCH 2 //(previously 12)
#define MOTORCLK 4
#define MOTORDATA 8

class AFMotorController
    void enable(void);
    friend class AF_DCMotor;
    void latch_tx(void);
    uint8_t TimerInitalized;

class AF_DCMotor
  AF_DCMotor(uint8_t motornum, uint8_t freq = DC_MOTOR_PWM_RATE);
  void run(uint8_t);
  void setSpeed(uint8_t);

  uint8_t motornum, pwmfreq;

class AF_Stepper {
  AF_Stepper(uint16_t, uint8_t);
  void step(uint16_t steps, uint8_t dir,  uint8_t style = SINGLE);
  void setSpeed(uint16_t);
  uint8_t onestep(uint8_t dir, uint8_t style);
  void release(void);
  uint16_t revsteps; // # steps per revolution
  uint8_t steppernum;
  uint32_t usperstep, steppingcounter;
  uint8_t currentstep;


uint8_t getlatchstate(void);


I'd suggest asking on the Adafruit forum.


Thanks for the reply.

I asked my question there, but they refuse to help since the V1 board is discontinued and they no longer offer support for questions concerning that topic.

I did find an old thread on that forum.
He had the exact same problem and exact same solution as me (as far as I know) but it still does not work for me.

Here is the link to the thread.