Software conflict between Servo library and separate PWM'ed pin.

Using Arduino Programming Questions
1

Hello everyone,

I have been troubleshooting all day trying to solve a little problem I have run into. I own a TB6612FNG Dual Motor Driver Carrier from Pololu, and have been working on a project that involves the use of that motor driver and a servo.

If I only include code to run the motor driver:

#define MOT_IN_A1 13 // motor input 1
#define MOT_IN_A2 12 // motor input 2
#define MOT_A_PWM 10 // motor speed, determined by PWM
#define STANDBY 11 // motor driver enable/disable
#define LED 9 // status LED

void setup(){
  DDRB = 0xFF; // set all port B pins to OUTPUT mode
  digitalWrite(STANDBY, HIGH); // enable motor driver
  digitalWrite(LED, HIGH); // turn status LED on
  analogWrite(MOT_A_PWM, 100); // set speed for motor driver to 100 (of a maximum of 255), approx. 40% power.
}

void loop(){
  digitalWrite(MOT_IN_A1, HIGH);
  digitalWrite(MOT_IN_A2, LOW);
  
  delay(2000);

  digitalWrite(MOT_IN_A2, HIGH);
  digitalWrite(MOT_IN_A1, LOW);

  delay(2000);
}

Everything works perfectly.

However, as soon as I create a Servo object and attach it to a PWM enabled pin (pin 3 in this case):

#include <Servo.h>

#define MOT_IN_A1 13 // motor input 1
#define MOT_IN_A2 12 // motor input 2
#define MOT_A_PWM 10 // motor speed, determined by PWM
#define STANDBY 11 // motor driver enable/disable
#define LED 9 // status LED

Servo s;

void setup(){
  s.attach(3); // digital PWM enabled pin 3 on arduino
  DDRB = 0xFF; // set all port B pins to OUTPUT mode
  digitalWrite(STANDBY, HIGH); // enable motor driver
  digitalWrite(LED, HIGH); // turn status LED on
  analogWrite(MOT_A_PWM, 100); // set speed for motor driver to 100 (of a maximum of 255), approx. 40% power.
}

void loop(){
  digitalWrite(MOT_IN_A1, HIGH);
  digitalWrite(MOT_IN_A2, LOW);
  
  delay(2000);

  digitalWrite(MOT_IN_A2, HIGH);
  digitalWrite(MOT_IN_A1, LOW);

  delay(2000);
}

The motor driver no longer moves the motor.
I do have a good power supply so I do not believe that is the problem.

I really have no idea why this is happening, and my google-fu hasn't brought anything relevant up. Thanks to anyone who can help =).

2

The Servo library uses a timer that is also used to PWM pins 9 and 10. Can you use different pins for the motor driver?

3

Oh perfect! I had a feeling it was something to do with pins sharing the same timer. I can change the pin-out configuration no problem. Thanks for the help! =D

4