Pololu Micro Dual Serial Motor Controller

This tiny module can control two motors, 1 A peak each, and you can daisy-chain multiple units to control up to 62 motors with a single serial line. The new version provides up to 2 A to a single motor, or 1 A each to two motors. The motor supply can be as low as 2 V, making the unit a perfect match for small DC motors. Using one serial output from your microcontroller, you can independently set each motor to go forward or backward at any of 127 speeds, coast, and brake.

The controller takes up almost no space on a breadboard or PCB:

Sample control code for Arduino:

#include <softwareserial.h>

#define LEFT_MOTOR  2
#define RIGHT_MOTOR 3

#define FORWARD 1
#define REVERSE 0


byte motor_controller_pin = 3;
byte motor_controller_reset_pin = 4;

// for rx on all unidirectional software serial objects
byte unused_pin = 10;


unsigned char mc_command[4];

SoftwareSerial motor_controller = SoftwareSerial(unused_pin, motor_controller_pin);


//==========================================================================================

void setup()
{
   pinMode(motor_controller_pin, OUTPUT);
   pinMode(motor_controller_reset_pin, OUTPUT);
   pinMode(unused_pin, INPUT);

   motor_controller.begin(9600);

   mc_init();
}

//==========================================================================================

void loop()
{
   // accelerate forward
   for(int i = 0; i <= 130; i += 10)
   {  
      mc_send_command(LEFT_MOTOR, FORWARD, i);
      mc_send_command(RIGHT_MOTOR, FORWARD, i);

      delay(250);
   }

   delay(3000);

   // decelerate
   for(int i = 130; i >= 0; i -= 10)
   {
      mc_send_command(LEFT_MOTOR, FORWARD, i);
      mc_send_command(RIGHT_MOTOR, FORWARD, i);

      delay(250);
   }

   delay(3000);

   // accelerate backward
   for(int i = 0; i <= 130; i += 10)
   {
      mc_send_command(LEFT_MOTOR, REVERSE, i);
      mc_send_command(RIGHT_MOTOR, REVERSE, i);

      delay(250);
   }

   delay(3000);

   // decelerate
   for(int i = 130; i >= 0; i -= 10)
   {
      mc_send_command(LEFT_MOTOR, REVERSE, i);
      mc_send_command(RIGHT_MOTOR, REVERSE, i);

      delay(250);
   }

   delay(3000);
}


//==========================================================================================


void mc_init()
{
   // start up motor controller
   digitalWrite(motor_controller_reset_pin, HIGH);

   // let motor controller wake up
   delay(100);
}


void mc_send_command(byte motor, byte direction, byte speed)
{
   direction = constrain(direction, 0,   1);
   speed     = constrain(speed,   0, 127);

   mc_command[0] = 0x80; // start byte
   mc_command[1] = 0x00; // Device type byte
   mc_command[2] = (2 * motor) + (direction == FORWARD ? FORWARD : REVERSE); // Motor number and direction byte
   mc_command[3] = speed; // Motor speed (0 to 127)

   // send data
   for(int i = 0; i < 4; i++)
   { motor_controller.print(mc_command[i], BYTE); }
}