Spark embedded application code (like Arduino/Wiring code) to drive an RC car with the Spark API.

rc-car.c

#include <stdlib.h>

// Motor shield instructions (set control mode jumpers to PWM mode)
// http://www.dfrobot.com/wiki/index.php?title=Arduino_Motor_Shield_(L298N)_(SKU:DRI0009)

#define LEFT  A7  // Motor Shield E1, Arduino D6
#define RIGHT D1  // Motor Shield E2, Arduino D5

void setup()
{
  pinMode(LEFT, OUTPUT);
  pinMode(RIGHT, OUTPUT);
}

void loop()
{
}

// Callback triggered by the Spark API
// See the "Custom Messages" section of
// http://docs.sparkdevices.com/
char userFunction(char *message)
{
  long val = strtol(message + 1, NULL, 10);
  if ('L' == *message)
  {
    analogWrite(LEFT, val);
    return 1;
  }
  else if ('R' == *message)
  {
    analogWrite(RIGHT, val);
    return 2;
  }
  return 0;
}