Sweet Chariot Code

serial_com_arduino.ino

int incomingByte;      // a variable to read incoming serial data into

int pwm_a = 5;  //PWM control for motor outputs 1 and 2 
int pwm_b = 9;  //PWM control for motor outputs 3 and 4 
int dir_a = 4;  //direction control for motor outputs 1 and 2 
int dir_b = 8;  //direction control for motor outputs 3 and 4 

void setup() {
  // Initialize serial communication on UART TX/RX
  Serial.begin(9600);

  // LED on Arduino
  pinMode(13, OUTPUT); 

  // Set control pins to be outputs
  pinMode(pwm_a, OUTPUT);  
  pinMode(pwm_b, OUTPUT);
  pinMode(dir_a, OUTPUT);
  pinMode(dir_b, OUTPUT);
}

void loop() {
  // See if there's incoming serial data
  if (Serial.available() > 0) {
    // Read the oldest byte in the serial buffer
    incomingByte = Serial.read();
    
    // If it's a capital H (ASCII 72), turn on the LED:
    if (incomingByte == 'H') {
      digitalWrite(13, HIGH);
    }
    // If it's an L (ASCII 76) turn off the LED:
    if (incomingByte == 'L') {
        digitalWrite(13, LOW); 
    }

    if (incomingByte == 'D') {
        analogWrite(pwm_a, 255);  
        analogWrite(pwm_b, 255);
       
        delay(1000);
        
        analogWrite(pwm_a, 0);  
        analogWrite(pwm_b, 0);
    }

    if (incomingByte == 'F') {
        digitalWrite(dir_a, LOW); 
        digitalWrite(dir_b, HIGH); 
    }

    if (incomingByte == 'R') {
        digitalWrite(dir_a, HIGH); 
        digitalWrite(dir_b, LOW); 
    }
  }
}

serial_com_photon.ino

/* Function prototypes -------------------------------------------------------*/
int sendLightOn(String dummy);
int sendLightOff(String dummy);
int drive(String dummy);
int reverse(String dummy);
int forward(String dummy);

void setup()
{
  // Initiate Serial Communication on UART TX/RX.
  Serial1.begin(9600);
    
	//Register all the Tinker functions
	Spark.function("sendlighton", sendLightOn);
	Spark.function("sendlightoff", sendLightOff);
	Spark.function("drive", drive);
	Spark.function("reverse", reverse);
	Spark.function("forward", forward);
}

void loop()
{
}

int sendLightOn(String dummy)
{
    Serial1.write('H');
    return -1;
}

int sendLightOff(String dummy)
{
    Serial1.write('L');
    return -1;
}

int drive(String dummy)
{
    Serial1.write('D');
    return -1;
}

int reverse(String dummy)
{
    Serial1.write('R');
    return -1;
}

int forward(String dummy)
{
    Serial1.write('F');
    return -1;
}