First cut at DMX receiving code for Leonardo / Saikoduino

dmx_test.ino

#define RX_STATUS_PIN 13
#define RX_ENABLE_PIN 2
#define TX_ENABLE_PIN 3

volatile uint8_t  DmxRxField[8]; //array of DMX vals (raw)
volatile uint16_t DmxAddress;	 //start address

enum {IDLE, BREAK, STARTB, STARTADR}; //DMX states

volatile uint8_t gDmxState;

int red = 9;
int green = 10;
int blue = 11;
int bmix = 0;    // blue brightness
int fadeAmount = 1;    // how many points to fade the LED by

// the setup routine runs once when you press reset:
void setup()  { 

  pinMode(red, OUTPUT);
  pinMode(blue, OUTPUT);
  pinMode(green, OUTPUT);
  
  Serial.begin(250000); //Enable serial reception with a 250k rate
  pinMode(RX_STATUS_PIN, OUTPUT); //RX STATUS LED pin, blinks on incoming DMX data
  pinMode(RX_ENABLE_PIN, OUTPUT);
  pinMode(TX_ENABLE_PIN, OUTPUT);
  digitalWrite(RX_ENABLE_PIN, LOW);
  digitalWrite(TX_ENABLE_PIN, LOW);
  
  gDmxState= IDLE; // initial state
  DmxAddress = 3; // The desired DMX Start Adress

  interrupts();
} 

// the loop routine runs over and over again forever:
void loop()  { 
  analogWrite(blue, bmix);

  // change the brightness for next time through the loop:
  bmix = bmix + fadeAmount;

  // reverse the direction of the fading at the ends of the fade: 
  if (bmix == 0 || bmix == 20) {
    fadeAmount = -fadeAmount ; 
  }     
  // wait for 60 milliseconds to see the dimming effect    
  delay(60);                            
}

ISR(USART1_RX_vect) {
	digitalWrite(RX_STATUS_PIN, HIGH);
	static  uint16_t DmxCount;
	uint8_t  USARTstate= UCSR1A;    //get state before data!
	uint8_t  DmxByte   = UDR1;	    //get data
	uint8_t  DmxState  = gDmxState;	//just load once from SRAM to increase speed

	if (USARTstate &(1<<FE1))		//check for break
	{
		DmxCount =  DmxAddress;		//reset channel counter (count channels before start address)
		gDmxState= BREAK;
	}

	else if (DmxState == BREAK)
	{
		if (DmxByte == 0) gDmxState= STARTB;  //normal start code detected
		else			  gDmxState= IDLE;
	}

	else if (DmxState == STARTB)
	{
		if (--DmxCount == 0)	//start address reached?
		{
			DmxCount= 1;		//set up counter for required channels
			DmxRxField[0]= DmxByte;	//get 1st DMX channel of device
			gDmxState= STARTADR;
		}
	}

	else if (DmxState == STARTADR)
	{
		DmxRxField[DmxCount++]= DmxByte;	//get channel
		if (DmxCount >= sizeof(DmxRxField)) //all ch received?
		{
			gDmxState= IDLE;	//wait for next break
		}
	}
	digitalWrite(RX_STATUS_PIN, LOW);							
}