repeater/nexa.ino

enum { UNKNOWN, T0, T1, T2, T3, OK, DONE };

byte state = UNKNOWN;

       unsigned long x_data;
static unsigned int x_numBits;
static boolean x_2ndbit;

static unsigned int dbg_periodTime; // For debugging

static void resetDecoder () {
	x_data = 0;
	x_numBits = 0;
	x_2ndbit = false;
	state = UNKNOWN;
}

static boolean isDone() { return state == DONE; }

static void done () { state = DONE; }

static void gotBit (char value) {

	// X
	x_numBits++;
	x_data = (x_data << 1) + (value & 0x01);
	if( x_2ndbit == false ) {
		x_2ndbit = true;
	}
	else {
		x_2ndbit = false;
		unsigned int bits = (x_data & 0x03);
		if( bits == 2 ) {
			// Bit is 1
			x_data = (x_data >> 1) | 0x00000001;
		}
		else {
			// Bit is 0
			x_data = (x_data >> 1) & 0xFFFFFFFE;
		}
	}

	state = OK;
}

static int decode (unsigned int width) {

	switch (state) {
	case UNKNOWN: // Start of frame
		//printf("%8u\n",width);
		if ( 2400 <= width && width <= 3000 ) {
			state = T0;
			//dbg_periodTime = width;
		}
		break;

	case T0: // First half of pulse : HIGH around 230us

		if ( 150 <= width && width <= 300 ) {
			state = T1;
		}
                else if ( x_numBits == 0 && 2400 <= width && width <= 3000 ) {
			state = T0;
		}
		else return -1;	// error, reset
		break;

	case T1:
                if ( 200 <= width && width <= 400) {
			gotBit(0);
		} else if ( 1000 <= width && width <= 1500 ) {
			gotBit(1);
		} else if ( /*width > 5000 &&*/ x_numBits == 64) {	// end of frame
			state = DONE;
			return 1;
		} else  {
			return -1;
		}
		state = T0;
		break;
	}
	return 0;
}

#define TOO_SHORT 100

bool nextPulseNexa (unsigned int width) {

	if( width > 0 ) {
		if (state != DONE)

			switch (decode(width)) {
			case -1:
				resetDecoder();
				break;
			case 1:  done();  break;
		}
	}
	return isDone();
}