ledRingDisplay.ino

byte muxCount = 0;
byte lookup[17]={0,1,2,4,8,1,2,4,8,1,2,4,8,1,2,4,8};

void displayRing(byte number) {
	byte groupMin = (4 * muxCount) + 1;
	byte groupMax = (4 * muxCount) + 4;
	byte A = 0;
	byte B = 0;
	if (number > 0) {
		if ( (number >= groupMin) && (number <= groupMax) ) {
			A = lookup[number];
			B = 1 << muxCount;
		}
	}

	byte PORT;
	PORT = (B << 4) + A;

	muxCount++;
	muxCount = muxCount % 4;
}