1        0       end
 _       _        __
| |_    | |__    |  |
650/520 650/1100 1850

OOOMMXXXXXXXXRCC

OOO - regular command 000
    - turn off        001
MM - current mode
R - 0 for initial press, 1 for repeat
CC - checksum -- every two bits, XORed (see pseudocode below)
XXXXXXXX - button code

BUTTON CODES:

star:		01111111
triangle:	11110111
circle:		11101111
square:		11011111
heart:		10111111
cloud:		11111011
roll:		11111101
mode set:	11111111
exit:		11111110
release (all):	00000000 (R can potentially be set or unset!)
turn off:	11111111 (x2, with OOO set to 001)

NOTES:

- When holding down a button, pressing a second button causes that button code to start
without a release code in between.  Afterwards, the release code may have the repeat bit set.

- Neither "mode set" nor "turn off" use release codes.  "Mode set" specifies the new mode
with the MM bits.

CHECKSUM CALCULATION PSEUDOCODE:

int checksum = 0;
int bitpair = 0;
for (int ibit = 0; ibit < 15; ibit ++)
{
	if (ibit % 2 == 0)
		bitpair = bitstream[ibit] << 1;
	else
	{
		bitpair = bitpair | bitstream[ibit];
		checksum = checksum ^ bitpair;
	}
}