MIDI data bytes are 7 bits, meaning they can have decimal values from 0 to 127.
In a 7-bit binary number:
the bit on the right represents a decimal value of 1.
the next bit to the left represents a decimal value of 2.
the next bits to the left represent decimal values of 4, 8, 16, 32, and 64.
Decimal values from 0 to 127 can be expressed in seven ...
Well, I am not (yet) an expert, but since I work in embedded software now I'd guess that this is your problem:
MXC MTD nand Driver 2.5
NAND device: Manufacturer ID: 0x20, Chip ID: 0xaa (ST Micro NAND 256MiB 1,8V 8-bit)
Searching for RedBoot partition table in NAND 256MiB 1,8V 8-bit at offset 0xff60000
No RedBoot partition table detected in NAND 256MiB ...
The fact that this value is not checksummed (as I understand?) is very confusing but it might suggest either:
the protocol really doesn't care about bit flips in this value (and needn't drop the packet in that case)
the value is not yet known during the checksumming process
I really don't have a clue, if I had to take a shot in the dark I'd say this is ...
Without access to the code it’s hard to say for sure but I think it’s some kind of sequence number. I’d suggest trying to record as many sequences as you can and try sending the replay on your own to see if you get the same responses.