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Head unit command frames
Quickly, before going to sleep, head unit commands have the same format as already said, and they seem to only reflect what is pressed, not the intended operation. That is, if you are on track 1 and press next, the message is "NEXT TRACK", not "GO TO TRACK 2".
"NEXT" frame is for example :
3D 07 02 17 01 2E
3D (classical frame start)
07 (frame id)
02 (data length)
17 (data type)
01 (data)
2E (fcs)
So actual "data" bytes are "17 01", which could mean "skip 1". I'd be interested in trying "17 02" :-)
Similarly, frame for "PREVIOUS" command is for example
3D 0F 03 22 01 02 10
from which data is "22 01 02" (3 bytes long)
There is also frequently an erroneous bit in the 'length' part, at the most significant (or sign) position : one can find 83h where it should be 03h. No idea if it's a decoding error or a bit set for an unknown purpose...
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