Quote: Originally Posted by pippolippi
It seems that the CDC replies with an acknowledgment (C5, I don't use ACK since it's ascii code 06) when it receives a command (disclaimer: I only looked at the first version of the dump without the reformatting, so I don't know if command/reply are synchronized).
Yes, you're right, the acknowledgement byte (C5h) is not the ACK character. And indeed, it's send by the head unit as a reply after each frame coming from the CDC, but also by the CDC after each command coming from the head unit, so it's really an "OK" message.
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Also note that 3D and 3F only differ in one bit (2), maybe the bit is used to signal something.
Yes, indeed.
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Can you try to capture the communication while powering up the HU and with the cd player not playing?
I'll do my best to have a more complete capture, along with annotated operations, but I have to tweak the capture program first. I think I'll dump Rx and Tx into separate files, with each byte being timestamped and numbered, so that I can then mix them in Excel or something.
I'm thinking of the following operations :
start capture from scratch / head unit off / head unit on, with tuner as source / switch to CD changer / play / pause / next/previous tracks / change CD / fast forward/backward / random / switch back to tuner / head unit off