Originally Posted by Putput
Y E S
(did you hear it ?)
Well, of course it works *much* better once signal is not inverted :-) - Thanks a thousand times, Ale !
By the way, I used the 18k resistor in series with the incoming line and it works perfectly. Schema and scope traces will come soon but ... what we all are interested in is hex dumps, aren't we ?
So here we go. You'll find below a zip file containing two traces.
The first one with a CD playing track 1 of CD1 for a long time, then I began skipping to tracks 2,3,4,5 (and 6 maybe ?), each time trying to wait for 5 seconds before going to the next track.
For the second one, I skipped to CD 1 (which was already playing and restarted at the beginning of track 1 ) then CD 2, 3, 4, 5, 6 and back to 1, each time also trying to wait for 5 seconds of song playing before going to the next CD
A word about the way the traces were taken : I'm using the MTTTY samples as I already said, but modified in the following ways :
- dump byte in hex and binary formats, plus ascii character if in the 32-127 range (or something like that)
- only dump one byte per line
- connect to a second serial port at the same time. All bytes coming from the second serial port are indented to the right, making a second column.
- dump results to file
(sources or exe available on request, but beware, it's quick and dirty...)
The "dual channel" sometimes gives display problems when both threads try to write on screen at the same time, so sometimes you get things like :
which should read :
47h 01000111b G
01h 00 C5h 11000101b
I also have a systematic error on "SetCommState" on start, and the program even crashed once after a "long" session (the first file "playing + track changes"), but well, it's just a spying prototype :-)
47h 01000111b G
If I have time, I'll change the app to have a timestamp at the start of each line and also be more systematic and providing a timestamped description of the operations I made, but I'm afraid the week-end will be very busy...
Who'll be the first to crack this protocol ? :-)
Tip : Left column is what the CD Changer says, right (indented) column is what the head unit says.
On your marks... get set... Go !
(Oh, and yes, please, post your findings as soon as you have even a very partial decoding, so that others can use it. Thanks)