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MrPerfectionest · 03-23-2005, 09:56 PM

Wow. That protocol is exactly the same one that was used by the head unit to communicate with the CD changer in my Audi, which was a panasonic or matsushista (sp?) unit.

When I was doing my initial research I found this information:

Quote:

The protocol panasonic uses is of the serial sync. type. There is one data line, a clock line and a sync line the changer uses to send data to the radio.
The radio to changer communication is done by some signals known from standard IR remote controls (without a carrier) using one dataline.
This remote control signal is pulse width modulated,the dataline is active high.
After an initail high(9ms) low(4.5ms) there follows a 32 bit sequence with a 0 encoded as 550us high,550us low and a 1 as 550us high,1.7ms low.
If the low pulse in the init phase is only 2.25ms long it is just a signal send periodical when a key is hold down and there are no data bits.
The data is transfered lsb first, the 1st byte is 0xFF-0th byte and the 3rd byte is 0xFE-2nd byte.The 2nd byte is the command.

The changer to radio communication transfers the data in bytes msb first, the data is valid at the falling clock edge and a low pulse of one half clock period is sent after the first and the last byte of the transfer on the sync line..The clock period is arround 8us.

There was only one packet containing state, time, disc and track information.

I do remember something about that description not being exactly right (I think having to do with the ordering of the bytes between LSB and MSB). I was going to take a circuit to a working product and hoped to make a little money off of it but I ended up having to head off to Germany and I sold my Audi when I got back.

I ended up accomplishing it with a polling routine first as proof of concept only because I couldn't get the pulse capture to behave right. Fortunately, the bit information is coded always with the high pulse first so the polling routine was easy to "lock on" to the signal.

If you want I can dig up some more information on it but it seems like you are almost there as it is.

03-23-2005, 09:56 PM	#15
MrPerfectionest Variable Bitrate Join Date: Apr 2004 Posts: 228	Wow. That protocol is exactly the same one that was used by the head unit to communicate with the CD changer in my Audi, which was a panasonic or matsushista (sp?) unit. When I was doing my initial research I found this information: Quote: The protocol panasonic uses is of the serial sync. type. There is one data line, a clock line and a sync line the changer uses to send data to the radio. The radio to changer communication is done by some signals known from standard IR remote controls (without a carrier) using one dataline. This remote control signal is pulse width modulated,the dataline is active high. After an initail high(9ms) low(4.5ms) there follows a 32 bit sequence with a 0 encoded as 550us high,550us low and a 1 as 550us high,1.7ms low. If the low pulse in the init phase is only 2.25ms long it is just a signal send periodical when a key is hold down and there are no data bits. The data is transfered lsb first, the 1st byte is 0xFF-0th byte and the 3rd byte is 0xFE-2nd byte.The 2nd byte is the command. The changer to radio communication transfers the data in bytes msb first, the data is valid at the falling clock edge and a low pulse of one half clock period is sent after the first and the last byte of the transfer on the sync line..The clock period is arround 8us. There was only one packet containing state, time, disc and track information. I do remember something about that description not being exactly right (I think having to do with the ordering of the bytes between LSB and MSB). I was going to take a circuit to a working product and hoped to make a little money off of it but I ended up having to head off to Germany and I sold my Audi when I got back. I ended up accomplishing it with a polling routine first as proof of concept only because I couldn't get the pulse capture to behave right. Fortunately, the bit information is coded always with the high pulse first so the polling routine was easy to "lock on" to the signal. If you want I can dig up some more information on it but it seems like you are almost there as it is.