In Citroen and Peugeot the remote is precoded with the transponder. Changing transponder makes the remote stop working. In other words transponder and remote are matched in factory. When you program new transponder it must contain also data for remote. This is needed for BSI module to recognize rf transmissions from the remote.
You can reuse old remotes if you know what kind of data to write into transponder. It is placed in USER 0,1,2,3 pages in PCF7936.
Actual problem is retrieving data from an old, used remote and then put it into blank transponder.
Here is a way to get this data. We need several things to do this: some used (but still working) remotes with fresh battery.
A kind of "reader" based on PIC12F629 and a way to get the data into PC (I use so called USB-to-TTL converter), only RX channel needed and software is the ordinary HyperTerminal for windows (or some of xxxCOM apps if you're using Linux)
Here are the pads used on the remote.
Next part coming soon ...
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