Can I get a copy of the protocol for the (insert phone model here)?
We don't have any formal documentation of the protocols in use.
The best source we can offer is the knowledge assembled by Nagy Balazs
and Marcin Wiacek. You can find result of their work in
subdirectory in gnokii sources (you can browse the CVS copy of this directory here). Note that not all known protocol functions
are implemented in gnokii and that some details of the implementations aren't explained in the docs (so check the C source files too, CVS copies are here).
Nokia 6210 FBUS protocol description in C++ can be found in this wiki here.
You can see all frames sent and received running gnokii in debug mode (set
debug = on in the config file).
Alternatively there are some web sites that have collated some information:
If you find the previous pages hard to read, there's a good introduction to FBUS protocol.