Originally posted by Dean Roddey
And finally the channel change is working. It was lack of documentation so I had no idea I wasn't doing something I should have been doing.
The "FA protocol" was apparently developed jointly by RCA and Sony for their lines of DirecTV receivers, and they consider it to be "proprietary" (i.e., they refuse to publish their own documentation for us "common folk", although they do
provide protocol documentation under "non-disclosure agreements" to "industry partners" such as TiVo).
The protocol was "reverse engineered" years ago by hobbyists, and the code lists for the original ("MPG") and current ("APG") versions of the protocol are published on two Web sites. (I have posted those URLs previously.) Unfortunately, the hobbyist documentation is unclear about the fact that all commands involving parameters are done in a "two-part transaction".
The way I figured it out was, I wrote a "serial sniffer" in Java. This uses two serial ports, and it simply copies the input on one port as output to the other, and vice versa. But it logs
all data flows to the console. Then, with the hobbyist documentation in hand, I connected a TiVo to a Sony DBS receiver (an early "MPG" model, initially) via my "sniffer"and examined the log!