RYO network

["Pete Shew" <ukha_d@xxxxxxxxxxxxxxxxxx>]

I've got a requirement to connect a few PICs together and Cat 5 seems the
logical choice for physical media. However, I need to choose a protocol.
CAN looks a likely candidate, but I'm working with PIC 17F877A and not the
much nicer PIC 18F458 and don't have the luxury of an inbuilt CAN engine.
The reason - I only have version 1 of the ICD.

I also have space limitations and don't want to add an external CAN chip.

I don't want a bus master network, though if the case were strong enough I
could be persuaded., So I've currently got the idea of using CAN bus
drivers driven using a standard UART with extra logic to detect
recessive/dominant collisions, and with a protocol loosely based on CAN
within the limitations of the hardware. The pseudo code looks like it
should work OK, but I know that debugging is going to be
"interesting".

Has anyone else been along this route with success or failure? Any good
reasons why I should shell out for an ICD 2 (or even switch
microprocessors) and use pukka CAN?

HA? - it's part of my central heating control.

Pete