Hi,
I would like to implement IR communication between two uCs.
Moving or not?
Why not a bit of wire (cheap)?
Over how large a distance?
Are an ir led and photoresistor suitable? What sort of range would I get?
It depends of what you want to accomplish and at what distance.
I have made (un-modulated) main frame interfacing at 9600 bps with IR LED's and photo diodes, but the distance was only a few mm. I removed most of the pins in D-Sub25 connectors to make room for 5 lines of IR and used the few remaining pins for charging the data loggers while they uploaded their data to the main frame and while it may sound a bit over the top, the charging was necessary, as they were only uploaded after a lot of logging, so the batteries were on the brink already and the power to the IR would often bring them down, demanding endless retransmissions or causing data loss. They needed an optical solution, as they started out with wired transfer over D-Sub25, but they connected and disconnected often enough to kill the best gold plated connectors we could find in about a month and then the transmission went haywire.
With even a modest distance the speed falls drastically, as error correction request retransmission of packets.
Next step up is to use a modulated carrier, but that won't give you that much of a data rate.
If you need a high speed IR connection, take a look at IrDA transceivers, they don't use a carrier wave, but short pulses, but will be quite usable at a short distance.
Higher speed or larger distance and you need radio.