This is one I've always been too lazy to figure out, but now I may need to know.

Can someone enumerate all of the serial ports available on the empeg and which ones are duplicates, please? I know about the one on the back of the unit, obviously, I know about the one hanging off the back of the sled. These two are the same thing, are they not? And then isn't there one on the tuner somehow? Is this the same as the port used to deal with the Sony stalk control?

I'm thinking about writing something to attach my empeg to my car's CANbus and want to figure out the best way to get it interfaced.

Back of empeg and docking sled are the same port. The IrDA port is another serial port and finally one is used to control the tuner. The Sony stalk is just a bunch of resistors connected to switches and it's attached to the PIC inside the tuner module.

So there could conceivably be another serial port available if I wasn't using the tuner?

Yeah. There are two free serial ports in a tunerless Empeg. The IrDA one isn't used unless you add software like Palantir.

/dev/ttyS0 = Tuner
/dev/ttyS1 = Sled/Back port
/dev/ttyS2 = IrDA

The tuner one is the one most easily interfaced to. The IrDA one will require you opening up the empeg and unsoldering the IrDA transceiver chip and somehow routing the wires out. The tuner interface is TTL so be careful as it's connected to the StrongARM.

Hijack has several hooks into the kernel drivers for the Tuner port, so be wary of pitfalls when poking around there..

Well, unfortunately (?), I have a tuner, so I guess I'll try to work with the console. Of course, I'll have to figure out how to avoid sending garbage on the CANbus, which may be less than easy. Maybe I'll have to try to get something going with the IRDA port.