Hi,

Interesting thing this is. Could you tell us which protocols you need to implement? Are they universal protocols like RS232 etc or are they something you will define yourself? Craig's idea of haveing a master-protocol that wraps over other protocols makes sense, but then that would mean the connected uCs ("clients" if u will) will also have to implement that master protocol... which I think is not what you may want.

What you are saying is your application will listen on a port, and based on the nature of the signals (handshake signals maybe) will decide which protocol it is. That seems a bit difficult....maybe instead of a master protocol as a whole and bundling all the data + meta-data into an unique protocol, you can come up with a preliminary master hand-shake signal, which will inform the listening application which type of protocol is going to be coming in. Once the listener knows what to expect, you can send away on the specific protocol. Maybe that's what craig meant too, only he was talking about more complex protocols like TCP.

As far as I can see, it will have to be a device driver (unless you intend to deploy it on DOS, which does not support multitasking). The device driver can communicate with a slightly higher-level application, with which the end-user applications will register. The middle-level software will maintain a list of which protocol goes to which application. On the software side, with the right design its do-able (in software, what isn't?)

My concerns are on the hardware / physical signal side. How will you know when multiple devices are writing to the same serial port simulataneously. One way is to have the device check if the bus is free at present before writing, but it is still possible that two(or more) devices write to a free bus simultaneously. You will need to come up with a pretty good method to resolve these "collisions". Then again if you can handle collisions, how will you assign priority to the next device that is allowed access?

I was thinking of building a simple RS-232 bus network of 3 old PCs at home over the serial port, thats when I came up with these issues. But I de-prioritzed that when I realized I'd have to delve into writing device drivers!

kundi