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Hello, Maybe this is not a question for this forum, but I still give it a try: I would like to have different 8051's (or derivatives) "talking to each other" via a serial protocol. One uC would be a 'master'. The other ones should trigger the master when some info (decoded RC5-signal) is available. Since the different devices will be put quite far from each other (several meters, up to maybe 25 meters each), I think the RS232 protocol is not suitable anymore for this (distance too long). Therefore, I was thinking to use RS485, but I have to be honest: I don't know a lot of this protocol/standard. Can someone tell me where to find useful information about this protocol? Eventually sites where some C source code for the protocol is already available to give it a start? Does Keil have some useful example programs next to the tig amounts of other examples already available? I didn't find anything regarding RS485 myself on the site, but there might be some 'hidden places' with more useful information... Any help would be highly appreciated. Rgds, --Geert
For what it's worth, here's what I know. The primary difference between RS-232/422/485 is mainly the hardware used to generate the signal on the wires that connect various devices. For RS-232, that's typically a MAX232. RS-232 is single-ended and does not work well over long distances. RS-485 is differential (2 wires, + and -) and is better suited to handle noise. From the 8051 perspective, you still program the on-chip UART as normal. The big difference happens when you have multiple devices on the "bus". Then, you must handle some kind of protocol to communication between nodes. In fact, once you have more than 2 devices connected, you have created a network. At this point, I think there are a lot of things you should consider. Here are a few:
Thanks for the info! --Geert