I was advised to use RS485 since I have about 7 devices needing to talk to each other (and cannot get CAN to work).
Although I want to start simple (two devices where one sends and other receives), later there might be multiple senders. One of the can be seen as Master, but others also should be able to initiate messages. So I need some kind of polling protocol.
The problem is, in RS-485 every time a device sends a message, all devices will 'hear' it and have to process it (although it's mostly checking one byte to know it's not meant for them).
But if I would get like 100,000 messages per second (worst case), this still cost a lot of processing time. And the master device (who initiates most) needs to do quite some non communication related processing.
How can I reduce the polling? I was thinking of decoupling the master device directly from RS-485 by adding some kind of communication device that passes RS-485 back/forth the master (e.g. via SPI). However, this seems a strange solution (converting back/forth all messages via SPI, also latency will be affected).
Or using some dedicated line (like one of the RS485-A/B lines) that devices can set HIGH to announce they have data. But I'm not sure if I should treat this equally as a RS-485 signal (so essentially having 1.5 RS-485 signals).