Is it okay to connect the TX of a UART controller to more than controllers RX, say I have a controller "A" sending some data to controller "B" and suddenly I want "C" also to recieve it?
More than 2 controllers in UART communication
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You can connect an output of any type to as many inputs as you wish as long as you don't exceed the drive limits of the output.
But rs485 works better than rs232 as a multiple drop bus. A possible Plan B is run tx from node1 to rx of 2, tx of 2 to rx of 3, tx of 3 to rx of 1 in a chain. Everyone reads every byte of every msg, but then forwards everything that isnt for his address. So if a msg is 10 bytes at 115200 (83usec), a pkt for node 3 would take about a ms to go from node 1 to node 2, another ms from node 2 to node 3. Two hops.
Depends on the 'system' plan... I use the same as the OP via 485... 5 bytes out, addressed slave returns 3 bytes.
when I try to wire the TX of one controller to more than one RX I find that the voltage is not rising above the threshold. Will it happen sometimes or is it a firmware issue?
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no. Both the controllers are able to transmit and receive independently. I doubled checked it.