What is the basic requirement to implement RDM?

[wcai_cypress]

Dear Nigel,

Your answer is definitely useful for me.
Now, I have the idea to implement RDM Responder based on UART, thanks!

Because I am a firmware engineer, I have one more stupid question, normally, the UART module in MCU works in full-duplex mode, how to make it work in half-duplex mode.

[Nigel Worsley]

Originally Posted by wcai_cypress

Because I am a firmware engineer, I have one more stupid question, normally, the UART module in MCU works in full-duplex mode, how to make it work in half-duplex mode.

The easiest way is not to bother!

Tie the RS485 driver chip's Driver Enable signal to the Not Receive Enable and the UART will never see the transmit data in the first place.

[sblair]

Originally Posted by Nigel Worsley

The easiest way is not to bother!

Tie the RS485 driver chip's Driver Enable signal to the Not Receive Enable and the UART will never see the transmit data in the first place.

There is a really important point here that Nigel is making. If you do have your driver chip wired such that you can see the transmit data on the receive then make sure your code ignores the receive while transmitting otherwise it is very easy to receive your own transmitted messages and parse them. (I've made that slip a couple times myself).