Half-duplex serial comms

Posted on Sat 26th, October 2024

• #1

user157904

Is there a way to enable half-duplex UART on Espruino Pico? I have a device that I communicate with using standard serial over one wire, however I am using an NPN and PNP transistor to toggle between rx/tx. I believe that STM32’s have half duplex UART capability but I’m not sure if/how this can be enabled in Espruino. It would be nice to connect the directly to the pico instead of needing additional transistors.
• #2

Gordon

Hi,

I'm afraid it's not something that I is exposed - but presumably you could just attach a signal diode (so only 0.3v drop) between the STM32 TX pin and the serial line, so it's only ever capable of pulling the signal down?

You could take a look at https://www.espruino.com/STM32+Peripherals though as it may be you can set the STM32 up as normal and then just poke a register value in the UART to enable the half duplex mode?
• #3

user157904 in reply to @Gordon

Hi Gordon,

Thanks for your response. I managed to activate half duplex mode by poking the correct register as you suggested and all seems to work as expected.

Thanks!

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