reTerminal DM RS232 driver bug

I have encountered an issue with the reTerminal DM RS232 serial driver.

The TX & RX pins are looped back to each other as follows:-

The issue is when I output a string in one shell and read it back in another, there is some strange end-of-buffer issue where I get unlimited spurious characters at the end.

To demonstrate, I loaded two shell terminals.

In the first shell, I set the serial port to 57600, “raw” mode using:-

stty -F /dev/ttyCH343USB0 57600 raw

To confirm the settings, I then do:-

stty -F /dev/ttyCH343USB0 -a

I then display anything coming over the serial port using:-

cat < /devttyCH343USB0

In the second shell, I send the current date down the serial port using:-

date > /dev/ttyCH343USB0

Back in the first shell, the date appears plus the first two characters of the date repeated indefinitely.

Fri 10 Apr 16:44:22 BST 2026
Fr4FrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrFrF

This link is a video showing the issue … https://photos.app.goo.gl/LTV96U2WmDe7PiLr7

It is using an up-to-date install of 32bit Raspbian Bullseye.

I have finally found a fix.

The Linux driver installed by default is v1.5 and needs updating to at least v2.0 from https://github.com/WCHSoftGroup/ch343ser_linux

git clone https://github.com/WCHSoftGroup/ch343ser_linux.git
cd ch343ser_linux
make
sudo make install
reboot

Job done :partying_face:

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