[hvalentim]

I can't agree. I have an RX test unit, built with an Arduino with the CH340 chipset running CumulusMX for weeks in a PI B+ without any major problem.

Yes. With Cumulus (Mono) it runs in Linux in general flawlessly. I think they may be thinking about other stuff.

I must say than it communicates via minicom pretty well too. So the specific reason for it not to work with Weewx (Python) is enigmatic. But it should lie in the lack of consistency of the CH341.KO driver. For instance here you will find someone reporting a problem related with pyserial not initiating the serial port speed like minicom.

I tested it recently, and can confirm that the anti auto-reset circuit with the C3 capacitor, also work with Arduinos with the FTDI chipset.

Great. That seems to be the way for me to go.