I have a air quality measuring device with an usb interface. It uses a ch340 chip to communicate. I'd like to connect to this device using a NodeMDU ESP8266. The ch340 chip is connected to the main board of the device on a disconnectable add-on pcb (together with some other functionality). When I remove it and interface with the UART directly it works. I, however don't want to lose the functionality of the add-on PCB. I tried soldering wires to the G, Tx, Rx pins of the ch340 chip, but this does not seem to work. Any advice? Is it even possible to connect to an UART with two devices this way?
Thanks for any help and best regards.