I am attempting to connect to a personalized embedded board having a GSM module (UC20-Quectel). Initially, I aim to connect to this module through a WiFi connection to assess the GSM status and its parameters using AT commands in a command window.

I’ve only had two opportunities to have GSM module manufacturer and status (microcom -s 115200 /dev/ttyUSB3 ), then typing ATI. However, subsequent attempts to use the microcom were unsuccessful as it didn’t respond, and I couldn’t input or read anything.

Subsequently, I tried using Putty, but encountered the same lack of response.

To troubleshoot, I connected the board to my laptop via a UART cable and attempted to repeat the steps. However, I encountered the same issue with both microcom and Putty – no response, output, or error messages.

Further investigation revealed that when connecting the UART cable, two ports appeared in the device manager: COM3 and RNDIS, with an interrogation mark. When attempting to install it from the USB driver of the embedded board (Linux USB Ethernet/RNDIS Gadget), I received an error indicating that the third-party INF does not contain digital signature information.

As I am new to GSM communications modules, my questions are:

How can I establish successful communication between the GSM module (embedded board) and my computer? Is it necessary to install the RNDIS USB driver, and is it useful for both serial communication and SSH communication?

If I am on the wrong path, could someone please guide me through the necessary steps and provide documentation or tutorials to assist? I have read many AT commands and watched several video tutorials, but the connection or communication part is still unclear to me.

Thank you very much.