How to communicate with EG25-G over USB to TTL connected to main UART and UART reference code for MCU integration


I have a EG25-G EXVIST testboard with USB and TTL i/f (4G LTE USB Dongle in Mexico, Kuwait, Italy - EXVIST Official Store)

I’m successfully able to connect and send AT commands via /dev/ttyUSB2 when I connect over USB directly. However, I would like to integrate the board with an MCU and will need to use the UART interface for AT commands. To test if the TTL works, I used a FTDI USB to TTL cable to connect the testboard’s TTL over a serial USB cable and tried to send basic AT commands over minicom.
However, I do not get any response from the device. Am I missing something here, as I understand the main UART is for AT commands and should be straightforward.

  • I used the default baudrate of 115200 for the USB to TTL cable connection over minicom that is detected as /dev/ttyUSB0
  • I do not receive any response from the device for the basic commands like AT or ATI.

Do i need a special driver to start using the testboard via the UART? instead of USB. Also, i would like to do the UART development for AT interface for the MCU, where can I find the reference code for the same?

Anyhelp is much appreciated. Thank you!

Got it to work using a simple UART program like screen instead of minicom. I think minicom still tries to use the tty as as USB modem instead of a direct UART communication.

Is there any reference code for UART communication driver with the the modem. If so, where can I find the same?

You can refer to the following hardware design manual, directly connect the flying wire from the UART pin on the module, and connect it to TTL to test the UART function
Quectel_EG25-G_Hardware_Design_V1.4.pdf (1.3 MB)

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