BG77 - Can communicate via USB, but not UART/ serial

Hi there,

I have a BG77 (on a Wisblock RAK5860 module) which I am able to communicate with and configure using Qnavigator by connecting my PC directly to it via USB.

However my microcontroller can’t seem to communicate with the BG77 via UART/serial. I uploaded the arduino sketch to the microcontroller which sends the BG77 AT commands, but it never receives any responses. Even when I send an ATI command via the arduino serial monitor I get no response. The sketch on the microcontroller is running fine.

Any idea what the problem could be?

I tried changing the URC_port setting to uart1 but did not fix the problem. The firmware on the BG77 is BG77LAR02A04.


You probably should ask for support on RAK forum. I don’t have access to your board but here are some general ideas:

  1. Arduino usually works at 5V and some works at 3.3V but the UART interface of BG77 is 1.8V which requires level translator
  2. Arduino TX & RX should connect to BG77 RX & TX respectively
  3. AT commands shall end with a carriage return
  4. Make sure the UART port is the main UART but not Debug or GNSS UART
  5. Default UART setting is 115200 8N1

Good luck.

sorry , here is quectel forum, thanks for your understanding