Quectel EC25 UART with ModemManager/NetworkManager

Technical Subjects Driver
1

Hi,

We have so far used the Quectel EC25AFA via USB with a Raspberry Pi 4 using ModemManager and NetworkManager. We’re now looking to embed the modem and use the UART interface instead of USB. We have a working UART connecting, and the modem responds correctly to AT commands on the UART. However, neither ModemManager nor NetworkManager can detect the modem.

Out hardware setup:

  • Quectel UART_RX → RPi GPIO8 (UART 4)
  • Quectel UART_TX → RPi GPIO9 (UART 4)
  • Quectel UART_CTS → RPI GPIO11
  • Quectel UART_RTS → RPI GPIO10

We’ve set the following udev rules in sudo nano /etc/udev/rules.d/99-ttyAMA4-modem.rules :

# Rule for ModemManager to handle the Quectel modem on ttyAMA4
ACTION=="add|change", SUBSYSTEM=="tty", KERNEL=="ttyAMA4",
ENV{ID_MM_CANDIDATE}="1",
ENV{ID_MM_TTY_BAUDRATE}="115200",
ENV{ID_MM_TTY_FLOW_CONTROL}="rtscts"

However, mmcli -L returns No modems found

Similarly, using NetworkManager sudo nmcli device connect ttyAMA4 returns Error: Device 'ttyAMA4' not found.

My question is: Is it possible to use the EC25 UART with ModemManager/NetworkManager? If so, is there any documentation on how to do this?

2

We have never tried that? Do you must try the ModemManager?
Or you just need to set up data connection for the rpi4.

3

I don’t think we HAVE to use ModemManager/NetworkManager. What do you recommend for data/GPS connection on RPi 4?

4

For Main uart, you can only use the PPP for data connection.

Main uart for AT and PPP data call.
Debug uart for GPS.

5

Uart might not support for ModemManager. If you have to use the ModemManager you need the USB.