8-second delay observed between successive $GPGGA or $GPRMC sentences


I’ve encountered an issue with the NMEA sentences I’m receiving from my Quectel module.

Problem: When I read the NMEA sentences, I observe a consistent delay of 8 seconds between two successive $GPGGA or $GPRMC sentences. This delay is unexpected, as the timestamps within the NMEA sentences themselves suggest they should be generated 1 second apart. For example:

  • The first $GPGGA message is timestamped at 075623.00.
  • The second $GPGGA message is timestamped at 075624.00.

This implies a 1-second interval between the messages based on their timestamps. However, in practice, I’m seeing them with a 8-second delay when reading them via Python’s serial library.

I’ve double-checked my Python code and the serial communication setup, and there doesn’t seem to be any issue on that end that could introduce such a delay.


  • Quectel module configuration:
    Sixfab Raspberry Pi 3G/4G & LTE Base HAT
    EG25-G Mini PCIe.
  • Using Python with the serial library for communication.
    portwrite = “/dev/ttyUSB2”
    port = “/dev/ttyUSB1”

serw = serial.Serial(portwrite, baudrate=115200, timeout=1, rtscts=True, dsrdtr=True)
ser = serial.Serial(port, baudrate=115200, timeout=0.5, rtscts=True, dsrdtr=True)


45.20855215 5.760656866666 232.3 0 2023-09-17T07:53:42.056269Z
45.208552116666 5.76065685 232.3 0 2023-09-17T07:53:50.130236Z
45.2085521 5.76065685 232.3 0 2023-09-17T07:53:58.196584Z
45.208552116666 5.760656816666 232.3 0 2023-09-17T07:54:06.269056Z
45.208552116666 5.760656783333 232.3 0 2023-09-17T07:54:14.353320Z
45.208552116666 5.76065675 232.3 0 2023-09-17T07:54:22.421426Z
45.208552116666 5.760656733333 232.3 0 2023-09-17T07:54:30.480493Z
45.208552116666 5.760656716666 232.3 0 2023-09-17T07:54:38.549212Z
45.208552133333 5.760656633333 232.2 0 2023-09-17T07:54:47.639518Z

Has anyone else encountered a similar issue? Any suggestions on what could be causing this discrepancy and how to fix it?

Thank you in advance for your insights!