Raspberry Pi – couple of questions

Home Forums Forums Technical Support for the OzzMaker SARA-R5 LTE-M GPS + 10DOF Raspberry Pi – couple of questions

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    I seem to have this HAT setup and working on my headless Pi4 for my telescope mount but there’s a couple of things I can’t quite work out,

    1. Restarting the Pi with shutdown -r now results in the mux connection disappearing on reboot. /dev/pts only has 0 (when I ssh in) and ptmx on the reboot. How can I fix this? The only way I have found to get the mux back is to power down everything, which isn’t ideal! The /tmp entries are there at reboot but show as red as the links can’t be reached. Do I need to delete these at shutdown?
    2. I’ve updated the python script for python 3 (couple of small changes like the print uses brackets now) but I would like it to be able to differentiate between when the SIM card is available and when it isn’t. To get the normal GPS working with no assistance, I need to add AT+UGIND=1 to the list of commands but this isn’t needed if the SIM is available and the AssistNow connection and download works. Can the Python script be changed to realise when the AT+UGIND=1 is needed? My python skills are non-existent … running the script when the SIM card isn’t in the HAT results in the normal GPS not working (I think)




    Mark Williams

    Hi JimBob

    1. You need to start gsmMuxd on every boot. You can use the rc.local to start it.
    You also need to shut it down or kill in when rebooting the Pi. This disables the mux on both the 5G modem and the Pi itself. a simple sudo killall gsmMuxd will do.
    We are working on a guide to create a systemd file to look after all this so it is automated

    2.Even if you try assist online and you dont have a SIM in, it should still work, it will just fail to download the data and rely on normal data it receives from the satellites in the sky. AT+UGIND=1 is only used to report results. This command AT+UGPS=1,1,71 can be used to stat with local aiding only.

    Mark --OzzMaker.com --


    Hmmm … interesting. I do have gsmMuxd starting via systemd and I assume it gets closed down as part of the shutdown (or reboot) process. My simple service file is attached and started before the python script and gpsd.

    I *think* I’ve managed to change the python script to check if the SIM is present to fix question 2 … just need to check it actually works. Its working correctly without the SIM card inserted and need to check it works with the SIM and downloads the AssistNow data.



    I can see you have updated the mux setup pages to help fix the missing mux on reboot … not tried it yet but have yet another question about this board. I noticed the attached on the SparkFun guide linked here for a firmware issue with the PPS setup with the version 2.06 firmware – attached is an image of the relevant text. I assume this is an issue with your board too or has it been resolved? One of the main reason for buying this board was the A-GPS capability but I also need to use the PPS sync … if this is impossible then what can you do to resolve this?

    I purchased my board from PiHut in the UK and pretty sure they will augh if I try to return it now after the setup issues raised above.



    Regarding sparkfun’s guide, I think that may be related to the use the LED.

    We did test this in the past.. and I just tested now, it does work. The Pi can see the pin go high

    On a Pi 4 i connected the TP pin from the SARA-R5 to GPIO21 on the PI.
    I created a python script to see when this goes high;

    import RPi.GPIO as GPIO
    GPIO.setup(21, GPIO.IN)
    while True:
            if GPIO.input(21):
                    print (" high!")

    I then configured the below commands on the SARA-R5


    The python script was able to see the pin go high every second.

    Richard --OzzMaker.com --


    Hi Richard,

    Phew! Thanks for putting my mind at rest. I guess I’ll be digging out the soldering iron to attach some pins then.

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