@FransvanHoogstraten. I can do that for you. Can you please enable support access to the test device I used earlier?
@aleksander0m, thanks a lot for jumping in here 
Ah, it is actually still enabled (I used a non-support account to check earlier on). Just let me know and I can handle this.
No need, the udev rules are read line by line, and the 3 lines should be fine.
Run this to list tags in the device:
udevadm info -p /sys/devices/platform/soc/3f201000.serial/tty/ttyAMA0
And actually… maybe the correct rule is this one (with the longer devpath). I’m not very used to tagging non usb devices…
ACTION!="add|change|move|bind", GOTO="mm_whitelist_end"
DEVPATH=="/devices/platform/soc/3f201000.serial/tty/ttyAMA0" ENV{ID_MM_DEVICE_PROCESS}="1"
LABEL="mm_whitelist_end"
Thanks, I will try both now.
@aleksander0m, still not working unfortunately.
It needed the full path indeed. Output from udevadm:
root@eb6f6c5:/# udevadm info -p /sys/devices/platform/soc/3f201000.serial/tty/ttyAMA0
P: /devices/platform/soc/3f201000.serial/tty/ttyAMA0
N: ttyAMA0
L: 0
S: serial0
E: DEVPATH=/devices/platform/soc/3f201000.serial/tty/ttyAMA0
E: DEVNAME=/dev/ttyAMA0
E: MAJOR=204
E: MINOR=64
E: SUBSYSTEM=tty
E: USEC_INITIALIZED=5827474
E: ID_MM_CANDIDATE=1
E: ID_MM_DEVICE_PROCESS=1
E: DEVLINKS=/dev/serial0
E: TAGS=:systemd:
And a link with the debug logs from ModemManager:
Yeah I got to this point once, but then couldn’t reproduce it. So in that way, we are making progress! 
To me it would seem from the logs that MM is not able to send/receive AT commands to the modem
When I use minicom from the container to talk to ttyAMA0 though, I can send AT commands and get a response:
Welcome to minicom 2.7
OPTIONS: I18n
Compiled on Apr 22 2017, 09:14:19.
Port /dev/ttyAMA0, 13:03:50
Press CTRL-A Z for help on special keys
AT
OK
AT+CGMI
Quectel
OK
AT+CGMR
EC25EFAR06A04M4G
OK@FransvanHoogstraten I think I misconfigured now the config.json and the device does not boot anymore… I wanted to try out setting a different ID_MM_TTY_BAUDRATE, but probably forgot a quote or something. Can you please reprovision the device? Sorry for the trouble…
I should not have done it through config.json in the first place, but just create the .rules file directly (more suitable for testing)…
Done! I renamed the old config.json and reinstalled the original config.json in the boot partition.
Oh, thanks. I will try out the extra ID_MM_TTY_ options available
@FransvanHoogstraten What settings did you use for running minicom in the container? It shows offline when I try running it.
Yeah I can’t get a response from the modem myself right now, weird. Looking into it
Minicom again stopped working. I am short of ideas at this stage.
@majorz would you be able to share your findings here and with @aleksander0m?
Is MM now picking up the port? Where in the process do things go wrong?
It is the same situation as in the gist link with logs I pasted above. From what I can tell commands are sent, but no response is logged. I tried tweaking ID_MM_TTY_FLOW_CONTROL and ID_MM_TTY_BAUDRATE, but could not make a difference.
Can you give me access to the setup to check that myself?
What is your username on balena-cloud.com ?
I am trying to add you but I get the message that ‘aleksander0m’ is not a valid username there