SIMCOM SIM7070G UART Support

[Aleksander Morgado]

Hey

> I'm trying to configure a SIMCOM7070G modem to work with ModemManager/NetworkManager.
>
> I've observed there is already a plugin and some support, but unless I'm mistaken, it looks like the current support expects this modem to be connected via USB (4 ports provided by usb: AT cmds, data, gnss, etc).
>
> My problem is I'm using it in a board where the modem is NOT connected to the CPU via USB: The regular UART (UART1) provided by the modem is used.
>
> So far, I already have some signals of life:
>
> 1. MODEM is detected by ModemManager as Generic GSM modem: I added the following rule to /etc/udev/rules.d/ and works fine:
>
> ACTION!="add|change|move|bind", GOTO="mm_whitelist_end"
> KERNEL=="ttyS4" ENV{ID_MM_DEVICE_PROCESS}="1"
> LABEL="mm_whitelist_end"
>

There are several things missing here.

The "simtech" plugin only expects USB modems right now. It should be
updated to have MM_PLUGIN_ALLOWED_VENDOR_STRINGS, so that after the AT
probing phase is run, ModemManager tries to guess the modem vendor
based on the given string. Once that works, the simtech plugin will
take control of your modem, with the simcom-specific features if any
needed.

Then given you're using a pure RS232 port, please note that you should
explicitly configure how the TTY is supposed to work, in particular,
you need to define ID_MM_TTY_BAUDRATE and ID_MM_TTY_FLOW_CONTROL
explicitly. If your modem works fine AT-control wise, then probably
the default baudrate MM uses was good (57600), but you should better
explicitly define it. And if the data connection over PPP is not
working as expected as in your case, it may indeed because of the
missing ID_MM_TTY_FLOW_CONTROL (either "none", "xon-xoff" or
"rts-cts").


> 2. I Added a gsm connection to set the APN: (iot.t-mobile.nl)
> I can see in ModemManager logs how it exchanges a lot of AT commands, etc to finally launch PPP. And this is where I'm stuck.
> After ppp gets launched, if I check the status of the connection using nmcli I can see it is "getting ip address" and stays like that forever.
>
> I'm attaching the whole log of ModemManager (debug mode). Not sure what I'm missing/doing wrong.
>

You're controlling the connection through NetworkManager, though,
right? Can you reproduce it and gather both MM and NM debug logs? See
https://modemmanager.org/docs/modemmanager/debugging/#daemon-debug-logs

-- 
Aleksander