Using mikroe "LTE IoT Click" aka u-blox SARA-R410M-02B with native serial UART

Tue Apr 27 15:38:32 UTC 2021

Hello,

Am Mittwoch, 24. März 2021, 17:07:44 CEST schrieb Alexander Dahl:
> That looks promising, I'll see if I can register to the network if the
> correct SIM cards arrive.

I got the SIM cards now. Those are by German Telekom for business customers. 
(German FAQ here: [1])

Recap: the modem is a u-blox SARA-R410M-02B, and it's connected through the 
serial UART only (NOT through USB), meaning only two pins, txd and rxd, 
classical uart, 115200 baud, /dev/ttyAT2.

I got ModemManager (1.16.4) to recognize the modem and this works:

    mmcli -m 1 -e
    mmcli -m 1 --simple-connect='apn=iot.telekom.net'
    mmcli -m 1

The modem is shown in connected state with reasonable operator id 26201 and 
signal quality 80%. Debug log even shows an IP address (in 10.0.0.0/8), the 
same as listed in the web portal of Deutsche Telekom, which also confirms 
modem/sim are registered to the network. So far so good.

However there's no network device listed, `ip addr show` shows only ethernet 
and loopback.

In the hope NetworkManager (1.30.4) would create that device for me, I tried 
to get a connection with NetworkManager like this:

    nmcli connection add type gsm
    nmcli connection modify gsm apn iot.telekom.net

And:

    root at DistroKit:~ nmcli -a con up gsm
    Error: Connection activation failed: The base network connection was 
interrupted
    Hint: use 'journalctl -xe NM_CONNECTION=0b5580ba-33f9-49f6-
bd17-33c14d38bb97 + NM_DEVICE=ttyAT2' to get more details.

I had NetworkManager monitor on a second console in parallel, which gave this:

    root at DistroKit:~ nmcli m
    ttyAT2: deactivating
    ttyAT2: disconnected
    ttyAT2: using connection 'gsm'
    ttyAT2: connecting (prepare)
    ttyAT2: unmanaged
    ttyAT2: device removed

Now the interesting part, `journalctl -u ModemManager`:

```
Apr 27 14:49:46 DistroKit systemd[1]: Starting ModemManager.service...
Apr 27 14:49:47 DistroKit ModemManager[416]: <info>  ModemManager (version 
1.16.4) starting in system bus...
Apr 27 14:49:47 DistroKit systemd[1]: Started ModemManager.service.
Apr 27 14:49:50 DistroKit ModemManager[416]: <info>  [base-manager] couldn't 
check support for device '/sys/devices/platform/ahb/ahb:apb/
f8008000.ethernet': not supported by any plugin
Apr 27 14:50:05 DistroKit ModemManager[416]: <info>  [device /sys/devices/
platform/ahb/ahb:apb/f8024000.serial/atmel_usart_serial.1.auto] creating modem 
with plugin 'generic' and '1' ports
Apr 27 14:50:05 DistroKit ModemManager[416]: <warn>  [plugin/generic] could 
not grab port ttyAT2: Cannot add port 'tty/ttyAT2', unhandled port type
Apr 27 14:50:05 DistroKit ModemManager[416]: <warn>  [base-manager] couldn't 
create modem for device '/sys/devices/platform/ahb/ahb:apb/f8024000.serial/
atmel_usart_serial.1.auto': Failed to fi>
Apr 27 14:50:10 DistroKit ModemManager[416]: <info>  [base-manager] couldn't 
check support for device '/sys/devices/platform/ahb/ahb:apb/
f8008000.ethernet': not supported by any plugin
Apr 27 14:50:25 DistroKit ModemManager[416]: <info>  [device /sys/devices/
platform/ahb/ahb:apb/f8024000.serial/atmel_usart_serial.1.auto] creating modem 
with plugin 'generic' and '1' ports
Apr 27 14:50:25 DistroKit ModemManager[416]: <warn>  [plugin/generic] could 
not grab port ttyAT2: Cannot add port 'tty/ttyAT2', unhandled port type
Apr 27 14:50:25 DistroKit ModemManager[416]: <warn>  [base-manager] couldn't 
create modem for device '/sys/devices/platform/ahb/ahb:apb/f8024000.serial/
atmel_usart_serial.1.auto': Failed to fi>
Apr 27 14:50:50 DistroKit ModemManager[416]: <info>  [base-manager] couldn't 
check support for device '/sys/devices/platform/ahb/ahb:apb/
f8008000.ethernet': not supported by any plugin
Apr 27 14:50:58 DistroKit ModemManager[416]: <info>  [device /sys/devices/
platform/ahb/ahb:apb/f8024000.serial/atmel_usart_serial.1.auto] creating modem 
with plugin 'u-blox' and '1' ports
Apr 27 14:50:59 DistroKit ModemManager[416]: <info>  [base-manager] modem for 
device '/sys/devices/platform/ahb/ahb:apb/f8024000.serial/atmel_usart_serial.
1.auto' successfully created
Apr 27 14:50:59 DistroKit ModemManager[416]: <warn>  [modem2] (u-blox) 
unexpected AcT value: 7
Apr 27 14:50:59 DistroKit ModemManager[416]: <warn>  [modem2] (u-blox) 
unexpected AcT value: 8
Apr 27 14:50:59 DistroKit ModemManager[416]: <warn>  [modem2] couldn't load 
supported modes: No combinations built from +URAT=? response
Apr 27 14:50:59 DistroKit ModemManager[416]: <warn>  [modem2] couldn't load 
unlock retries: Unknown error
Apr 27 14:50:59 DistroKit ModemManager[416]: <warn>  [modem2/sim0] couldn't 
load list of emergency numbers: uninitialized emergency numbers list
Apr 27 14:50:59 DistroKit ModemManager[416]: <warn>  [modem2] couldn't load 
list of own numbers: Invalid characters in dial string
Apr 27 14:50:59 DistroKit ModemManager[416]: <warn>  [modem2] couldn't load 
current bands: Unknown error
Apr 27 14:50:59 DistroKit ModemManager[416]: <info>  [modem2] state changed 
(unknown -> disabled)
Apr 27 14:50:59 DistroKit ModemManager[416]: <info>  [modem2] state changed 
(disabled -> enabling)
Apr 27 14:51:00 DistroKit ModemManager[416]: <info>  [modem2] simple connect 
started...
Apr 27 14:51:00 DistroKit ModemManager[416]: <info>  [modem2] simple connect 
state (4/8): wait to get fully enabled
Apr 27 14:51:00 DistroKit ModemManager[416]: <info>  [modem2] 3GPP 
registration state changed (unknown -> idle)
Apr 27 14:51:00 DistroKit ModemManager[416]: <info>  [modem2] state changed 
(enabling -> enabled)
Apr 27 14:51:00 DistroKit ModemManager[416]: <info>  [modem2] simple connect 
state (5/8): register
Apr 27 14:51:00 DistroKit ModemManager[416]: <info>  [modem2] 3GPP 
registration state changed (idle -> registering)
Apr 27 14:51:00 DistroKit ModemManager[416]: <info>  [modem2] 3GPP 
registration state changed (registering -> roaming)
Apr 27 14:51:00 DistroKit ModemManager[416]: <info>  [modem2] state changed 
(enabled -> registered)
Apr 27 14:51:00 DistroKit ModemManager[416]: <info>  [modem2] simple connect 
state (6/8): bearer
Apr 27 14:51:01 DistroKit ModemManager[416]: <info>  [modem2] simple connect 
state (7/8): connect
Apr 27 14:51:01 DistroKit ModemManager[416]: <info>  [modem2] state changed 
(registered -> connecting)
Apr 27 14:51:01 DistroKit ModemManager[416]: <info>  [modem2] state changed 
(connecting -> connected)
Apr 27 14:51:01 DistroKit ModemManager[416]: <info>  [modem2] simple connect 
state (8/8): all done
Apr 27 14:51:06 DistroKit ModemManager[416]: <warn>  [modem2] couldn't load 
network timezone from the current network
Apr 27 14:51:12 DistroKit ModemManager[416]: <info>  [base-manager] couldn't 
check support for device '/sys/devices/platform/ahb/ahb:apb/
f8008000.ethernet': not supported by any plugin
Apr 27 14:55:36 DistroKit ModemManager[416]: <info>  [modem2] state changed 
(connected -> disconnecting)
Apr 27 14:55:45 DistroKit ModemManager[416]: <warn>  [modem2] port ttyAT2 
timed out 2 consecutive times
Apr 27 14:55:48 DistroKit ModemManager[416]: <warn>  [modem2] port ttyAT2 
timed out 3 consecutive times
Apr 27 14:55:51 DistroKit ModemManager[416]: <warn>  [modem2] port ttyAT2 
timed out 4 consecutive times
Apr 27 14:55:54 DistroKit ModemManager[416]: <warn>  [modem2] port ttyAT2 
timed out 5 consecutive times
Apr 27 14:56:04 DistroKit ModemManager[416]: <info>  [modem2] state changed 
(disconnecting -> registered)
Apr 27 14:56:04 DistroKit ModemManager[416]: <info>  [modem2/bearer0] 
connection #1 finished: duration 302s, tx: 0 bytes, rx :0 bytes
Apr 27 14:56:04 DistroKit ModemManager[416]: <warn>  [modem2] port ttyAT2 
timed out 6 consecutive times
Apr 27 14:56:04 DistroKit ModemManager[416]: <info>  [modem2] simple connect 
started...
Apr 27 14:56:04 DistroKit ModemManager[416]: <info>  [modem2] simple connect 
state (4/8): wait to get fully enabled
Apr 27 14:56:04 DistroKit ModemManager[416]: <info>  [modem2] simple connect 
state (5/8): register
Apr 27 14:56:04 DistroKit ModemManager[416]: <info>  [modem2] simple connect 
state (6/8): bearer
Apr 27 14:56:04 DistroKit ModemManager[416]: <info>  [modem2] simple connect 
state (7/8): connect
Apr 27 14:56:04 DistroKit ModemManager[416]: <info>  [modem2] state changed 
(registered -> connecting)
Apr 27 14:56:09 DistroKit ModemManager[416]: <warn>  [modem2] port ttyAT2 
timed out 7 consecutive times
Apr 27 14:56:12 DistroKit ModemManager[416]: <warn>  [modem2] port ttyAT2 
timed out 8 consecutive times
Apr 27 14:56:15 DistroKit ModemManager[416]: <warn>  [modem2] port ttyAT2 
timed out 9 consecutive times
Apr 27 14:56:18 DistroKit ModemManager[416]: <warn>  [modem2/bearer0] couldn't 
initialize context: Serial command timed out
Apr 27 14:56:18 DistroKit ModemManager[416]: <warn>  [modem2/bearer0] 
connection attempt #2 failed: Serial command timed out
Apr 27 14:56:18 DistroKit ModemManager[416]: <info>  [modem2] state changed 
(connecting -> registered)
Apr 27 14:56:18 DistroKit ModemManager[416]: <info>  [modem2/bearer0] 
connection #2 finished: duration 0s, tx: 0 bytes, rx :0 bytes
Apr 27 14:56:18 DistroKit ModemManager[416]: <error> [modem2] port ttyAT2 
timed out 10 consecutive times, marking modem as invalid
Apr 27 14:56:18 DistroKit ModemManager[416]: <info>  [modem2] simple connect 
started...
Apr 27 14:56:18 DistroKit ModemManager[416]: <info>  [modem2] simple connect 
state (4/8): wait to get fully enabled
Apr 27 14:56:18 DistroKit ModemManager[416]: <info>  [modem2] simple connect 
state (5/8): register
Apr 27 14:56:18 DistroKit ModemManager[416]: <info>  [modem2] simple connect 
state (6/8): bearer
Apr 27 14:56:18 DistroKit ModemManager[416]: <info>  [modem2] simple connect 
state (7/8): connect
Apr 27 14:56:18 DistroKit ModemManager[416]: <info>  [modem2] state changed 
(registered -> connecting)
Apr 27 14:56:18 DistroKit ModemManager[416]: <warn>  [modem2/bearer1] 
connection attempt #1 failed: Operation was cancelled
Apr 27 14:56:18 DistroKit ModemManager[416]: <info>  [modem2/bearer1] 
connection #1 finished: duration 0s, tx: 0 bytes, rx :0 bytes
```

From my naïve understanding, commands and data stream have to be multiplexed 
over the same serial uart, right? Is it a problem of ModemManager or 
NetworkManager?

I have not much experience with these kinds of devices, so each hint to 
proceed would be helpful. I can build and run MM and NM from source, even most 
recent master. I can provide debug logs. I would provide patches, but 
currently I don't even know where to start. O:-)

Is there a way to get this modem running on Linux over that single UART at 
all?

Greets
Alex

[1] https://business-portal-smart-connect.telekom.de/tdg-shop/faq