RM520n-GL Works in ECM mode but if signal is lost, it wont reconnect!

Hey!
When I run the modem in RNDIS mode, if I remove the sim card, and re insert it the modem will re-establish the connection. But in ECM mode I need to reboot the modem for it to detect the sim being inserted. Is this normal?

Also and this is my big problem! If in ECM mode if I drop the cellular connection cause of reception it will never reconnect again when signal is resumed. Only way I have found to get the modem to reconnect is to do a full restart of the modem.

Modem is connected to a Waveshare usb-to-m.2-b-key board on a Orange Pi 5 Plus running ubuntu and the custom software needs the ECM mode to see the modem. In RNDIS the module shows up as a WWAN device and wont work in the bonder.

Any help would be much appriciated!

Thanks!

Dear @JohannesSchander
Please confirm the driver is correct.
The ECM driver is Kernel built-in.
lsusb -t

Does this look correct?

Hi Johannes!
I have exactly the same problem, how did you solve it?

Manually entering APN did it for me :+1:

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Thanks for this info. I’ve been using ECM for its stability but i didn’t input any apn so that’s why it doesn’t reconnect sometimes.

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Yes this is quite likely! My application did not allow IPv6 adresses and that was a second “strange” bug I found. But you can limit it to IPv4 in the APN command.

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Thank you for your answer :slight_smile:
Have you only set the 1 to ipv4 and left the rest on IPV4V6?

AT+CGDCONT?

+CGDCONT: 1,"IP","myapn.com","0.0.0.0",0,0,0,0,,,,,,,,,"",,,,0
+CGDCONT: 2,"IPV4V6","ims","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0,,,,,,,,,"",,,,0
+CGDCONT: 3,"IPV4V6","hos","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0,,,,,,,,,"",,,,0
+CGDCONT: 4,"IPV4V6","sos","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,1,,,,,,,,,"",,,,0

Yes thats how I do it.
I will admit not being 100% sure if the 2,3 4 etc matters. IIRC the IMS etc are just emercency service stuff to e.g call 911.