Problem with BM806U-E1 / DWR-921 C3


I was using OpenWRT in many DWR-921 rel C3 without issue.
We received some units which seems to be Polish (language on the box and system language) for which I was unable to made the wwan working. Whatever the configuration.
Error is : Network registration failed, registration timeout reached
Curiously, typing this errors sends me to... polish forums... :face_with_raised_eyebrow:

I tried to make comparison with a working device and a non working one.

WWAN module looks exactly the same on both devices. It's a BM806U-E1.

I tried to switch the WWAN module, And it solved the issue : this mean that taking the WWAN module from a working router, and placing it an the non-working router made the non-working router to work normally.

using ATI AT commands ont both module send the same result
Manufacturer: BroadMobi
Model: BM806C
Revision: M1.2.0_E1.0.1_A1.1.8
IMEI: xxxxxxxxxx

Have you any clue? Is it possible to upgrade the module firmware?

Note that with Stock firmware these router were not working initially. It was necessary to upgrade to a new stock firmware (3.015) solve the issue and the router were working correctly.
I tried to update to OpenWRT AFTER the upgrade, but this made no difference.

Sim locked?

No, this can't be a SIM or configuration issue, I only change the wwan module to make it working or not.

This is also not a faulty wwan module since the DWR is working with stock firmware (but need an upgrade)

Not saying it's the sim, but the module that's locked.

Tried to put a non working BM806C in a previously working router?

Not sure i follow the story after you updated the firmware, did the non working units start to work?

This is all the tests I have done.

OWRT + polish motherboard + polish BM806C = not working
OWRT + classic motherboard + classic BM806C = working
OWRT + polish motherboard + classic BM806C = working
OWRT + classic motherboard + polish BM806C = not working
Stock initial firmware V? + polish motherboard + polish BM806C = not working (not sure if it was related)
Stock firmware V3.015 + polish motherboard + polish BM806C = working

OK, this is total madness.

I finally success to connect sending multiple AT command, including

Which I think is the good one.

I hard-rebooted the router to find the exact command which solved the issue ... but the router now works perfectly... (No need for AT commands, instant connection) :crazy_face:

So I opened another polish router, taking the wwan card to put it back on my router...

I get back the same Error ( "Network registration failed, registration timeout reached")

So I tried to get the APN configuration

+CGDCONT: 1,"IP","","",0,0                                                                                                                                   

I have no idea where does the "" APN come from, apart that I'm based in France.

This is my configuration, APN is correcly setted :


So I know how to solve the issue, but really think there is a bug somewhere.

Here are all the AT commands I've tried before the connection went UP

+CSQ: 14,99

+CREG: 0,1

+COPS: 0,0,"ST Mobile",2

+CGATT: 1                                                                                                                                                                   
+CGDCONT: 1,"IP","","",0,0                                                                                                                                   

So I assume that

  • polish module don't have the good APN associated with the SIM card by default : instead of orange.
  • OpenWRT don't change the APN correctly.

I was able to reproduce the "polish" module bug with classic module, setting a wrong APN with AT commands.

OWRT not changing the APN is probably linked to this bug :