Problem with BM806U-E1 / DWR-921 C3

Hardware Questions and Recommendations
1

Hi,

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
+GCAP: +CGSM

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.

2

Sim locked?

3

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)

4

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?

5

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

6

OK, this is total madness.

I finally success to connect sending multiple AT command, including
AT+CGDCONT=1,"IP","orange"

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

AT+CGDCONT?                                                                                                                                                                 
+CGDCONT: 1,"IP","ofnew.fr","0.0.0.0",0,0

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

This is my configuration, APN is correcly setted :

network.wwan=interface
network.wwan.proto='wwan'
network.wwan.apn='orange'
network.wwan.pincode='0000'
network.wwan.auto='1'

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

AT+CSQ
+CSQ: 14,99

OK
AT+CREG?
+CREG: 0,1

OK
AT+CREG=1
OK
AT+COPS?
+COPS: 0,0,"ST Mobile",2

OK
AT+CGATT?
+CGATT: 1                                                                                                                                                                   
                                                                                                                                                                            
OK                                                                                                                                                                          
AT+CGDCONT?                                                                                                                                                                 
+CGDCONT: 1,"IP","ofnew.fr","0.0.0.0",0,0                                                                                                                                   
                                                                                                                                                                            
OK                                                                                                                                                                          
AT+CGDCONT=1,"IP","orange"                                                                                                                                                  
OK
7

So I assume that

  • polish module don't have the good APN associated with the SIM card by default : ofnew.fr instead of orange.
  • OpenWRT don't change the APN correctly.
8

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 : https://github.com/openwrt/openwrt/issues/6295