Registration denied after trying get connected on LTE Cat M1/NB-IoT using BG770A-Gl

IoT Modules LPWA Module
1

I’m fresh in the IoT universe, but I already had some experience getting connected using GSM modules (Quectel M95). However, I’m struggling to get connected using BG770A-GL modem, which supports LTE Cat M1/NB-IoT.

After reading some AT commands manuals, I suppose that my main problem is that I’m not fully registered yet, see the following output:

AT+CEREG?
+CEREG: 0,3

According to the datasheet, it means: Registration denied.

I’ll describe what I’ve done, and some AT command outputs, in order to give more details of my settings.

Firstly, these are the outputs that appear when I turn on the module:

RDY

+CFUN: 1

+CPIN: READY

+QUSIM: 1

+QIND: SMS DONE

+QSIMSTAT: 1,1

APP RDY

Then, I defined a PDP context:

AT+CGDCONT=1,“IP”,“smart.m2m.vivo.com.br”
AT+CGAUTH=1,1,“vivo”,“vivo”

After that, I did a network operation search:

AT+COPS=?
+COPS: (1,“VIVO”,“VIVO”,“72410”,7),(0-3),(0-2)

So, I tried to get connected manually:

AT+COPS=1,2,“72410”,8
ERROR

And I got this error.

However, there are some outputs that seem that I’m connected, see some outputs:

AT+CSQ
+CSQ: 11,99

AT+QNWINFO
+QNWINFO: “eMTC”,“72410”,“LTE BAND 3”,1750

AT+QCSQ
+QCSQ: “eMTC”,-88,-117,85,-16

But, when I try to run the ping, I got this:

AT+QPING=1,“8.8.8.8”
OK

+QPING: 569

Another weird thing is: when I try to activate a PDP context, I got error:

AT+CGACT=1,1
ERROR

AT+CGACT?
+CGACT: 1,0
+CGACT: 2,0
+CGACT: 3,0
+CGACT: 4,0
+CGACT: 5,0
+CGACT: 6,0
+CGACT: 7,0
+CGACT: 8,0
+CGACT: 9,0
+CGACT: 10,0
+CGACT: 11,0
+CGACT: 12,0
+CGACT: 13,0
+CGACT: 14,0
+CGACT: 15,0

Important: I already confirmed the APN network and user/pass with my internet provider.

Finally, I’m not sure what I need to do, if I’m missing something, so I would like to have help on it.

2

Hi
According to the query result of your AT+QCSQ, your current network signal is very weak. Please check whether the antenna is really connected and try again in another environment with good network signal.
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Select the number 7 instead of 8 if you want to configure eMTC on the BG770A-GL module.
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BR
Tabor

3

Which values on AT+QCSQ commands I should have as a minimum to establish a connection?

Besides that, what I’m thinking really weird, is that I cannot activate the PDP context, every time that I try, I get ERROR instantaneously. Since I need to have authentication to get connected, and assuming that I’ll only have it after active a PDP context, it might be the reason why I couldn’t get connected, and getting Registration denied on AT+CEREG?.

Shouldn’t I need to activate the PDP context to get connected? I think that I should be able to activate a PDP context even with a low signal.

Finally, could you give the link of the datasheet that you are looking at? Because in my source, it seems that I need to put parameter 8 for Cat-M1 and 9 for NB-IoT networks, on AT+COPS command.

4

Hi,
Could you please send me the email? I will send relevant documents to you.
The minimum access RSRP need to be viewed by capturing logs. The PDP problem may be caused by not registering on the network. Have you checked whether your sim card supports CATM or whether your sim card is overdue?

5

I’ll try to get a SIM for other provider to check this possibility. Anyway, there’s a way to ensure that my sim supports CATM and is not overdue with AT commands?

6

Relevant documents have been sent to you by email, please check.