BC95-G Modem deregisters / unregisters; CEREG <stat> goes from 5 to 0

brixton · October 26, 2021, 9:23am

Hello,
I have a BC95-G which generally works fine and sends messages properly. However every now and then the CEREG value suddenly changes from 5 (registered, roaming) to 0 (not registered, not trying to be registered). And then often goes to 2 (trying to register). This happens in regions with good coverage. After that, when trying to send via UDP, the ERROR value is returned.

Does anyone have any idea what might be going on? Many thanks!

11:01:48.746 -> +NPSMR:0
11:01:48.746 -> 
11:01:50.246 -> 
11:01:51.754 -> 
11:01:53.254 -> 
11:01:54.717 -> 
11:01:54.717 -> +CEREG:0,0000,00000000,9,,,,
11:01:54.717 -> 
11:01:54.717 -> +NPSMR:1
11:01:54.717 -> 
11:01:56.230 -> 
11:01:57.737 -> 
11:01:57.737 -> +CEREG:2,2779,0191EB66,9,,,,
11:01:57.737 -> 
11:01:57.737 -> +NPSMR:0

herbert.pan-Q · October 27, 2021, 1:40am

hi,brixton:
I would like to know if you are in roaming border area, please perform AT+NUESTATS? to Confirm whether the base station cell registered by the terminal changes before and after the status change.

AT+NUESTATS

brixton · October 27, 2021, 9:21am

Hi @herbert.pan-Q,

During normal operation when CEREG “stat” = 5, I get the following:

AT+NUESTATS
11:15:31.723 -> 
 Signal power:-1106
 Total power:-929
 TX power:230
 TX time:2247
 RX time:39195
 Cell ID:26340198
 ECL:2
 SNR:-96
 EARFCN:6254
 PCI:73
 RSRQ:-209
 OPERATOR MODE:3
 CURRENT BAND:20
 
 OK

Then “stat” changed to 2 and NUESTATS becomes:

11:17:32.047 -> AT+NUESTATS
11:17:32.235 -> 
 Signal power:-1109
 Total power:-930
 TX power:230
 TX time:3048
 RX time:111400
 Cell ID:26340198
 ECL:2
 SNR:-68
 EARFCN:6254
 PCI:73
 RSRQ:-185
 OPERATOR MODE:3
 CURRENT BAND:20
 
 OK

herbert.pan-Q · October 27, 2021, 9:40am

Signal power corresponding RSRP equal to -110.9dBm,and ECL:2;RSRQ:-20.9,the signal strength is very weak,the signal is approaching the edge of the terminal access signal.return +CEREG:2 is understandable;but Roaming doesn’t show up.If you need to dig deeper, you need to grab the Log.

brixton · October 27, 2021, 11:19am

I didn’t quite understand what you meant with ‘grab the log’, so I’ve set ““AT+NLOGLEVEL=APPLICATION,VERBOSE””. However that doesn’t give any extra information.

Currently I have a MCU connected to the BC95-G via the MAIN UART connection, but to see the logs I’m guessing I’ll need to make a connection to the DEBUG UART? I’ll will do that now to create some more insight.

herbert.pan-Q · October 28, 2021, 12:57am

Download the log tool from the link：
https://quectel123-my.sharepoint.cn/:u:/g/personal/ae-fae_dom_quectel_com_cn/EeUDa37BBDxKgjvAtkcgD2MBmCDfpNi0McdvTgkxnnTZRQ?e=yWPLcC
Before capturing logs, this tool needs license authorization, and you need to provide the corresponding sequence code. I will apply for a license for you, and then this tool can be used normally.

brixton · October 28, 2021, 9:24am

Here is a log file (a few minutes of logging).

However today I’m at a different geographical location than yesterday, and the network coverage seems to be better here. And so far the CEREG “stat” value is still at 5, so I’m not sure how useful this logging information is.

debugProj1.zip (171.3 KB)

herbert.pan-Q · October 28, 2021, 9:42am

hi,brixton:
LOG analysis shows that the PLMN of the current module registered network is 204 04.Please consult the PLMN configured for the SIM card by your SIM card provider to confirm whether the SIM card is in roaming state

The current terminal does get a better signal from the base station than it did yesterday.