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nRF9160 connected yet not connected

Lukas Kuhs

I'm sorry, I don't know how this is reproduceable.

Yesterday and today my connection does not work. Sometimes. Yesterday it was OK early in the morning and in the afternoon. Today it was OK until the afternoon.

I did not change the setup, just rebooting from time to time and flashing new firmware, but anything else is fine.

Is it my firmware or the "new" changes? No, yesterday I flashed an old image and it stayed in error state.

Is it the SIM card? My 1nce SIM card is active and still enough volume remaining.

Is it the location? No, yesterday I was in a different location than today.

Powering off (for some seconds without VCC) the DK did not help, changing to another 1nce SIM did not help, changing to an iBasis SIM did not help...

I digged a little bit deeper into it, enabling more debug prints...

*** Booting Zephyr OS build v2.6.99-ncs1  ***
LTE_LC_EVT_MODEM_SLEEP_ENTER:	Modem sleep enter: type=4=LTE_LC_MODEM_SLEEP_FLIGHT_MODE, time=-1
LTE_LC_EVT_MODEM_SLEEP_EXIT: 	Modem sleep exit: type=4=LTE_LC_MODEM_SLEEP_FLIGHT_MODE, time=0
LTE_LC_EVT_CELL_UPDATE: 		LTE cell changed: mcc=0, mnc=0, id=31364867, tac=26553, earfcn=0, timing_advance=0, measurement_time=0, phys_cell_id=0, rsrp=0, rsrq=0
LTE_LC_EVT_LTE_MODE_UPDATE: 	LTE mode changed: mode=7=LTEM
LTE_LC_EVT_RRC_UPDATE:			RRC mode=Connected
LTE_LC_EVT_NW_REG_STATUS:		Network registration status: Connected - roaming
LTE_LC_EVT_PSM_UPDATE:			PSM parameter update: TAU=3600, ActiveTime=-1



AT+CGMI:    	Nordic Semiconductor ASA
AT+CGMM:        nRF9160-SICA
AT+CGMR:        mfw_nrf9160_1.3.0
AT%SHORTSWVER:  nrf9160_1.3.0
AT%HWVERSION:   nRF9160 SICA BQA
AT%XNETTIME?:  	1
AT%XCBAND=?:  	%XCBAND: (1,2,3,4,5,8,12,13,18,19,20,25,26,28,66)
AT%XBANDLOCK?:  "",""
AT+CIND=?: 		+CIND: ("service",(0,1)),("roam",(0,1)),("message",(0,1))
AT+CIND?:   	0,0,0
AT%XOPCONF?:   	1
AT+CEDRXS=?:   	+CEDRXS: (0-3),(4-5),("0000"-"1111")
AT+CEDRXS?:   	
AT+CESQ:     	99,99,255,255,15,27 => rsrq=-12.000000dB rsrp=-113dBm
AT+CEINFO?:  	0,1,C,8,1,-114,0 => rsrp=-114dBm cinr=0dBm
AT%XMONITOR: 	5,"","","26201","67B9",7,3,"01DE9703",333,1444,27,25,"","11100000","00000110","01001001" => Registered, roaming === mcc=262 mnc=1 tac=0x67b9 act=LTE-M (E-UTRAN WB-S1) band=3 cellid=31364867, physcellid=333 earfcn=1444 rsrp=-113dBm snr=1dB
AT+COPS?:    	0,2,"26201",7



... IP DNS resolution possible...
... sending data possible, but socket unstable
... reeiving data fails



LTE_LC_EVT_RRC_UPDATE:			RRC mode=Idle
LTE_LC_EVT_CELL_UPDATE: 		LTE cell changed: mcc=0, mnc=0, id=30581005, tac=26553, earfcn=0, timing_advance=0, measurement_time=0, phys_cell_id=0, rsrp=0, rsrq=0

As can be seen, connection seems OK at first glance, yet MCC and MNC are both 0 in some of the queries. I have never seen this before.

Connection quality is not perfect, but yesterday I had values about 10-20dB worse and it still worked perfectly.

What else should I do to find out the problem?

What can I query to make the connection good again?

This is the modem trace:

trace-2021-10-29T15-49-39.724Z.bin

I'm glad for any help.

  • +1

    Hello Lukas,

    Its good to hear that your main problem is fixed.

    Here are the answers of your remaining questions:-

    * Which queries do You recommend to find out connection quality?

    For finding out connection quality you can use AT+CSCQ command (Nordic Semiconductor Infocenter) which shows the Reference Signal Received Quality (RSRQ) and Reference Signal Received Power (RSRP).  

    * What can I query to try to renew the connection, change operator or somehow get a connection? 

     You can write AT+COPS selects a Public Land Mobile Network(PLMN) manually. It reads and searches the current mobile network (Nordic Semiconductor Infocenter). We recommend to left it on automatic selection. 

    Regarding Debug print : I think it may not be an error as you are trying to read a field in a struct that isn't used, and thinking the invalid value in the unused field is a problem. struct lte_lc_evt is used only in the tac fields and id fields in the cell struct. Therefore, when you get the CELL-UPDATE event only these two parameter are set with value. Others are zero.   (See again- number 4 line of your debug log).  You can look at this link : https://github.com/nrfconnect/sdk-nrf/blob/main/include/modem/lte_lc.h#L179 

    Hope it helps.

    BR

    Kazi Afroza Sultana

     

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