How to know if connected with GSM or CAT-M1/NB-IoT?

Connectivity LTE Cat-M1 & NB-IoT
1

Hello:

I’m using a SIM7000A modem which supports GSM/CAT-M1/NB-IoT. I’m able to connect to the Network but I’'m not sure if I’m used GSM or LTE (Cat-M1/NB-IoT)… How can I know this and also, is there something I should select through an AT command?

Thanks
Gus

2

Hi Gus,

We produce a device that uses the SIM7000A and it’s only a CAT-M!/NB-IoT device - it doesn’t have GSM fallback. You need the SIM7000G for that.

If you issue the AT+CPSI command it will tell you the carrier and also the radio technology and many other useful data used to communicate. I find it’s a great command to log for debug.

+CPSI: LTE CAT-M1,Online,311-480,0x7F11,32573699,374,EUTRAN-BAND13,5230,3,3,-16,-107,-74,12

3

Thanks, rmontrose.

I tried AT+CPSI but I get an ERROR
Also, I couldn’t find it in the AT Command Manual v1.00 for SIM7000 Series

Please see log;
AT+COPS?
+COPS: 0,0,“AT&T Jsy Tel”,8

OK
AT+CGATT?
+CGATT: 1

OK
AT+CIFSR
ERROR
AT+CIICR
ERROR
AT+CSTT=“hologram”
OK
AT+CIICR
OK
AT+CIFSR
10.52.147.203
AT
OK
AT+CPSI
ERROR

If there any previous condition to fulfill before executing this command?

Thanks
Gus

4

Hi Gus,
Sorry I just saw your reply now. What firmware version are you using of the SIM7000A? (AT+CGMR) We’re using B03 and B04 and the AT commands in SIM7000 Series_AT Command Manual_V1.05 are supported. You can find software on the web to upgrade your modem firmware using the USB port on the modem.

Below is a copy of one of our sessions where we send data and get a response back from the server. We loop until we get a CSQ of < 31 (there’s a bug in the 7000 firmware where a CSQ of 31 means it’s still connecting to the base station). Then we verify we’re registered (a 1 or 5), then we get the base station info using the AT+CPSI command, open the socket and send/receive the data. I hope this helps!

RDY
+CFUN: 1
+CPIN: READY
SMS Ready
ATE0
OK
AT+CSTT=“Hologram”
OK
AT+CSQ
+CSQ: 99,99
OK
AT+CSQ
+CSQ: 17,99
OK
AT+CGREG?
+CGREG: 0,5
OK
AT+CPSI?
+CPSI: LTE CAT-M1,Online,310-410,0x3D84,56866834,243,EUTRAN-BAND12,5110,3,3,-20,-117,-80,5
OK
AT+GSN
865235030125443
OK
AT+CIICR
OK
AT+CIFSR
10.52.15.74
AT+CIPSTART=“TCP”,“nnn.nnn.nnn.nnn”,“pppp”
OK
CONNECT OK
AT+CIPSEND=100

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
SEND OK
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
AT+CIPCLOSE=1
CLOSE OK

5

Hello Rod:

I got the new modems (firmware B04) and the command you mentioned worked fine. Thanks for that.

I still have a question, if you don’t mind to answer;

  • I’m a little bit confused about how to command the modem in 3G vs CAT-M1/NB-IoT.

I see in your code you are using following commands to bring up wireless connection;

AT+CSTT=“Hologram”

AT+CIICR

AT+CIFSR (get IP)

and then start TCP connection, etc.

I though those commands would only apply to 3G networks… as I saw other people using;

AT+CNACT=1,“hologram”

AT+CNACT?

so I though the above ones were for CAT-M1 while the ones you described were for 3G, but it seems they can also be used in CAT-M1 as you are using this network.

So what is the difference? Which should we use? As a side note, I’m planning to use MQTT commands instead of TCP, so no sure if this makes a difference.

Thanks a lot for your support.

Regards;

Gus