Connect to Cellular Network

Mbed OS
1

Hi Everyone!

I am having trouble connecting to the cellular network. I can get the CellularContext. However, the CellularContext::connect() function just hangs and cannot connect. Am I missing something?

So far, I’ve tried:

  1. Changing different APN as my ISP (YesOptus) have multiple APN to choose from.
  2. I’ve set and reset the SIM PIN to 0000
  3. Tried Mbed-Cellular-Example and failed.
  4. Tried different Sim Card with different data plans.

My hardware:
NuMaker M263A
EC25 MiniPCIE Networking Card
And an LTE Antenna connected to EC25 MAIN Connector.

Following is my code:

int main()
{
    c_context = CellularContext::get_default_instance();


    if (c_context->connect() == NSAPI_ERROR_OK) // The programs hangs here.
    { 
        pc.printf("Connection Status: %hi\n", c_context->get_connection_status());
    }
    else 
    {
        pc.printf("Failed\n");
    }
}

This is my ISP’s APN settings:
YesOptus APN Settings

In summary:
PLMN: 50502
SIM PIN: 0000
APN : connect/connectme/yesinternet
Username: Not Set / Leave Blank
Password: Not Set /. Leave Blank

This is my mbed_app.json:

 "target_overrides": {
        "*": {
            "GENERIC_AT3GPP.provide-default": true,
            "GENERIC_AT3GPP.tx": "D1",
            "GENERIC_AT3GPP.rx": "D0",
            "target.network-default-interface-type": "CELLULAR",
            "mbed-trace.enable": false,
            "lwip.ipv4-enabled": true,
            "lwip.ipv6-enabled": false,
            "lwip.ethernet-enabled": false,
            "lwip.ppp-enabled": true,
            "lwip.tcp-enabled": true,
            "platform.stdio-convert-newlines": true,
            "platform.stdio-baud-rate": 9600,
            "platform.default-serial-baud-rate": 9600,
            "platform.stdio-buffered-serial": true,
            "cellular.debug-at": true,
            "nsapi.default-cellular-plmn": "\"50502\"",
            "nsapi.default-cellular-sim-pin": "\"0000\"",
            "nsapi.default-cellular-apn": "\"connectme\"",
            "nsapi.default-cellular-username": 0,
            "nsapi.default-cellular-password": 0,
            "ppp.ipv4-enabled": true,
            "ppp.ipv6-enabled": false
        }

Running the Mbed-Cellular-Example Gives me this output:

[MAIN], plmn: 108768
Establishing connection
.........

Thanks!

2

Hi @zachaccino,

I may able to help here since I own this board and have successfully used the cellular-example. I am using though the EC21 not the EC25 module.

Make sure that the following is correct for your board, as suggested here. Notice in your config these are different and applicable for NUMAKER_IOT_M487.

   "NUMAKER_IOT_M263A": {
        "GENERIC_AT3GPP.provide-default": true,
        "GENERIC_AT3GPP.tx": "PE_14",
        "GENERIC_AT3GPP.rx": "PE_15"
   }

FYI, some other tips that may help during development:

  1. In your mbed_app.json enable the debugging flags for both mbed and cellurar e.g:
"mbed-trace.enable": true,
"cellular.debug-at": true

and watch for any error messages.

  1. Follow the procedure to upgrade the “NuMaker ICE firmware file” as described in the boards page at the bottom of the page if you experience any issues.

For reference here are the logs of my cellular-example running:

mbed-os-example-cellular

Built: Mar 11 2020, 10:49:30


[MAIN], plmn: 0
Establishing connection

.[2K.[39m[00000002ms][INFO][CELL]: New CellularContext  (200070d8).[0m

.[2K.[39m[00000003ms][INFO][CELL]: CellularContext plmn NULL.[0m

.[2K.[39m[00000004ms][INFO][CELL]: CellularContext connect.[0m

.[2K.[39m[00000006ms][INFO][CELL]: Start connecting (timeout 1000 ms).[0m

.[2K.[39m[00000011ms][INFO][CELL]: AT TX ( 2): AT.[0m

.[2K.[39m[00000016ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000022ms][INFO][CELL]: AT RX ( 9): AT<cr><cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000028ms][INFO][CELL]: AT TX ( 2): AT.[0m

.[2K.[39m[00000033ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000038ms][INFO][CELL]: AT RX ( 9): AT<cr><cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000045ms][INFO][CELL]: AT TX ( 4): ATE0.[0m

.[2K.[39m[00000050ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000055ms][INFO][CELL]: AT RX (11): ATE0<cr><cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000061ms][INFO][CELL]: AT TX ( 9): AT+CMEE=1.[0m

.[2K.[39m[00000067ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000072ms][INFO][CELL]: AT RX ( 6): <cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000079ms][INFO][CELL]: AT TX ( 9): AT+CFUN=1.[0m

.[2K.[39m[00000083ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000089ms][INFO][CELL]: AT RX ( 6): <cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000095ms][INFO][CELL]: Modem ready.[0m

.[2K.[39m[00000100ms][INFO][CELL]: Setup SIM (timeout 1000 ms).[0m

.[2K.[39m[00000105ms][INFO][CELL]: AT TX ( 8): AT+CPIN?.[0m

.[2K.[39m[00000111ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000116ms][INFO][CELL]: AT RX (22): <cr><ln>+CPIN: READY<cr><ln><cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000124ms][INFO][CELL]: SIM is ready.[0m

.[2K.[39m[00000129ms][INFO][CELL]: AT TX ( 8): AT+COPS?.[0m

.[2K.[39m[00000135ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000140ms][INFO][CELL]: AT RX ( 3): <cr><ln>+.[0m

.[2K.[39m[00000145ms][INFO][CELL]: AT RX (31): COPS: 0,0,"O2 - UK giffgaff",7<cr>.[0m

.[2K.[39m[00000152ms][INFO][CELL]: AT RX ( 7): <ln><cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000160ms][INFO][CELL]: AT TX ( 9): AT+CEREG=.[0m

.[2K.[39m[00000164ms][INFO][CELL]: AT TX ( 1): 2.[0m

.[2K.[39m[00000170ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000174ms][INFO][CELL]: AT RX ( 6): <cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000180ms][INFO][CELL]: AT TX ( 9): AT+CGREG=.[0m

.[2K.[39m[00000186ms][INFO][CELL]: AT TX ( 1): 2.[0m

.[2K.[39m[00000191ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000196ms][INFO][CELL]: AT RX ( 6): <cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000202ms][INFO][CELL]: AT TX ( 8): AT+CREG=.[0m

.[2K.[39m[00000208ms][INFO][CELL]: AT TX ( 1): 2.[0m

.[2K.[39m[00000213ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000217ms][INFO][CELL]: AT RX ( 6): <cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000223ms][INFO][CELL]: AT TX ( 9): AT+CGACT?.[0m

.[2K.[39m[00000229ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000235ms][INFO][CELL]: AT RX (32): <cr><ln>+CGACT: 1,1<cr><ln>+CGACT: 2,0<cr><ln>+CGA.[0m

.[2K.[39m[00000243ms][INFO][CELL]: AT RX (15): CT: 3,0<cr><ln><cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000251ms][INFO][CELL]: AT TX ( 9): AT+CGATT?.[0m

.[2K.[39m[00000255ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000261ms][INFO][CELL]: AT RX (19): <cr><ln>+CGATT: 1<cr><ln><cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000270ms][INFO][CELL]: AT TX (10): AT+CGEREP=.[0m

.[2K.[39m[00000274ms][INFO][CELL]: AT TX ( 1): 1.[0m

.[2K.[39m[00000280ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000285ms][INFO][CELL]: AT RX ( 6): <cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000290ms][INFO][CELL]: AT TX ( 6): AT+CSQ.[0m

.[2K.[39m[00000296ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000301ms][INFO][CELL]: AT RX (21): <cr><ln>+CSQ: 31,99<cr><ln><cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000309ms][INFO][CELL]: AT TX ( 6): AT+CSQ.[0m

.[2K.[39m[00000315ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000320ms][INFO][CELL]: AT RX (21): <cr><ln>+CSQ: 31,99<cr><ln><cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000329ms][INFO][CELL]: RSSI -51 dBm.[0m

.[2K.[39m[00000333ms][INFO][CELL]: AT TX ( 9): AT+CEREG?.[0m

.[2K.[39m[00000339ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000343ms][INFO][CELL]: AT RX (32): <cr><ln>+CEREG: 2,1,"01B0","7CDEC6E",7.[0m

.[2K.[39m[00000351ms][INFO][CELL]: AT RX ( 8): <cr><ln><cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000358ms][INFO][CELL]: Registering network => Attaching network.[0m

.[2K.[39m[00000365ms][INFO][CELL]: AT TX ( 6): AT+CSQ.[0m

.[2K.[39m[00000371ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000376ms][INFO][CELL]: AT RX (21): <cr><ln>+CSQ: 31,99<cr><ln><cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000384ms][INFO][CELL]: RSSI -51 dBm.[0m

.[2K.[39m[00000389ms][INFO][CELL]: Attaching network (timeout 60000 ms).[0m

.[2K.[39m[00000396ms][INFO][CELL]: AT TX ( 9): AT+CGATT?.[0m

.[2K.[39m[00000400ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000406ms][INFO][CELL]: AT RX (19): <cr><ln>+CGATT: 1<cr><ln><cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000414ms][INFO][CELL]: AT TX (11): AT+CGDCONT?.[0m

.[2K.[39m[00000420ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000425ms][INFO][CELL]: AT RX (24): <cr><ln>+CGDCONT: 1,"IPV4V6",".[0m

.[2K.[39m[00000433ms][INFO][CELL]: AT RX (32): ","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.[0m

.[2K.[39m[00000440ms][INFO][CELL]: AT RX (32): .0",0,0,0,0<cr><ln>+CGDCONT: 2,"IPV4V6.[0m

.[2K.[39m[00000447ms][INFO][CELL]: AT RX (32): ","stream.co.uk","0.0.0.0.0.0.0..[0m

.[2K.[39m[00000455ms][INFO][CELL]: AT RX (32): 0.0.0.0.0.0.0.0.0",0,0,0,0<cr><ln>+CGD.[0m

.[2K.[39m[00000462ms][INFO][CELL]: AT RX (28): CONT: 3,"IPV4V6","giffgaff.c.[0m

.[2K.[39m[00000469ms][INFO][CELL]: AT RX (32): om","0.0.0.0.0.0.0.0.0.0.0.0.0.0.[0m

.[2K.[39m[00000477ms][INFO][CELL]: AT RX (21): .0.0",0,0,0,0<cr><ln><cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00000486ms][INFO][CELL]: Found PDP context 3.[0m

.[2K.[39m[00000490ms][INFO][CELL]: CellularContext PPP connect.[0m

.[2K.[39m[00000496ms][INFO][CELL]: AT TX (16): AT+CGDATA="PPP",.[0m

.[2K.[39m[00000503ms][INFO][CELL]: AT TX ( 1): 3.[0m

.[2K.[39m[00000508ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00000522ms][INFO][CELL]: AT RX ( 9): <cr><ln>CONNECT.[0m

.[2K.[39m[00000785ms][INFO][CELL]: CellularContext IP 10.147.58.142.[0m


Connection Established.
IP Address is 10.147.58.142
TCP: connected with echo.mbedcloudtesting.com server
TCP: Sent 4 Bytes to echo.mbedcloudtesting.com
Received from echo server 4 Bytes

.[2K.[39m[00002074ms][INFO][CELL]: CellularContext disconnect().[0m

.[2K.[39m[00002081ms][INFO][CELL]: AT TX ( 8): AT+CMEE?.[0m

.[2K.[39m[00002082ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00002086ms][INFO][CELL]: AT RX ( 5): <cr><ln>NO .[0m

.[2K.[39m[00002087ms][INFO][CELL]: AT RX ( 9): CARRIER<cr><ln>.[0m

.[2K.[33m[00003082ms][WARN][CELL]: AT timeout.[0m

.[2K.[33m[00003082ms][WARN][CELL]: AT timeout.[0m

.[2K.[39m[00003083ms][INFO][CELL]: AT TX ( 8): AT+CMEE?.[0m

.[2K.[39m[00003084ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00003087ms][INFO][CELL]: AT RX ( 3): <cr><ln>+.[0m

.[2K.[39m[00003088ms][INFO][CELL]: AT RX (15): CMEE: 1<cr><ln><cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00003092ms][INFO][CELL]: cellular_callback: PPP mode and NSAPI_STATUS_DISCONNECTED.[0m

.[2K.[39m[00003101ms][INFO][CELL]: AT TX ( 8): AT+CMEE?.[0m

.[2K.[39m[00003107ms][INFO][CELL]: AT TX ( 1): <cr>.[0m

.[2K.[39m[00003111ms][INFO][CELL]: AT RX (18): <cr><ln>+CMEE: 1<cr><ln><cr><ln>OK<cr><ln>.[0m

.[2K.[39m[00003120ms][INFO][CELL]: CellularContext disconnected.[0m


Success. Exiting

Hope that helps,

-Christos

1 Like
3

Thank you for your reply!
I finally got it working properly!

Turns out… You need to use the DC power to allow the EC25 to be able to work properly! (Which should be blatantly obvious…)

To work with mbed-cellular-example, you need to do the following steps:

Step 1

Follow the README carefully.

Step 2

The cellular configurations can be like this:

"nsapi.default-cellular-plmn": 0,
"nsapi.default-cellular-sim-pin": "\"0000\"",
"nsapi.default-cellular-apn": 0,
"nsapi.default-cellular-username": 0,
"nsapi.default-cellular-password": 0,

A note here is that you have to set your SIM PIN to “0000” on your mobile phone explicitly. (Tho, disable sim pin and provide 0 in the nsapi.default-cellular-sim-pin should also work? I haven’t tried it.). Setting PLMN, APN, USERNAME, and PASSWORD to 0 means it is either not set or automatically configured once it is connected.

Or, you can explicitly set the parameters like this (Assuming you are using YesOptus APN):

"nsapi.default-cellular-plmn": "\"50502\"",
"nsapi.default-cellular-sim-pin": "\"0000\"",
"nsapi.default-cellular-apn": "\"connectme\"",
"nsapi.default-cellular-username": 0,
"nsapi.default-cellular-password": 0,

Step 3

Make sure you have DC Power in addition to the USB Power. (Otherwise, the EC25 doesn’t have enough power to work properly.)

Step 4

Update your firmware if you can. For NuMaker, @cvasilak already mentioned it.

Step 5

Make sure your serial monitor’s baud rate is 115200 or as specified in the mbed_app.json

Finally

You can compile and upload it to your board and see if it works.

Hope this helps.

4

glad that you make it work!

…and thanks for taking the time to write the steps to helps others, appreciated! :+1:

5

Hello,
Looking at this post and asking questions, I look for resources to use EC21 as cellular…

I set up and manipulated the same as in the example.
But after CONNECT’s RX log, the answer works differently from the example.

The only difference is that after a CellularContext PPP connection, AT + CGDATA = “PPP” is not sent, and ATD * 99 *** is sent.

So I’m getting stack overflow in Iwip_tcpip and an MbedOS error.

What is the reason…?

I will attach the log below…

Establishing connection
[00000004ms][INFO][CELL]: New CellularContext (0x20006b08)
[00000005ms][INFO][CELL]: CellularContext plmn NULL
[00000007ms][INFO][CELL]: CellularContext connect
[00000010ms][INFO][CELL]: AT TX ( 6): AT+CSQ
[00000011ms][INFO][CELL]: AT TX ( 1):
[00000016ms][INFO][CELL]: AT RX (16): +CSQ: 31,99
[00000024ms][INFO][CELL]: AT RX ( 5): OK
[00000030ms][INFO][CELL]: RSSI -51 dBm
[00000034ms][INFO][CELL]: Start connecting (timeout 5000 ms)
[00000041ms][INFO][CELL]: AT TX ( 2): AT
[00000046ms][INFO][CELL]: AT TX ( 1):
[00000051ms][INFO][CELL]: AT RX ( 6): OK
[00000057ms][INFO][CELL]: AT TX ( 2): AT
[00000062ms][INFO][CELL]: AT TX ( 1):
[00000067ms][INFO][CELL]: AT RX ( 6): OK
[00000074ms][INFO][CELL]: AT TX ( 6): AT+CSQ
[00000079ms][INFO][CELL]: AT TX ( 1):
[00000084ms][INFO][CELL]: AT RX (16): +CSQ: 31,99
[00000091ms][INFO][CELL]: AT RX ( 5): OK
[00000097ms][INFO][CELL]: RSSI -51 dBm
[00000102ms][INFO][CELL]: AT TX ( 4): ATE0
[00000107ms][INFO][CELL]: AT TX ( 1):
[00000112ms][INFO][CELL]: AT RX ( 6): OK
[00000118ms][INFO][CELL]: AT TX ( 9): AT+CMEE=1
[00000123ms][INFO][CELL]: AT TX ( 1):
[00000128ms][INFO][CELL]: AT RX ( 6): OK
[00000135ms][INFO][CELL]: AT TX ( 9): AT+CFUN=1
[00000140ms][INFO][CELL]: AT TX ( 1):
[00000145ms][INFO][CELL]: AT RX ( 6): OK
[00000151ms][INFO][CELL]: Modem ready
[00000157ms][INFO][CELL]: AT TX ( 6): AT+CSQ
[00000161ms][INFO][CELL]: AT TX ( 1):
[00000166ms][INFO][CELL]: AT RX (16): +CSQ: 31,99
[00000174ms][INFO][CELL]: AT RX ( 5): OK
[00000180ms][INFO][CELL]: RSSI -51 dBm
[00000184ms][INFO][CELL]: Setup SIM (timeout 5000 ms)
[00000190ms][INFO][CELL]: AT TX ( 8): AT+CPIN?
[00000196ms][INFO][CELL]: AT TX ( 1):
[00000201ms][INFO][CELL]: AT RX (16): +CPIN: READY
[00000208ms][INFO][CELL]: AT RX ( 6): OK
[00000214ms][INFO][CELL]: SIM is ready
[00000219ms][INFO][CELL]: AT TX ( 8): AT+COPS?
[00000224ms][INFO][CELL]: AT TX ( 1):
[00000230ms][INFO][CELL]: AT RX (16): +COPS: 0,0,“SK
[00000236ms][INFO][CELL]: AT RX (16): Telecom”,7OK
[00000243ms][INFO][CELL]: AT RX ( 2):
[00000248ms][INFO][CELL]: AT TX ( 8): AT+CEREG
[00000254ms][INFO][CELL]: AT TX ( 1): =
[00000258ms][INFO][CELL]: AT TX ( 1): 2
[00000263ms][INFO][CELL]: AT TX ( 1):
[00000268ms][INFO][CELL]: AT RX ( 6): OK
[00000275ms][INFO][CELL]: AT TX ( 8): AT+CGREG
[00000280ms][INFO][CELL]: AT TX ( 1): =
[00000285ms][INFO][CELL]: AT TX ( 1): 2
[00000289ms][INFO][CELL]: AT TX ( 1):
[00000294ms][INFO][CELL]: AT RX ( 6): OK
[00000301ms][INFO][CELL]: AT TX ( 7): AT+CREG
[00000306ms][INFO][CELL]: AT TX ( 1): =
[00000311ms][INFO][CELL]: AT TX ( 1): 2
[00000316ms][INFO][CELL]: AT TX ( 1):
[00000321ms][INFO][CELL]: AT RX ( 6): OK
[00000327ms][INFO][CELL]: AT TX ( 9): AT+CGACT?
[00000332ms][INFO][CELL]: AT TX ( 1):
[00000338ms][INFO][CELL]: AT RX (16): +CGACT: 1,1+
[00000345ms][INFO][CELL]: AT RX (15): CGACT: 16,0+C
[00000351ms][INFO][CELL]: AT RX (14): GACT: 17,0+C
[00000358ms][INFO][CELL]: AT RX (14): GACT: 2,1+CG
[00000364ms][INFO][CELL]: AT RX (13): ACT: 3,0+CG
[00000371ms][INFO][CELL]: AT RX (13): ACT: 4,0O
[00000377ms][INFO][CELL]: AT RX ( 3): K
[00000383ms][INFO][CELL]: AT TX ( 9): AT+CGATT?
[00000388ms][INFO][CELL]: AT TX ( 1):
[00000393ms][INFO][CELL]: AT RX (16): +CGATT: 1O
[00000401ms][INFO][CELL]: AT RX ( 3): K
[00000407ms][INFO][CELL]: AT TX (10): AT+CGEREP=
[00000412ms][INFO][CELL]: AT TX ( 1): 1
[00000417ms][INFO][CELL]: AT TX ( 1):
[00000422ms][INFO][CELL]: AT RX ( 6): OK
[00000429ms][INFO][CELL]: AT TX ( 6): AT+CSQ
[00000433ms][INFO][CELL]: AT TX ( 1):
[00000438ms][INFO][CELL]: AT RX (16): +CSQ: 31,99
[00000445ms][INFO][CELL]: AT RX ( 5): OK
[00000452ms][INFO][CELL]: AT TX ( 6): AT+CSQ
[00000457ms][INFO][CELL]: AT TX ( 1):
[00000462ms][INFO][CELL]: AT RX (16): +CSQ: 31,99
[00000469ms][INFO][CELL]: AT RX ( 5): OK
[00000475ms][INFO][CELL]: RSSI -51 dBm
[00000480ms][INFO][CELL]: AT TX ( 8): AT+CEREG
[00000485ms][INFO][CELL]: AT TX ( 1): ?
[00000490ms][INFO][CELL]: AT TX ( 1):
[00000495ms][INFO][CELL]: AT RX (16): +CEREG: 2,1,“3
[00000501ms][INFO][CELL]: AT RX (16): 705”,“21EA347”,7
[00000508ms][INFO][CELL]: AT RX ( 8): OK
[00000514ms][INFO][CELL]: Registering network => Attaching network
[00000522ms][INFO][CELL]: AT TX ( 6): AT+CSQ
[00000527ms][INFO][CELL]: AT TX ( 1):
[00000532ms][INFO][CELL]: AT RX (16): +CSQ: 31,99
[00000539ms][INFO][CELL]: AT RX ( 5): OK
[00000545ms][INFO][CELL]: RSSI -51 dBm
[00000550ms][INFO][CELL]: Attaching network (timeout 5000 ms)
[00000557ms][INFO][CELL]: AT TX ( 9): AT+CGATT?
[00000562ms][INFO][CELL]: AT TX ( 1):
[00000567ms][INFO][CELL]: AT RX (16): +CGATT: 1O
[00000575ms][INFO][CELL]: AT RX ( 3): K
[00000581ms][INFO][CELL]: AT TX (11): AT+CGDCONT?
[00000586ms][INFO][CELL]: AT TX ( 1):
[00000592ms][INFO][CELL]: AT RX (16): +CGDCONT: 1,“I
[00000598ms][INFO][CELL]: AT RX (16): PV4V6”,“lte-inte
[00000604ms][INFO][CELL]: AT RX (16): rnet.sktelecom.c
[00000610ms][INFO][CELL]: AT RX (16): om”,“0.0.0.0.0.0
[00000617ms][INFO][CELL]: AT RX (16): .0.0.0.0.0.0.0.0
[00000623ms][INFO][CELL]: AT RX (16): .0.0”,0,0,0,0+
[00000629ms][INFO][CELL]: AT RX (15): CGDCONT: 16,“IP
[00000634ms][INFO][CELL]: AT RX (16): V4V6”,“lte-inter
[00000640ms][INFO][CELL]: AT RX (16): net.sktelecom.co
[00000647ms][INFO][CELL]: AT RX (16): m”,“0.0.0.0.0.0.
[00000653ms][INFO][CELL]: AT RX (16): 0.0.0.0.0.0.0.0.
[00000659ms][INFO][CELL]: AT RX (16): 0.0”,0,0,0,0+C
[00000665ms][INFO][CELL]: AT RX (14): GDCONT: 17,“IP
[00000671ms][INFO][CELL]: AT RX (16): “,“internet”,“0.
[00000677ms][INFO][CELL]: AT RX (16): 0.0.0”,0,0,0,0
[00000684ms][INFO][CELL]: AT RX (16): +CGDCONT: 2,“IPV
[00000690ms][INFO][CELL]: AT RX (16): 4V6”,“IMS”,“0.0.
[00000696ms][INFO][CELL]: AT RX (16): 0.0.0.0.0.0.0.0.
[00000702ms][INFO][CELL]: AT RX (16): 0.0.0.0.0.0”,0,0
[00000708ms][INFO][CELL]: AT RX (16): ,0,0+CGDCONT:
[00000715ms][INFO][CELL]: AT RX (16): 3,“IPV4V6”,””,"0
[00000721ms][INFO][CELL]: AT RX (16): .0.,0+CGDCONT:
[00000728ms][INFO][CELL]: AT RX (13): 4,1OK
[00000735ms][INFO][CELL]: Found PDP context 16
[00000740ms][INFO][CELL]: CellularContext PPP connect
[00000746ms][INFO][CELL]: AT TX ( 9): ATD99**
[00000752ms][INFO][CELL]: AT TX ( 2): 16
[00000757ms][INFO][CELL]: AT TX ( 1): #
[00000761ms][INFO][CELL]: AT TX ( 1):
[00000766ms][INFO][CELL]: HERE1
[00000772ms][INFO][CELL]: AT RX ( 6): CONN
[00000776ms][INFO][CELL]: AT RX (12): ECT 384000

++ MbedOS Error Info ++
Error Status: 0x80020125 Code: 293 Module: 2
Error Message: CMSIS-RTOS error: Stack overflow
Location: 0x8019A49
Error Value: 0x1
Current Thread: lwip_tcpip Id: 0x200014A0 Entry: 0x800B795 StackSize: 0x4B0 StackMem: 0x200076B8 SP: 0x20013F24
For more info, visit: mbedos-error
– MbedOS Error Info –

Please help me if you look at this article… I’ve been having a very hard time for about a month because the EC21 module is not working.