Can connect to cellular with evaluation board but not with custom board (with the same sim)

[Byter]

Hello, I've been trying to connect to cellular from our custom board (using nrf9160_ns) for the past few days. It already worked with the evaluation board using the same sim from Pelephone. Later I used the at_client sample (from sdk version 2.6.1) in order to use AT commands to check things more in depth and here's what I found:

I started with the custom board. After activating the sim it starts with the following values:

AT+CFUN=1
OK
> AT+CPIN?
+CPIN: READY
OK
> AT+CESQ
+CESQ: 99,99,255,255,255,255
OK
> AT+XCBAND
ERROR
> AT%XCBAND
%XCBAND: 28
OK
> AT%XBANDLOCK?
%XBANDLOCK: "",""
OK
> AT+COPS?
+COPS: 0
OK
AT+CGDCONT?
+CGDCONT: 0,"","","",0,0
OK

And after a while it changes to:

> AT+CEREG?
+CEREG: 0,2,"1D75","001A040B",7
OK
> AT+CESQ
+CESQ: 99,99,255,255,6,10
OK
> AT%XCBAND
%XCBAND: 0
OK
---- After more time ----
> AT%XCBAND
%XCBAND: 3
OK
> AT+COPS?
+COPS: 0
OK

The device has the following version:
> AT+CGMR
mfw_nrf9160_1.3.6
OK

Also I called AT+CEREG? every one in a while and it's either trying to connect (like the output above) or in the 0, 2 state

Now to compare it with the evaluation board:

> AT+CFUN=1
OK
> AT+CGDCONT?
+CGDCONT: 0,"IPV4V6","sphone.pelephone.net.il","10.92.102.85 2A02:6680:210B:DEE0:D957:27EA:952F:1B4C",0,0
OK
> AT+CPIN?
+CPIN: READY
OK
> AT+CESQ
+CESQ: 99,99,255,255,11,37
OK
> AT%XCBAND
%XCBAND: 28
OK
> AT%XBANDLOCK?
%XBANDLOCK: "",""
OK
> AT+COPS?
+COPS: 0,2,"42503",7
OK

As you can see it almost immediately connected and it already has the context (AT+CGDCONT). Now, I've tried to manually set the context for the custom board as well but it just hangs (I tried both with 0 and 1 as the first value).

In addition, here's the output from an app we're developing that originated from the mqtt sample:

From the custom board:
*** Booting nRF Connect SDK v3.5.99-ncs1 ***
[00:00:00.383,697] <inf> network: Bringing network interface up and connecting to the network
+CEREG: 2,"1D75","001A040B",7
+CEREG: 2
+CEREG: 2,"7E9B","00A6402A",9

// And it goes back and forth between something and 2 for a long time

As opposed to the evaluation board:
*** Booting nRF Connect SDK v3.5.99-ncs1 ***
[00:00:00.375,488] <inf> network: Bringing network interface up and connecting to the network
+CEREG: 2,"1D75","001A040B",7
+CSCON: 1
+CGEV: ME PDN ACT 0
+CEREG: 1,"1D75","001A040B",7,,,"11100000","11100000"
[00:00:05.018,066] <inf> network: Network connectivity established
+CGEV: IPV6 0

// And it happened almost instantly

(I removed unrelated logs between the network logs)

So I've come to a halt and don't know what else to try. Any help would be appreciated and let me know if you need more information.

EDIT:
Here are the tracing results:

It starts at 8 because I AT+CFUN=1 before I set the AT+CGDCONT so I set it to 0 and then to 1 again so that's where the actual tracing starts. Here is the AT commands log (I've tried 2 contexts and the second one worked while the first one didn't as you can soon see):

> AT+CFUN=1
OK
> AT+CEREG?
+CEREG: 0,4
OK
> AT+CGDCONT?
OK
> AT+CEREG?
+CEREG: 0,4
OK
> AT+CFUN=0
OK
> AT+CGDCONT=1,"IPV4V6","sphone.pelephone.net.il"
OK
> AT+CFUN=1
OK
> AT+CEREG?
+CEREG: 0,4
OK
> AT+CEREG=1
OK
> AT+CEREG?
+CEREG: 1,4
OK
> AT+CEREG?
+CEREG: 1,4
OK
> AT+CFUN=0
+CEREG: 0
OK
> AT+CGDCONT=0,"IPV4V6","sphone.pelephone.net.il"
OK
> AT+CFUN=1
OK
> AT+CEREG?
+CEREG: 0,4
OK
> AT+CEREG?
+CEREG: 0,4
OK
> AT+CEREG?
+CEREG: 0,4
OK
> AT+CEREG?
+CEREG: 0,4
OK
> AT+CEREG?
+CEREG: 0,4
OK
> AT+CEREG?
+CEREG: 0,4
OK
> AT+CEREG?
+CEREG: 0,2,"1D75","001A0401",7
OK
+CEREG: 0,2
OK
> AT+CEREG?
> AT+CEREG?
+CEREG: 0,2
OK
> AT+CEREG?
+CEREG: 0,2
OK
> AT+CEREG?
+CEREG: 0,2,"0367","00335621",7
OK

That's in comparison with the modem trace on the evaluation board:

where I simply wrote AT+CFUN=1 and this whole operation occured

[Charlie]

Hi Avishay,

This is Charlie, and I am looking at this ticket due to Øyvind  is not available.

The previous CESQ responses with rsrp value 10 and 37, which corresponding to -130dBm and -103dBm signal strength. These two values reflect poor signal strength. Which make the device stay at the following connection states.

2 – Not registered, but UE is currently trying to attach or searching an operator to register to

4 – Unknown (for example, out of Evolved Terrestrial Radio Access Network (E-UTRAN) coverage)

Can you confirm if you or your colleague have request hardware review or antenna tuning? I do not see you have other hardware related ticket. 

If you have reserved external antenna connector on your custom board, you can also try to test with external antenna to see if it will make any difference.

Best regards,

Charlie

[Byter]

Hi Charlie,

After further investigation, we looked again for the impedance on the PCB design Gerber files.

We've been doing the impedance until the first element on the antenna matching circuit. Under the antenna matching elements until the antenna component we didn't do any impedance layer.

Is this the correct design?

Additionally, we can send you the Gerber or drd files.

[Charlie]

Hi Avishay,

Do you mean you have requested antenna tuning for your current PCB board?

Did you get any advice about the match network components value, or it is just OK without needs for adjustment?

You could do side by side comparison with an nRF9160DK to further confirm the suspicion about the weak signal.

Best regards,

Charlie

[Byter]

Hi Charlie,

Our board was checked by the antenna manufacturer.

They provided component location instructions, component routing instructions and impedance.

It's possible that the manufacturer's recommendations were incorrect.

[Charlie]

Hi Avishay,

Feel free to generate a new private ticket and request free antenna tuning service from us.

Best regards,

Charlie

[Byter]

Hi Charlie,

Thank you. What files do you need us to provide?

On another note, we tried the XRFTEST commands and are curious what do these results mean:

AT+CMEE=1
OK
> AT%XRFTEST=0,1,3,8000,-75,0
+CME ERROR: 0
> AT%XRFTEST=1,1,5,8300,18,0,3,12,0
%XRFTEST: 0
OK

We copied the exact values from the examples of pages 14 and 15 in the nrf9160 hardware integration guide

[Charlie]

Antenna tuning is different with RF circuit design. You can learn about antenna tuning here https://youtu.be/x1m8G8MAeUQ?si=fSr_QNilFlcWliKv.

When you generate a new private ticket to request antenna tuning. My colleague working on HW will request some HW samples of your product and check your antenna design and RF components, then give you advice. 

For the test command, you can refer to Production test commands (nordicsemi.com) to decode the test commands.

Best regards,

Charlie