Unable to detect SIM on custom PCB and SIM VCC never goes high

[Deval]

I am using the SLM project with pppd and cmux for Linux on my custom board. I am able to create CMUX and communicate with the nrf 9151 using the CMUX AT port using my custom overlay (which only changes the UART pins). But I am unable to create the pppd because the SIM Card is not detected. 

When I probe the SIM VCC line I always see 0 V. On the nrf9151 DK with the same project I can see that same pin go high and the example project works. 

This is the output I see with the AT commands. 

AT+CFUN=1

OK
AT%XSIM?

%XSIM: 0,9

OK
AT+CEREG?

+CEREG: 0,90

More information. 

AT%SHORTSWVER

%SHORTSWVER: nrf91x1_2.0.2

Do I need to do any additional configuration for the SIM pins? What should I be seeing on all the SIM pins?

[MJJ]

Hi Jennifer, Greg, 

 

Great ideas and thanks for getting to the root cause of this! That was it -- the primary issue on our end is that the SIM card holder we used in this run of boards didn't have an internal switch that connects C5 to GND when the SIM is installed, so C5 and therefore our SIM was never getting properly grounded. 

After grounding C5, we're able to correctly communicate with the SIM and see activity on the IO line with responses for all of the commands I was previously issuing. We're in the same place now with our boards as the DK. 

 

Thank you all for your help debugging this issue! We'll move forward from here and will reach out if there's anything else we run into along the way.

-Andreea