Cannot get modem out of sleep mode/no power to UICC

RE: Cannot get modem out of sleep mode/no power to UICC

luc_eac — Fri, 15 Apr 2022 14:15:06 GMT

The issue has been fixed. It turned out to be a faulty connection to the sim card slot. Two pins were assumed to be not connected internally and were connected to GND, but one of these pins is internally connected to the IO pin, pulling that to GND.

RE: Cannot get modem out of sleep mode/no power to UICC

Håkon Alseth — Tue, 05 Apr 2022 08:13:54 GMT

Thanks for sharing the SIM connections.

This seems to be the SIM card holder that you're using:

https://www.molex.com/pdm_docs/sd/1042240820_sd.pdf

Could you try and trace (measure with a multimeter) the VCC/CLK/RST/IO from the holder itself to the nRF9160 and see if there's any mismatch?

Kind regards,

Håkon

RE: Cannot get modem out of sleep mode/no power to UICC

luc_eac — Mon, 04 Apr 2022 13:48:16 GMT

This is the schematic of our connection between the nrf9160 and the sim card.

RE: Cannot get modem out of sleep mode/no power to UICC

Håkon Alseth — Mon, 04 Apr 2022 13:24:11 GMT

Hi,

As per the documentation of the CEREG output:

https://infocenter.nordicsemi.com/topic/ref_at_commands/REF/at_commands/nw_service/cereg_read.html?cp=2_1_7_6_1

This line indicates that the nRF has problems communicating with your SIM:

D: +CEREG notification: +CEREG: 90

Can you please attach your schematic/layout so we can have a look at how you've wired up the SIM?

Kind regards,

Håkon

RE: Cannot get modem out of sleep mode/no power to UICC

luc_eac — Mon, 04 Apr 2022 08:39:23 GMT

Thank you for your suggestion, it makes sense to me that that would be the problem. I did some investigation, but have not quite yet reached the root cause of the issue.

I have double-checked all pinouts on our schematic, for the SIM connector, protection IC and the NRF9160. I could not find any errors there. I have also verified that the protection IC is 1V8 compatible. The SIM cards are known to work, as they perform well in the Thingy91.

I connected another board to verify that there was not some fault specific to the first board, but the behaviour remained exactly the same.

I did some more measurements on the SIM connector:

The power line behaves as before. The data line shows no action. Both the clock and reset lines switch identically and similar to the power line, only switching on a fraction later. What seems weird to me is that the clock signal only reaches about half the VCC voltage.

More suggestions on what the problem might be are welcome!

Edit: I noticed that I had my compatibilities wrong. Our system uses SiP revision 1 while I picked the most recent modem firmware (1.3.1) and the most recent SDK version (1.9.0 at the time), which are not compatible according to the documentation.j I have downgraded to modem firmware 1.2.7 and SDK version 1.5.1, but the behaviour remains the same.

RE: Cannot get modem out of sleep mode/no power to UICC

ketiljo — Wed, 30 Mar 2022 13:05:21 GMT

Seems the modem can't find the SIM card properly. Are you sure the pinout and connection is correct in your board?