troubleshooting of produced prototype: nrf9160

[David]

Hello,

I have developed 10pcs of one prototype with the nrf9160 SiP. 

I have some questions regarding some errors im having.

Regarding the SIM 1V8 driver VCC, for UICC interface, I am observing a fluctuation on this channel/voltage, from 0V -> 0.4 VDC, with approximately 1hz frequency.

What can cause this to happend, what is the normal behaviour of this channel when it is short-circuited with ground or something else/similar ?

My second question is regarding the attached image, im observing this on a few of my prototypes, im not able to upload any modem firmware to the SiP, any idea why?

Regards,

David

[Didrik Rokhaug]

Could you give me some more information about how your application fails?

Are you not able to program it, or does it fail at run-time?

What error messages do you get?

 

David said:

I've read up on the SPM, and for everything to work, I have to first upload the SPM firmware without "ns", then I have to upload my application firmware, as "ns".

Also, I have to set in proj.conf, CONFIG_SPM=n for this to be available as .elf, for me to build. If not, this wont work.

 While it is true that you had to flash the two applications separately before, that is no longer necessary. If you build for the non-secure version of a board (with "ns" at the end of the board name), it should configure the application correctly, build the Secure Partition Manager and merge the hex files into a single merged.hex.

What happens if you remove the CONFIG_SPM and CONFIG_TRUSTED_NONSECURE lines from your prj.conf, and add

include($ENV{ZEPHYR_BASE}/../nrf/cmake/boilerplate.cmake)

right above the other include macro in your CMakeLists.txt file?

[David]

Hello,

I've managed to get the prototype working with my application, when following this tutorial 

https://devzone.nordicsemi.com/nordic/cellular-iot-guides/b/getting-started-cellular/posts/nrf-connect-sdk-tutorial.

Therefore, I now have to solve the sim-interface issue on my prototype.

I only had 10uF ceramics laying around, so I added 4 for IO_supplyu/DEC0.

If I cut the 1V8 sim vdd trace, which goes to the analoge switch, I still can measure the same fluctuation on this voltage, when measuring between "gnd / analoge switch pin 14".

I can even measure it on the analoge switch VCC input "pin 14", even if it is not connedted to the 1V8 sim vdd from nrf9160 SiP.

I have checked the close-by traces for this analoge switch, and these are (SIM_IO, SIM_CLK, SIM_RST).

See attached pictures below, for visual.

What can be causing this ?, I think it can have something to do with the SIM_IO, SIM_CLK, SIM_RST lines?

At what circumstances does the sim-interface behave this way?

Regards, David

[Andreas]

Hi David,

 

It might seem like this is in some way related to your HW, either the PCB design or SiP internal. Have you been able to get it working if shorting the SIM traces past U8?

Just to be on the safe side, I am assuming your prototype is behaving normally otherwise? What voltage are you seeing on DEC0 (should be 2.2V)?

 

I will be forwarding internally to get someone who knows the SIM module to comment.

 

Best regards,

Andreas

[Andreas]

Hi,

 

Another thing, looking at the pictures, you have cut SIM_1V8 between J7/U8 and nRF9160, but from the second picture you are measuring SIM_1V8 at pin 2 of J7. Fair enough. But looking at the layout I am not seeing how this pad/net is connected to the SIM_1V8 from the SiP, that is only fed into the VCC pin:

Is there any external strap, internal layers or anything that I am missing?

 

Best regards,

Andreas

[David]

Hello,

If I meassure the voltage on some other boards of my prototype, I meassure a stable 2.2V on DEC0, on the one prototype that I am having the issue with the sim-interface voltage, I meassure here between 2.1 and 2.2 VDC, oscillation. 

As I mentioned here first, I have 3 other boards of the same prototype, which does not have the fluctuation on the SIM 1V8 VDD, but on these I meassure 0VDC on SIM-interface VDD.

I am still waiting for the correct capacitor components, for DEC0 -> GND. Therefore, DEC0 is floating at the moment.

I have not tested "shorting the SIM traces past U8", do you mean SIM_IO, SIM_CLK, SIM_RST ?, should I test shorting all these together?

Regards, David