nRF9160DK high fluctuation and inconsistent boot time

[raymond.zhang]

Hi,

I am using nRF9160DK, nrf v0.4.0, zephyr v1.14.99-ncs1

I have been trying to measure the boot time from when I press the reset to when it gets to the start of the application code. I am getting very consistent timing from the kernel to the application and very consistent timing from the spm jump to the kernel and from the start of the spm main to the spm jump. I am using a logic analyzer and toggling GPIO pins at those specific points in the code to mark the time. What goes wrong is from the start of the reset to the spm main is very inconsistent, varying between 200us to 1.2ms with no noticeable pattern at all. The assumption is that there is probably something in between the reset and the nRF9160 that is introducing this variable. Is there a reliable test point where I can measure the reset line to the nRF9160 with the least amount of interference in between? Or could this be due to other reasons?

Thank you,

Raymond

[Martin Lesund]

Hi Raymond, 
To get a more viable test result I would highly recommend doing the tests with the newest firmware, both the modem firmware and application version since this can have an effect on the result.

Please follow the directions in this blog on how to upgrade.

[raymond.zhang]

Hi Martin,

I will try to do a test on that. One thing I would like to clarify is the secure boot portion of the code. Can you or anyone confirm where is the start and end of the execution of the secure boot code? That is essentially what i want to measure.

Thanks,

Raymond