Blinky firmware does'nt start without jlink connection on NRF52833 custom board

[fgaultier]

Hi,

We built the Blinky sample with NRF Connect SDK 1.3.1. It works fine on NRF52833 DK, but when flashing on external custom NRF52833 board the firmware won't start without j-link connection established.

Anyone has a clue about what's going on ?

Best regards,

[koniho]

This can happen if the firmware is built with Blocking mode RTT, i.e. `#define SEGGER_RTT_CONFIG_DEFAULT_MODE 2 // blocking`

[fgaultier]

It does'not seem to be the case and the same firmware runs fine on NRF52833 DK

[Edvin]

Hello,

Do you have an LFXTAL on your custom nRF52833 board? If not, did you set the correct LFCLK settings in your application? 

When something works on a Nordic DK but not a custom board, that is usually the reason. The LFXTAL is not present, and hence the BLE stack doesn't work properly.

So do you have an external LFXTAL (32kHz) on your custom board?

BR,

Edvin

[fgaultier]

Yes we have an LFXTAL on our custom board and it should be working fine. Our firmware example does not involve any BLE. Is LFXTAL used even in those cases ?

How do you set the LFCLK settings in the application ? We use NCS and Zephyr Blinky sample.

[Edvin]

Hello,

I have an nRF52832 DK with a broken LFXTAL, and I tested the ncs\zephyr\samples\basic. I noticed that when I flash this sample on this DK, it automatically selects the RC oscillator, while if I flash it to a DK with a working LFXTAL, it selects the XTAL, so I suspect that Zephyr tries with the XTAL first, and then moves over to the RC oscillator if the XTAL is not responding. So I don't think that is actually the issue.

I tested the nRF52833 DK without the debugger attached as well, but obviously, as you already described, that works as well.

Do you have any way of monitoring the logs when the debugger is not connected. Either a standalone UART device (TTL-232) or another nRF DK that you can connect the UART pins on and monitor the UART log? In that case, does the log say anything when the debugger is not attached?

The log should say:

*** Booting Zephyr OS build v2.3.0-rc1-ncs1  ***

If it doesn't say anything more, try to add the line:

CONFIG_ASSERT=y

to your prj.conf file and check the log again.

Best regards,

Edvin