NRF 5340 programmed but will not run

[Mike Amend]

• Successfully programmed via SWO (Debug connector to programmer/VSCode)
• Successfully programmed via NRF Connect Programmer using J-Link SWO
• Checked power rails to be 1.8v
• Checked Reset is at 1.8v after power up
• Issue has occurred on 2 boards
• Used known good code working on other boards
• These 2 boards worked until the issue occurred
• Now on power-up, there is no sign of life/code execution
• Nothing coming out RTT after power up
• What might cause the NRF 5340 to appear bricked?

[Kazi Afroza Sultana]

Hello,

I think the first thing you can try is to recover the device by nrfjprog --recover which will 

1. Perform an ERASEALL via the CTRL-AP
2. Program the required firmware before a reset is executed; source:  Allowing debugger access to nRF5340 - Blogs - Nordic Blog - Nordic DevZone

Because nRf5340 requires firmware to explicitly enable debugger access on every boot.

When we do nrfjprog --recover, it works for both. If it does not work you can try separate reset and erasell by nrfjprog.

Besides this I would like to know if you have external low frequency crystal on your custom board. If not, you have to set internal RC in the prj.conf file of the application

CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y
CONFIG_CLOCK_CONTROL_NRF_K32SRC_500PPM=y
CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC_CALIBRATION=y
CONFIG_CLOCK_CONTROL_NRF_CALIBRATION_LF_ALWAYS_ON=y

You can try these and let me know if these help.

Thanks.

BR

Kazi