nrf5340 Bluetooth only works when JLink is connected

[AkuAku]

Hello,

I ordered a nRF5340-PDK board and i'm trying to get it to work.

When flashing the Heart Rate hex file I couldn't find the device (i pushed the reset button).

I tried building from source and it works only with JLink connected (in SES).

I added code to blink an LED to the Heart Rate sampled and flashed it. The LED blinks even without JLink being connected.

So I'm guessing somehow this is related to the network processor? Reading the flash in the programmer utility shows the network processor is flashed properly.

What could be the cause of this issue?

Thanks in advance.

[Andreas L]

I am also seeing a similar issue on a custom battery powered nRF5340 PCB using latest NCS. After power on BLE does not come up. Attaching a segger and doing a reset in Ozone will always clear the issue and BLE will work until the next time power is removed and reattached.

I tried doing a software timeout if BT initialization failed, and then a watchdog reset. The device then starts advertising, but it need a lot of retries on GATT write/reads (using a python bluepy script). After a debugger reset I don't see the retries.

Pinreset also seems to fix the issue, but I don't know if this is possible to trigger from software ?

[haakonsh]

What version of NCS are you guys on, the v1.2.0 tag or a master branch commit? 

[Andreas L]

I've seen the issue since starting using ncs some time in january; using master commits and also the v.1.2.0 tag. I don't believe this is something that has been introduced lately in code. Still haven't looked at the network core log, but I will try to setup output and track that today