NRF52 doesn't start without debugger (Jlink) on GCC toolchain

RE: NRF52 doesn't start without debugger (Jlink) on GCC toolchain

Bjørn Kvaale — Tue, 28 Nov 2017 12:55:48 GMT

Hi Thomas, good to hear that you figured it out! I will mention it to my boss and hopefully this will be changed in the future. You might want to take a look at this case, as it is somewhat similar.

RE: NRF52 doesn't start without debugger (Jlink) on GCC toolchain

Thomas — Mon, 27 Nov 2017 02:18:29 GMT

There were several issues, intertwined. One of them raises interesting questions.

Easy stuff, we left the RTT setup in the sdk_config.h to blocking, so yea it was blocking of course. LOG frontend was waiting forever that a backend picks the logs. duh...
Something Nordic might want to look into: For people with multiple hardware like us, some of our systems will have a low frequency crystal and some others won't. In the current setup (SDK14), it is impossible to use the board files to define that (clock source and softdevice clock source). That creates very subtle bugs:

imagine you are using a clock source for LF crystal on a configuration that doesn't have such crystal. It will look like it is working. If you then use a bootloader and DFU it will stop working with no apparent reason. Inside the bootloader is a routine to disable and re-enable the clock source that will fail in an infinite loop waiting for the crystal system to stop running.

It took us multiple days to find this out. We saw 2 reasons for that:

As far as we know there is no way to tell that a board has or not a hardware LF crystal in the board file for SDK14+ (and prior I believe)
Since the bug appears far removed from its origin, it is very hard to find and reproduce. Having a #define or something like that in the board file would eliminate this issue. It would also allow to detect bugs at compile time by refusing to compile if the board file says there is no hardware LF crystal and the sdk_config.h says there is one.

RE: NRF52 doesn't start without debugger (Jlink) on GCC toolchain

Thomas — Tue, 21 Nov 2017 15:02:38 GMT

We also did connect the debugger only after power cycling (connect to the running board) and what happens is that upon connection the board starts. that's why we are really puzzled since even before we get to hit break or otherwise stop the execution on the board, it has started normally and does what it should.

RE: NRF52 doesn't start without debugger (Jlink) on GCC toolchain

Bjørn Kvaale — Tue, 21 Nov 2017 13:41:54 GMT

Have you tried what RK has suggested? Did that help?

RE: NRF52 doesn't start without debugger (Jlink) on GCC toolchain

RK — Tue, 21 Nov 2017 07:04:36 GMT

have you tried power cycling the board and THEN plugging the JLink in. JLink can be connected to a running board. Hit break. Where are you?