NRF52840 repeated reboot without debugger

RE: NRF52840 repeated reboot without debugger

Sigurd — Fri, 07 Dec 2018 10:08:19 GMT

If you are entering the APP_ERROR_CHECK() with an error code, and you have DEBUG defined and logging enabled, the app_error_fault_handler() function will print the error code. In “nRF Only mode”, the debugger IC is not powered, but if you have a logic analyzer that can parse the serial data, you can just hook the analyzer up to the UART TX pin(p0.06), and see what the error code is.

[quote userid="29647" url="~/f/nordic-q-a/41100/nrf52840-repeated-reboot-without-debugger/160039"]Does this have anything to do with Watchdog?[/quote]

I don't think so.

[quote userid="29647" url="~/f/nordic-q-a/41100/nrf52840-repeated-reboot-without-debugger/160060"]* How can I use the internal HF oscillator to confirm if my external HF crystal is not the source of the problem?[/quote]

First step would be to see if you get the event EVENTS_HFCLKSTARTED when you trigger the TASKS_HFCLKSTART task.

  // Start HFCLK from crystal oscillator.
  NRF_CLOCK->TASKS_HFCLKSTART = 1;
  while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0);

[quote userid="29647" url="~/f/nordic-q-a/41100/nrf52840-repeated-reboot-without-debugger/160060"]* What are the symptoms of an unstable external HF crystal?[/quote]

You would see problems with peripherals that needs an accurate HF clock, e.g. the RADIO peripheral.

[quote userid="29647" url="~/f/nordic-q-a/41100/nrf52840-repeated-reboot-without-debugger/160060"]* What happens if my RF is feeding back through the crystal path? I have an antenna which is part of the GND plane. I am feeding the RF output to a GND pattern which acts like an antenna.[/quote]

That is OK. It should not cause any issues.

RE: NRF52840 repeated reboot without debugger

gauthamkarnik — Mon, 03 Dec 2018 16:51:12 GMT

Had a few more questions to ask

* How can I use the internal HF oscillator to confirm if my external HF crystal is not the source of the problem?
* Will the UART work satisfactorily well if I use the internal HF oscillator?
* What are the symptoms of an unstable external HF crystal?
* What happens if my RF is feeding back through the crystal path? I have an antenna which is part of the GND plane. I am feeding the RF output to a GND pattern which acts like an antenna.

RE: NRF52840 repeated reboot without debugger

gauthamkarnik — Mon, 03 Dec 2018 15:33:29 GMT

I agree with you on the DEBUG processor flag. I was just referring to the debug uart and not the flag.

Regarding the DEFAULT Mode, every thing works fine. As long as we have the JTAG communications things work fine.

Does this have anything to do with Watchdog?

RE: NRF52840 repeated reboot without debugger

Sigurd — Mon, 03 Dec 2018 15:15:33 GMT

[quote user="gauthamkarnik"]Even if the debug UART is enabled I do not suppose we could see anything when the processor resets.[/quote]

That is the reason why we add the DEBUG Processor flag, it will prevent the reset, and should instead print the error-code.

[quote user="gauthamkarnik"]* run in "nRF Only" mode[/quote]

Do you see any difference if you set it to "DEFAULT" instead?

RE: NRF52840 repeated reboot without debugger

gauthamkarnik — Mon, 03 Dec 2018 14:31:12 GMT

We do not have the debug UART enabled. I will look at the Debug Processor flag.

Even if the debug UART is enabled I do not suppose we could see anything when the processor resets.

We have also tested this on the Evaluation board (nRF52840 Eval board) and set up the board to

* run with external battery

* run in "nRF Only" mode

The behavior is similar to what we are seeing with our custom HW.

RE: NRF52840 repeated reboot without debugger

Sigurd — Mon, 03 Dec 2018 14:19:29 GMT

Hi,

A reset indicates that you are running into the error handler, where the default behavior is to do a reset.

Have you enabled UART logging, do you gey any output from the UART?

Could you set the DEBUG preprocessor flag:

Is the UART RX pin connected to anything?