POF comparator doesn't work as expected- seems to crash chip

RE: POF comparator doesn't work as expected- seems to crash chip

Stian Røed Hafskjold — Wed, 06 Nov 2019 17:00:28 GMT

Hi, I was able to reproduce the fail if I added CLOCK_ENABLED and CLOCK_CONFIG_IRQ_PRIORITY to the sdk_config. The problem is that you also need to add the clock driver source files to the project. If you only add the defines to sdk_config.h, then the clock driver is not part of the project, but the nrfx_power driver thinks it is, and sets the wrong interrupt handler. And then you get a crash.

Add these files to the project:

modules/nrfx/drivers/src/nrfx_power_clock.c
modules/nrfx/drivers/src/nrfx_clock.c

And then it will complain about missing CLOCK_CONFIG_LF_SRC. So add this to sdk_config.h:

#ifndef CLOCK_CONFIG_LF_SRC
#define CLOCK_CONFIG_LF_SRC 1 //(or 0 if you don't want to use external LF crystal)
#endif

RE: POF comparator doesn't work as expected- seems to crash chip

Thurlby — Mon, 04 Nov 2019 09:35:41 GMT

I was wondering if you had any updates on this? It's important to us to have the clock enabled (we use various sdk functions that are dependent on it), so we still can't get pof working at the moment. If we understood better what the interdependencies were we might be able to move forward.

RE: POF comparator doesn't work as expected- seems to crash chip

Thurlby — Wed, 09 Oct 2019 08:52:53 GMT

Thank you for your reply.

I've made that work using the blinky sdk_config, so then did a bit of diff reducing on my sdk_config and the blinky one and discovered that adding the lines

#ifndef CLOCK_ENABLED
#define CLOCK_ENABLED 1
#endif

#ifndef CLOCK_CONFIG_IRQ_PRIORITY
#define CLOCK_CONFIG_IRQ_PRIORITY 7
#endif

#ifndef NRFX_POWER_ENABLED
#define NRFX_POWER_ENABLED 1
#endif

#ifndef NRFX_POWER_CONFIG_IRQ_PRIORITY
#define NRFX_POWER_CONFIG_IRQ_PRIORITY 7
#endif

To the top of blinky sdk_config.h (line 50, after the setup) made it fail (specifically, toggling the clock_enabled 0,1 makes it work and fail).

This is with identical makefile to blinky blank(+ include sdk/modules/nrfx/drivers/include and src sdk/modules/nrfx/drivers/src/nrfx_power.c), identical linker, and identical sdk_config.h except for this change.

Can you explain the relationship between the clocks and the pof comparator?

RE: POF comparator doesn't work as expected- seems to crash chip

Stian Røed Hafskjold — Tue, 08 Oct 2019 10:04:48 GMT

The code you provided is working just fine here without any modifications. SDK 15.0.0, starting with blinky example, pasting your code, adding nrfx_power.h and .c to the project, and NRFX_POWER_ENABLED=1 to sdk_config.h.

LED2 turns off at 2.39V and LED4 continues blinking.

Which DK version is this?

Can you also please post the hex file so I can try it here?

RE: POF comparator doesn't work as expected- seems to crash chip

Thurlby — Mon, 30 Sep 2019 09:26:07 GMT

Thank you for your reply, I have been away so hadn't replied sooner.

You are right, I was not using that switch. However, the behaviour (other than the LED dimming) stays exactly the same if I do leave the USB attached and use the VEXT->nRF switch.

New setup:
Power over P21, USB attached, VEXT->nRF in ON position, same code as before

Behaviour:
Without the call to nrfx_power_pof_enable: blinking LED 4 (brightly) all the way down to 1.61 V, then cuts out both leds and reboots into flashing when power gets above 1.62V again.
With the line nrfx_power_pof_enable: blinking LED 4 until 2.36V, then stops blinking the led, does not turn off led 2, as the pof event handler should, and does not restart when power goes up to 3.3 again.

RE: POF comparator doesn't work as expected- seems to crash chip

Stian Røed Hafskjold — Thu, 19 Sep 2019 11:22:40 GMT

The P21 is by default powering the whole board, including the ATSAM (Segger JLink) and some IC switches. If you decrease the voltage you will get unpredictable behavior. There is a small switch (VEXT->nRF) close to the P21 header. If you put it in the ON position, the P21 will be powering the nRF directly, disconnecting the rest of the board from P21. It's important to leave the USB cable connected to power the rest of the board (VDD). Now you can control the voltage on the nRF52 through P21.

You can double check the voltage on the nRF52 by measuring on VDD_nRF on P20.

The LEDs are powered by VDD (USB) so they will not dim when the voltage on P21 is decreased, if things are setup correctly.