NFC pins as output pins do not output on flash, but do on HW reset?

[Boris Matešin]

HI,

the solution I'm working on requires quite a few IO pins, so once I ran out of regular GPIO pins I had to resort to using NFC ones.

I changed the UICR registers and rebooted the device to make sure the NFC pins are instead treated as GPIOs.

However, their behaviour is a bit unusual. After I flash the new softdevice and firmware, after the GPIO configure process (first setting default config, then output config), the two pins remain in the off state and do not react to direct set, toggle and clear commands.

After I perform a hardware reset the pins behave the opposite, first both becoming active (both should normally remain off until manually set), and then they start properly reacting to set, toggle and clear!

Any suggestions what might be the issue here?

[Nguyen Hoan Hoang]

By the default the system_nrf52.c initializes the pins as NFC. You need to change it too.

[Jørgen Holmefjord]

You can define CONFIG_NFCT_PINS_AS_GPIOS in your C\C++ preprocessor symbols to configure NFC pins for GPIO usage.

[Boris Matešin]

Thanks, that file contains the CONFIG_NFC_PING_AS_GPIOS mentioned above which may be just what I need. I'll try to insert it into the build process and see if it works.

[Boris Matešin]

Thank you, that was at least part of the solution. The other problem was that GPIOTE does not allow configuration of output pins with a pulldown, whereas GPIO still does, and switching that particular pin to GPIO solved the issue. I'm not sure whether this feature is something Nordic should care to propagate to the GPIOTE, but it sounds as if they should.