In my product I use certain GPIO pins configured as input with the pull up activated to act as sense inputs connected to momentary switches to control the application firmware.
Recently I had several incidents from my customers and fellow developers where GPIOs became irreversibly damaged.
In each case a GPIO involved was connected to a momentary switch (i.e. a mechanical switch between GPIO pin and GND).
The application worked fine until the point of breakdown, which means the GPIO was correctly configured as input with a pull-up.
After the damage the pin is stuck to GND. The devices affected have an increased current consumption (normal deep sleep current is ~150uA, which goes up to several tens of mAs for damaged chips.
In the application we use one or two momentary switches. On the one the momentary switch is depressed approx. 1% of the time in active mode. The other is depressed 10% of the time. Latter is more prone to an earlier breakdown, i.e. the degradation happens during the on state of the momentary switch, until the point of breakdown.
As using a momentary or latching switch on a GPIO is a standard use case for microcontrolllers, I would like to understand what could possible cause such damage.
The incident is unlikely related to my product and is also reproducible on a reference device (Adafruit nRF52 Bluefruit), therefore dependency on layout of board or influence of additional peripherals I can rule out at this stage.
