Setting SPI pins to values that are OOB of the g_ADigitalPinMap[] array causes OOB reads. This variant.h has pin 0 as 0xFF which passes through as NRFX_SPIM_PIN_NOT_USED.
The NRF52 undervoltage bootlock feature implemented behind
NRF52_POWER_MANAGEMENT was introduced in v1.12.
It configures a fixed voltage level of 3.3V and prevents the software
from booting if the battery voltage is below that level.
This is problematic for various reasons. The most important one being
that it breaks devices that use cell chemistries other than Li-Ion,
such as LFP, LTO or SIB which have much lower minimum voltages.
As a quick fix to prevent devices from failing, disable the feature
until it has been decided how to handle this in the future and a
proper implementation has been provided.
Signed-off-by: Frieder Schrempf <frieder@fris.de>
Frieder Schrempf