I'm having some (minor) trouble with a board based on an NRF52840 that I want to start running as soon as power is applied...
This is built using a RAK5010 board, but using custom firmware, the firmware uses an S340 softdevice.
Reading these forums it seems the general consensus is that once power is applied to the nrf52 then it should start executing, and the only similar discussions I could see were related to devices not being ready during power up and needing a delay or where the reset pin was incorrectly configured, neither is the case here.
The RAK5010 has an nrf52840 and a BG96 GPS module on board, the board has two switches one RST connected to the NRF reset pin (using pin 18) and a PWR connected to the BG96 chip.
The behaviour I have is when power is applied nothing executes until the power button is used to turn on the BG96, at which point the NRF starts executing my code four seconds later.
On the schematic there's no connection from the power button to the NRF it is purely connected through the BG96, I can't see how/why any of the other connected pins would trigger the startup but clearly that must be the case.
So.... I wanted to understand the boot process and logic with a softdevice to try to work out if I have anything incorrectly configured during my install/flash that would be causing this and or what I can/or should change to fix this behaviour.
Is there any configuration that is flashed that can define what pins cause a startup? or alternatively is there any configuration that sets the board to *not* start executing unless a pin is toggled?
I can share my code since it will be opensource (albeit the full program is rather large) but I see this same behaviour if I compile any of the NRF SDK example program.