And I confirm that, when plugging in my micro-USB cable into the “nRF USB“ port and setting the “nRF Power Source“ switch to “USB“, I see the LEDs “turning“ (i.e. the program is running) but very dim
I only have a single USB cable, so I don’t have the main USB power plugged in; I’m pretty sure that wouldn’t change the power source of the nRF.
Notes about UICR
Of course, register REGOUT0 is non-volatile, i.e. it is part of the UICR registers which are mapped to a flash page, so its contents stays even after power cycling the board. If a different program was run which write a different value to REGOUT0 , the board would be running at a different voltage.
The recommended behavior of the scum-programmer is:
when started, check the value of REGOUT0
if different that the default value 7, write 7 and soft-reset
the board will then reboot at 1.8V
The user doesn’t have to worry about this, but should only plug in SCuM once she confirms the LEDs are dim
About Said’s technique
@Said Alvarado-Marin 's technique is to provide add the following to flash_placement.xml
In essence, this while technique just writes the REGOUT0 register. Using this super convoluted approach allows the program to change the voltage without touching the C code, which is useful if you have compile C code which isn’t yours and you want to change the voltage. But this technique is by no means AFAICT needed. I’d like to get input from @Said Alvarado-Marin on this.
Also, I don’t understand why we use the setting to 1 (2.1V) and not 0 or 7 (1.8V). Again, would like input from @Said Alvarado-Marin .