How do I setup an ADC channel for reading nRF52832 VDD

[John Galvin]

I have a battery operated unit & according to the data sheet I should be able to read the VDD pin

However, when I look in the nrf-saadc.h it does not have this listed

so I added it the  line "#define NRF_SAADC_VDD 9"

I tried adding it to my dts file

I initialise it without errors

but when I try to read it I get in error code -22

I did try 8 but that doesn't even initialise

[John Galvin]

Actually  channel@9 & channel@8 both fail to initialise & read.

I'm sure it was initialising with channel@9