Hi,
I am trying to use an SAADC converter to measure voltage in range from 0v to 3v5 but I cannot succeed. It is not possible to measure a voltage above 3V1. Well at least it is not possible to get reliable results.
I am using SDK15.3 and PCA10040 with nrf52832.
To replicate my problem you can run SAADC example from Nordic SDK. When you will increase a voltage on P02 PIN displayed value will increase accordingly. However when value will be above 3v2 read "raw" adc values from easyDMA will decrease. These values for voltage 3v2 are lower than for 3v1.
I studied a documentation and I've noticed that voltage on a PIN cannot be higher than VDD. So I have powered PCA10040 with external source with ~3v7 what result on VDD PIN with a value below 3v6. Next I logged measured values to SD card and I red results. I observe the same faulty behaviour.
It thought that when SAADC is configured with internal reference, single ended input (grounded negative input), and a gain of 1/6 the input range will be: Input range = (0.6 V)/(1/6) = 3.6 V. Apparently it is not. May you please me know what I am doing wrong?
