Taking ADC readings from P0.14 and P0.15

[JustWalt]

Hello,

I'm using the nRF9160 DK for a datalogger with LTE capability, and I'm using the Arduino shield "Mux Shield II" which can be found here:
mayhewlabs.com/.../mux-shield-2

I'm trying to take analog readings from pins P0.14-P0.16. Unfortunately, only P0.16 gives readings that make any sort of sense, as P0.14 and P0.15 only give readings of ~200 and ~1500, respectively, with resolution set to 12 bits, no matter what the actual input voltage is. What's the point of an ADC that can only read one value?

It seems that most examples have you take readings from P0.13, which is also functional, but will not work for the project I need to use this board for.

Any help would be greatly appreciated!

[run_ar]

Hi,

Can you check if you could be affected one of the erratas? https://www.nordicsemi.com/DocLib/Content/Errata/nRF9160_EngA/latest/ERR/nRF9160/EngineeringA/latest/err_160

[JustWalt]

Hmm, interesting. I tried the workaround, decreasing the VDD_GPIO to 1.8V using SW11. However, the board still reads values of 200 and 1500 for pins P0.14 and P0.15, no matter the input voltage.

[hmolesworth]

I was just looking at this; the nRF52 has to be correctly controlling the FET DPDT switches (mux), which it may be but wotrth checking:

For example, P0.15 requires nRF52_P1.12 to be low (U7 switch) or set as input,and also nRF52_P0.13 must be high (U5 switch)