RE: How to configure IO pin as analog input

atune — Tue, 17 Nov 2015 20:14:31 GMT

For reference:

nRF51822 Product Specification:
2.1 Block Diagram
2.2 Pin assignments and functions
4.14 Analog to Digital Converter (ADC)
nRF51822 Reference Manual:
14 General-Purpose Input/Output (GPIO)
31 Analog to Digital Converter (ADC)
ADC HAL

So did you check out the ADC HAL Example which is /examples/peripheral/adc_simple in the SDK? Here's also an example of reading from two inputs 'simultaneously' (without nrf adc driver).

In the SDK example, input is selected with:

nrf_adc_input_select(NRF_ADC_CONFIG_INPUT_2);

and that's about it. Triggering a conversion reads the analog value from the selected input pin.

From the reference manual:

Other peripherals in the system can attach themselves to GPIO pins and override their output value and configuration, or read their analog or digital input value ...

With the nRF you don't need to explicitly configure the pins unless you wish to use them as digital GPIO. Just configure the ADC and your pin is good to go.