RE: AIN2: Switch between ADC and LPCOMP, AIN4: Battery

R. Kawajiri — Wed, 30 Sep 2015 08:12:47 GMT

I did not understand here.

The higher of the two input voltages will be input to both LPCOMP and ADC.

Now, it is very clear. Thank you.

RE: AIN2: Switch between ADC and LPCOMP, AIN4: Battery

Stefan Birnir Sverrisson — Wed, 30 Sep 2015 07:46:38 GMT

You observation is as expected. The LPCOMP and ADC share the MUX for the analog input pin, therefore you can not configure LPCOMP and ADC on an analog pin at the same time. In the linked thread, what I observed is that you can monitor the supply votlage of the chip with the ADC while using the LPCOMP at the same time on an analog input pin. To monitor the supply voltage with the ADC, you need to configure it as in this example, i.e. with

/* Configure ADC - set reference input source to internal 1.2V bandgap */
NRF_ADC->CONFIG = (ADC_CONFIG_REFSEL_VBG << ADC_CONFIG_REFSEL_Pos);
/* Configure ADC - set input source to VDD/3 */
NRF_ADC->CONFIG |= (ADC_CONFIG_INPSEL_SupplyOneThirdPrescaling << ADC_CONFIG_INPSEL_Pos);

Note: you may need to use another syntax to configure the ADC in the same way if you use the nrf_adc driver in the latest nRF51 SDK.