Proximity app ADC Input

[rahul1]

I am using nRF51422 with the SDK 11.  I am using the proximity application to measure the battery service.  By default, the device uses VDD as its ADC input.  I would like to change the input to another available pin (for example p0.00).  How would I be able to do this?

[Øyvind]

Hello,

...

I assume you mean the ADC uses VDD as the ADC voltage reference?

From the Proximity Application's main.c:

/**@brief Function for configuring ADC to do battery level conversion.
 */
static void adc_configure(void)
{
    #ifdef NRF51
    ret_code_t err_code = nrf_drv_adc_init(NULL, adc_event_handler);
    APP_ERROR_CHECK(err_code);

    static nrf_drv_adc_channel_t channel = NRF_DRV_ADC_DEFAULT_CHANNEL(NRF_ADC_CONFIG_INPUT_DISABLED);
    //channel.config.config.input = NRF_ADC_CONFIG_SCALING_SUPPLY_ONE_THIRD;
    channel.config.config.input = (uint32_t)NRF_ADC_CONFIG_SCALING_SUPPLY_ONE_THIRD;
    nrf_drv_adc_channel_enable(&channel);

    err_code = nrf_drv_adc_buffer_convert(&adc_buf[0], 1);
    APP_ERROR_CHECK(err_code);
}

This is where the ADC is configured using the ADC HW driver. You must change NRF_ADC_CONFIG_INPUT_DISABLED to wanted channel.

static nrf_drv_adc_channel_t channel = NRF_DRV_ADC_DEFAULT_CHANNEL(NRF_ADC_CONFIG_INPUT_DISABLED);

More information about the ADC driver can be found here. The channels that are available for the ADC can be found here. Be aware that AIN0 (P0.00) is ADC/LPCOMP reference input. Please read the nRF51422 Reference Manual chapter 31 Analog to Digital Converter (ADC) to ensure correct usage. Please have a look at this document .

Kind regards,
Oeyvind