I have borrowed a snippet from github nordic repository for doing a single Vdd voltage sampling. I lifted the code and installed it directly into my app. It appears to hang on calibration loop wiating for a calibrate done to occur but it never comes. Here is the code:
volatile int16_t result = 0;
volatile float precise_result = 0;
static void saadc_init(void){
bsp_board_led_on(led1);
// Configure SAADC singled-ended channel, Internal reference (0.6V) and 1/6 gain.
NRF_SAADC->CH[0].CONFIG = (SAADC_CH_CONFIG_GAIN_Gain1_6 << SAADC_CH_CONFIG_GAIN_Pos) |
(SAADC_CH_CONFIG_MODE_SE << SAADC_CH_CONFIG_MODE_Pos) |
(SAADC_CH_CONFIG_REFSEL_Internal << SAADC_CH_CONFIG_REFSEL_Pos) |
(SAADC_CH_CONFIG_RESN_Bypass << SAADC_CH_CONFIG_RESN_Pos) |
(SAADC_CH_CONFIG_RESP_Bypass << SAADC_CH_CONFIG_RESP_Pos) |
(SAADC_CH_CONFIG_TACQ_3us << SAADC_CH_CONFIG_TACQ_Pos);
// Configure the SAADC channel with VDD as positive input, no negative input(single ended).
NRF_SAADC->CH[0].PSELP = SAADC_CH_PSELP_PSELP_VDD << SAADC_CH_PSELP_PSELP_Pos;
NRF_SAADC->CH[0].PSELN = SAADC_CH_PSELN_PSELN_NC << SAADC_CH_PSELN_PSELN_Pos;
// Configure the SAADC resolution.
NRF_SAADC->RESOLUTION = SAADC_RESOLUTION_VAL_14bit << SAADC_RESOLUTION_VAL_Pos;
// Configure result to be put in RAM at the location of "result" variable.
NRF_SAADC->RESULT.MAXCNT = 1;
NRF_SAADC->RESULT.PTR = (uint32_t)&result;
// No automatic sampling, will trigger with TASKS_SAMPLE.
NRF_SAADC->SAMPLERATE = SAADC_SAMPLERATE_MODE_Task << SAADC_SAMPLERATE_MODE_Pos;
// Calibrate the SAADC
NRF_SAADC->TASKS_CALIBRATEOFFSET = 1;
while (NRF_SAADC->EVENTS_CALIBRATEDONE == 0); //IT NEVER LEAVES THIS LOOP AS EVENTS_CALIBRATEDONE APPEARS TO NEVER OCCUR
NRF_SAADC->EVENTS_CALIBRATEDONE = 0;
while (NRF_SAADC->STATUS == (SAADC_STATUS_STATUS_Busy <<SAADC_STATUS_STATUS_Pos));
}
