Simple analog read on nrf52

[Remo]

Hello. How i can do a simple read an 0 -> 3 Volt (vdd) signal on Analog 0 P0.03? I try it with saadc without sucess

            int result = 0;
		
			NRF_SAADC->CH[0].CONFIG = (
						SAADC_CH_PSELN_PSELN_AnalogInput0 << SAADC_CH_CONFIG_BURST_Pos |
						SAADC_CH_CONFIG_BURST_Enabled << SAADC_CH_CONFIG_BURST_Pos |
						SAADC_CH_CONFIG_MODE_SE << SAADC_CH_CONFIG_MODE_Pos |
						SAADC_CH_CONFIG_TACQ_10us << SAADC_CH_CONFIG_TACQ_Pos |
						SAADC_CH_CONFIG_REFSEL_Internal << SAADC_CH_CONFIG_TACQ_Pos |
						SAADC_CH_CONFIG_GAIN_Gain1_5 << SAADC_CH_CONFIG_GAIN_Pos |
						SAADC_CH_CONFIG_RESN_Bypass << SAADC_CH_CONFIG_RESN_Pos |
						SAADC_CH_CONFIG_RESP_Bypass << SAADC_CH_CONFIG_RESP_Pos );

			NRF_SAADC->CH[0].PSELP = SAADC_CH_PSELP_PSELP_VDD;
			NRF_SAADC->CH[0].PSELN = SAADC_CH_PSELN_PSELN_NC;
		
			// Configure the SAADC resolution.
			NRF_SAADC->RESOLUTION = SAADC_RESOLUTION_VAL_14bit << SAADC_RESOLUTION_VAL_Pos;
			NRF_SAADC->OVERSAMPLE = SAADC_OVERSAMPLE_OVERSAMPLE_Over256x << SAADC_OVERSAMPLE_OVERSAMPLE_Pos;

			//Setup memory location
			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;

			// Enable SAADC (would capture analog pins if they were used in CH[0].PSELP)
			NRF_SAADC->ENABLE = SAADC_ENABLE_ENABLE_Enabled << SAADC_ENABLE_ENABLE_Pos;

[Remo]

...mmmh maybe i am completely wrong, but i try the code on the example without an result i get an result on the varaible "result" this result is about 12000 and changes +/- 10 on every round.

int main(void)
{
  uint32_t err_code;
  bool erase_bonds;
	__WFE();
  // Initialize.
//APP_TIMER_INIT(APP_TIMER_PRESCALER, APP_TIMER_OP_QUEUE_SIZE, false);
//uart_init();

//buttons_leds_init(&erase_bonds);
//ble_stack_init();
//    gap_params_init();
//    services_init();
//    advertising_init();
//    conn_params_init();

//    printf("\r\nUART Start!\r\n");
//    err_code = ble_advertising_start(BLE_ADV_MODE_FAST);
//    APP_ERROR_CHECK(err_code);



// Enter main loop.
for (;;)
{
			//#define EX1_COUNT 5
			//float ex1_result_f[EX1_COUNT];
			//int16_t ex1_result[EX1_COUNT];
    //power_manage();
			//read_right_hand_keys();

			volatile int16_t result = 0;
			volatile float precise_result = 0;

			// Start HFCLK from crystal oscillator, this will give the SAADC higher accuracy
			NRF_CLOCK->TASKS_HFCLKSTART = 1;
			while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0);
			NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;

			// 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;

			// Enable SAADC (would capture analog pins if they were used in CH[0].PSELP)
			NRF_SAADC->ENABLE = SAADC_ENABLE_ENABLE_Enabled << SAADC_ENABLE_ENABLE_Pos;

			// Calibrate the SAADC (only needs to be done once in a while)
			NRF_SAADC->TASKS_CALIBRATEOFFSET = 1;
			while (NRF_SAADC->EVENTS_CALIBRATEDONE == 0);
			NRF_SAADC->EVENTS_CALIBRATEDONE = 0;
			while (NRF_SAADC->STATUS == (SAADC_STATUS_STATUS_Busy <<SAADC_STATUS_STATUS_Pos));

			// Start the SAADC and wait for the started event.
			NRF_SAADC->TASKS_START = 1;
			while (NRF_SAADC->EVENTS_STARTED == 0);
			NRF_SAADC->EVENTS_STARTED = 0;

			// Do a SAADC sample, will put the result in the configured RAM buffer.
			NRF_SAADC->TASKS_SAMPLE = 1;
			while (NRF_SAADC->EVENTS_END == 0);
			NRF_SAADC->EVENTS_END = 0;

			// Convert the result to voltage
			// Result = [V(p) - V(n)] * GAIN/REFERENCE * 2^(RESOLUTION)
			// Result = (VDD - 0) * ((1/6) / 0.6) * 2^14
			// VDD = Result / 4551.1
			precise_result = (float)result / 4551.1f;
			precise_result; // to get rid of set but not used warning

			// Stop the SAADC, since it's not used anymore.
			NRF_SAADC->TASKS_STOP = 1;
			while (NRF_SAADC->EVENTS_STOPPED == 0);
			NRF_SAADC->EVENTS_STOPPED = 0;
		
		

		

}