Simple analog read on nrf52

RE: Simple analog read on nrf52

BelvitaSoft — Tue, 23 Jul 2019 13:12:16 GMT

Ok, I also solved the problem. Pin Analog A0 is defined as P02 on the development kit, although on the bottom of the board is written that pin P3 in A0. I changed the connection and it works.🙂

RE: Simple analog read on nrf52

BelvitaSoft — Tue, 23 Jul 2019 11:33:05 GMT

Hi guys, I have the same problem - I got zero when I try to print the variable precise_result. I measure a pin 3 (A0) with voltage divider that output voltage is equal to 2.7 V. It is also confused for me that it is printed only twice, although it is in while loop.

Any advice about solving this problem? Rabe Jørgen @restoftheworld

Best regards :)

RE: Simple analog read on nrf52

Rabe — Mon, 03 Dec 2018 15:56:54 GMT

It's already fixed. Thanks

RE: Simple analog read on nrf52

Jørgen Holmefjord — Mon, 03 Dec 2018 14:25:16 GMT

Hard to know what you have done without seeing your code. Please post a new question where you described your steps and post the code/project. That way we can help you debug the issue.

RE: Simple analog read on nrf52

Rabe — Mon, 03 Dec 2018 08:05:05 GMT

Excuse me Jorgen, I used that simple code from NordicSnippets GitHub page with saadc project as background to compile and when I start the program with Segger I always get 0 as result. Any idea? Would I have to change something from sdk_config.h? I would like to read the battery level of my DK PCA10040. Thanks

RE: Simple analog read on nrf52

Jørgen Holmefjord — Mon, 27 Feb 2017 09:49:06 GMT

You are correct. The example is set to a resolution of 14 bits, and measures the VDD voltage of the board. You can change which pin is measured on line 22. The SAADC result is converted to voltage and stored in the variable precise_result.

RE: Simple analog read on nrf52

Remo — Fri, 24 Feb 2017 19:05:09 GMT

...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.

RE: Simple analog read on nrf52

Remo — Fri, 24 Feb 2017 19:04:58 GMT

what do the Task_sample? How i can find the nrf_dr_saadc ? i had only copiing the code from an sample. But i the PIC MCU world was this ADC read simpler :-)

RE: Simple analog read on nrf52

Remo — Fri, 24 Feb 2017 19:02:12 GMT

...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;
		
		

		

}

RE: Simple analog read on nrf52

Jørgen Holmefjord — Thu, 23 Feb 2017 09:42:38 GMT

Hi,

You can find an example of a simple read using the SAADC on the NordicSnippets GitHub page.

If you want to use the SAADC driver, included in the SDK, you can find a simple example in this thead.

Best regards,

Jørgen

RE: Simple analog read on nrf52

andribiotico — Thu, 23 Feb 2017 08:57:20 GMT

Correct me if I'm wrong, but I can't see "where" do you trigger the TASK_SAMPLE. Why don't you use the library "nrf_dr_saadc"? It's very easy to use