NRF52832 physical pin analogRead

RE: NRF52832 physical pin analogRead

lavande — Wed, 10 Apr 2019 05:13:23 GMT

Hi Matt,

I also try this sample, but I do not how the result counts. Are there any alogrithm about the sample?

The code segemnt is the followings:

void saadc_callback(nrf_drv_saadc_evt_t const *p_event)
{
   if (p_event->type == NRF_DRV_SAADC_EVT_DONE) {
       ret_code_t err_code;

       err_code = nrf_drv_saadc_buffer_convert(p_event->data.done.p_buffer, SAMPLES_IN_BUFFER);
       APP_ERROR_CHECK(err_code);

       int i;
       NRF_LOG_INFO("ADC event number: %d", (int)m_adc_evt_counter);

       for (i = 0; i < SAMPLES_IN_BUFFER; i++) {
           NRF_LOG_INFO("%d", p_event->data.done.p_buffer[i]);
       }
        NRF_LOG_INFO(" voltage: %d\n", nrfx_saadc_buffer_convert(nrf_saadc_buffer_pointer_get(),SAMPLES_IN_BUFFER));
       m_adc_evt_counter++;
   }
}

void saadc_init(void)
{
   ret_code_t err_code;
   nrf_saadc_channel_config_t channel_config_0 = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE( NRF_SAADC_INPUT_AIN0);

   nrf_saadc_channel_config_t channel_config_1 = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE( NRF_SAADC_INPUT_AIN1);
   err_code = nrf_drv_saadc_init(NULL, saadc_callback);
   APP_ERROR_CHECK(err_code);

   err_code = nrf_drv_saadc_channel_init(0, &channel_config_0);
   APP_ERROR_CHECK(err_code);

   err_code = nrf_drv_saadc_channel_init(1, &channel_config_1);
   APP_ERROR_CHECK(err_code);

   err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[0], SAMPLES_IN_BUFFER);
   APP_ERROR_CHECK(err_code);

   err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[1], SAMPLES_IN_BUFFER);
   APP_ERROR_CHECK(err_code);

}

void saadc_stop()
{
    nrf_drv_timer_disable(&m_timer);
    nrf_drv_timer_uninit(&m_timer);
    nrf_drv_ppi_channel_disable(m_ppi_channel);
    nrf_drv_ppi_uninit();
    nrf_drv_saadc_abort();
    nrf_drv_saadc_uninit();
    while(nrf_drv_saadc_is_busy());
}

And here is the results printed out:
/**

RE: NRF52832 physical pin analogRead

AmbystomaLabs — Mon, 06 Nov 2017 16:45:06 GMT

Mike, as Matt mentioned please spend the time to learn C. You will get a lot more out of the product and you will likely find more help and resources available to you.

To help you out, I added code to my answer below that should clarify what you need to do. Cheers!

RE: NRF52832 physical pin analogRead

Matt — Sun, 05 Nov 2017 22:15:06 GMT

Not very understandable??? Are you familiar with C programming? Is it possible to share your code sample with us mortals here?

RE: NRF52832 physical pin analogRead

MikeLemon — Sun, 05 Nov 2017 19:25:49 GMT

Yes and the expected voltage is 0 also how is it possible to change the channel read in the example?

Not very understandable sins it comes in a fashion of pointers and structs with unfamilier functions.

RE: NRF52832 physical pin analogRead

MikeLemon — Sun, 05 Nov 2017 19:00:23 GMT

Yeah said that in AmbystomaLabs answer but still having issues.

RE: NRF52832 physical pin analogRead

Matt — Sun, 05 Nov 2017 18:59:59 GMT

Have you probed the pin to verify it is indeed 0V? I'm sure the saadc works as I use it to monitor the output voltage level (and yes, that's also around 2.8v) of a Telit GSM module.

RE: NRF52832 physical pin analogRead

Matt — Sun, 05 Nov 2017 18:58:57 GMT

I doubt you can re-map the analog input pin; there are 4 or 6 of them, I could not remember... you need to consult with Nordic tech support on this one.

RE: NRF52832 physical pin analogRead

MikeLemon — Sun, 05 Nov 2017 17:13:21 GMT

after some more digging I understood(Kind of got reminded) that the channels can't be enforced to another pins and the correspond to this pinout: infocenter.nordicsemi.com/index.jsp

But still doesn't solve the mystery of getting the wrong reading after debugging the example shorting it to ground NOR to VDD helps.

RE: NRF52832 physical pin analogRead

MikeLemon — Sun, 05 Nov 2017 16:22:59 GMT

Doesn't realy answers my question I'm trying to figure out how to edit one of the example codes to give me a voltage reading from say pin P0.03 and get the value into a buffer named say "VoltageBuffer"

RE: NRF52832 physical pin analogRead

AmbystomaLabs — Sun, 05 Nov 2017 16:07:10 GMT

Same as what was noted above by Matt, this is part of the channel configure. The definitions are part of the SAADC driver library and you will find them in any project that utilizes the SAADC. But here are the definitions for your reference:

/**
 * @brief Macro for setting @ref nrf_saadc_channel_config_t to default settings
 *        in single ended mode.
 *
 * @param PIN_P Analog input.
 */
#define NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(PIN_P) \
{                                                      \
    .resistor_p = NRF_SAADC_RESISTOR_DISABLED,         \
    .resistor_n = NRF_SAADC_RESISTOR_DISABLED,         \
    .gain       = NRF_SAADC_GAIN1_6,                   \
    .reference  = NRF_SAADC_REFERENCE_INTERNAL,        \
    .acq_time   = NRF_SAADC_ACQTIME_10US,              \
    .mode       = NRF_SAADC_MODE_SINGLE_ENDED,         \
    .pin_p      = (nrf_saadc_input_t)(PIN_P),          \
    .pin_n      = NRF_SAADC_INPUT_DISABLED             \
}

/**
 * @brief Macro for setting @ref nrf_saadc_channel_config_t to default settings
 *        in differential mode.
 *
 * @param PIN_P Positive analog input.
 * @param PIN_N Negative analog input.
 */
#define NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_DIFFERENTIAL(PIN_P, PIN_N) \
{                                                                       \
    .resistor_p = NRF_SAADC_RESISTOR_DISABLED,                          \
    .resistor_n = NRF_SAADC_RESISTOR_DISABLED,                          \
    .gain       = NRF_SAADC_GAIN1_6,                                    \
    .reference  = NRF_SAADC_REFERENCE_INTERNAL,                         \
    .acq_time   = NRF_SAADC_ACQTIME_10US,                               \
    .mode       = NRF_SAADC_MODE_DIFFERENTIAL,                          \
    .pin_p      = (nrf_saadc_input_t)(PIN_P),                           \
    .pin_n      = (nrf_saadc_input_t)(PIN_N)                            \
}

Here is the same stuff in the API reference on the Nordic website: infocenter.nordicsemi.com/index.jsp

If you need help in making sense of the code, in the below code I pulled the channel_config struct into the init so you can easily edit the config info. Also, it has been set to 0.4 and VDD/4 reference. This code was done in SDK12.2 but the saadc doesn't change much so you can probably use it in any SDK.

#include "nrf_drv_saadc.h"

#define SAMPLES_IN_BUFFER 1               //Number of SAADC samples in RAM before returning a SAADC event. 


static nrf_saadc_value_t m_buffer_pool[2][SAMPLES_IN_BUFFER];

void saadc_callback(nrf_drv_saadc_evt_t const * p_event) 
	{ 
		uint32_t pin_sample;

if (p_event->type == NRF_DRV_SAADC_EVT_DONE)
{
    ret_code_t err_code;
    err_code = nrf_drv_saadc_buffer_convert(p_event->data.done.p_buffer, SAMPLES_IN_BUFFER);
    APP_ERROR_CHECK(err_code);

    for (int i = 0; i < SAMPLES_IN_BUFFER; i++)
    {
                pin_sample = p_event->data.done.p_buffer[i]>>2;
    }

//At this point your pin level is captured in pin_sample. You can do whatever you want with it now

nrf_drv_saadc_uninit(); //Turns off SAADC
    NRF_SAADC->INTENCLR = (SAADC_INTENCLR_END_Clear << SAADC_INTENCLR_END_Pos);
    NVIC_ClearPendingIRQ(SAADC_IRQn);

}
}

void saadc_init(void)
{ 
	ret_code_t err_code; 
	
//Just look up the options on the enumerations in the reference info, product spec or in nrf_drv_saadc.h
	nrf_saadc_channel_config_t channel_config = {                                                  \
        .resistor_p = NRF_SAADC_RESISTOR_DISABLED,     \
        .resistor_n = NRF_SAADC_RESISTOR_DISABLED,     \
        .gain       = NRF_SAADC_GAIN1_6,               \
        .reference  = NRF_SAADC_REFERENCE_VDD4,    \
        .acq_time   = NRF_SAADC_ACQTIME_10US,          \
        .mode       = NRF_SAADC_MODE_SINGLE_ENDED,     \
        .burst      = NRF_SAADC_BURST_DISABLED,        \
        .pin_p      = NRF_SAADC_INPUT_AIN2,      \
        .pin_n      = NRF_SAADC_INPUT_DISABLED         \
    };
	
	err_code = nrf_drv_saadc_init(NULL, saadc_callback); 
	APP_ERROR_CHECK(err_code);

err_code = nrf_drv_saadc_channel_init(0, &channel_config);
APP_ERROR_CHECK(err_code);

err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[0],SAMPLES_IN_BUFFER);
APP_ERROR_CHECK(err_code);

err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[1],SAMPLES_IN_BUFFER);
APP_ERROR_CHECK(err_code);

}



//Finally this is the function you would call to start a saadc sample session

void start_saadc(void)

{ 
saadc_init(); 
nrf_drv_saadc_sample(); 
}

RE: NRF52832 physical pin analogRead

MikeLemon — Sun, 05 Nov 2017 15:59:30 GMT

Yeah I'm always learning with the info center and nrf_drv_saadc_channel_init is just initializing the channel in the IC internally and I'm looking to see how to hook it up to a pin, or maybe I got the Idea wrong and it's somehow proportional to the pin any how I couldn't find the function nrf_drv_saadc_channel_init in the example and the macro that has something to do with pins according to the infocenter"NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE"

RE: NRF52832 physical pin analogRead

Matt — Sun, 05 Nov 2017 15:26:43 GMT

Try nrf_drv_saadc_channel_init(); there is also documentation in the SAADC section in the infocenter.

RE: NRF52832 physical pin analogRead

MikeLemon — Sun, 05 Nov 2017 15:02:54 GMT

No I just don't understand how this example work like where is the line of code that configs P0.02 pin to analog channel 1 anyways when debugging and shorting the pin to ground the precise result values remains unchanged (2.8 around) instead of the expected 0V

RE: NRF52832 physical pin analogRead

Matt — Sun, 05 Nov 2017 14:59:06 GMT

Don't understand your response here. Are you saying the module you are sampling does not share the same GND as the nRF52832? Are these two not on the same PCB?

RE: NRF52832 physical pin analogRead

MikeLemon — Sun, 05 Nov 2017 14:48:31 GMT

Yes I did quite scary for a beginner like me just trying to get a reading in relation to ground but still didn't see any relation to the physical pin 0.02 in the code .

RE: NRF52832 physical pin analogRead

Matt — Sun, 05 Nov 2017 14:33:07 GMT

Have you looked into the saadc example in ~\nRF5_SDK_12.2.0_f012efa\examples\peripheral\saadc\main.c ?