reading analog through UART

RE: reading analog through UART

awneil — Thu, 08 Nov 2018 10:48:08 GMT

[quote userid="74966" url="~/f/nordic-q-a/40164/reading-analog-through-uart/156464"]Yes, I finally figured it out[/quote]

Excellent.

So please Verify the answer:

[quote userid="74966" url="~/f/nordic-q-a/40164/reading-analog-through-uart/156464"]the result from the ADC does not correspond to what I was expecting[/quote]

That's really a separate question - so would be better in a new thread.

RE: reading analog through UART

t_m — Thu, 08 Nov 2018 10:30:34 GMT

Yes, I finally figured it out, except that the result from the ADC does not correspond to what I was expecting. I was trying to read voltage from a DC power source but the results do not much. If I am allowed , I would like to share my code here so that somebody can point me out what I am missing there.

** @file
 * @defgroup uart_example_main main.c
 * @{
 * @ingroup uart_example
 * @brief UART Example Application main file.
 *
 * This file contains the source code for a sample application using UART.
 *
 */

#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include "app_uart.h"
#include "nrf_drv_saadc.h"
#include "app_error.h"
#include "nrf_delay.h"
#include "nrf.h"
#include "bsp.h"
#include "nrf_log.h"
#if defined (UART_PRESENT)
#include "nrf_uart.h"
#endif
#if defined (UARTE_PRESENT)
#include "nrf_uarte.h"
#endif


//#define ENABLE_LOOPBACK_TEST  /**< if defined, then this example will be a loopback test, which means that TX should be connected to RX to get data loopback. */

#define MAX_TEST_DATA_BYTES     (15U)                /**< max number of test bytes to be used for tx and rx. */
#define UART_TX_BUF_SIZE 256                         /**< UART TX buffer size. */
#define UART_RX_BUF_SIZE 256                         /**< UART RX buffer size. */
#define UART_HWFC APP_UART_FLOW_CONTROL_DISABLED
#define NRF_LOG_ERROR(...)                     NRF_LOG_INTERNAL_ERROR(__VA_ARGS__)
#define NRF_LOG_WARNING(...)                   NRF_LOG_INTERNAL_WARNING( __VA_ARGS__)
#define NRF_LOG_INFO(...)                      NRF_LOG_INTERNAL_INFO( __VA_ARGS__)
#define NRF_LOG_DEBUG(...)                     NRF_LOG_INTERNAL_DEBUG( __VA_ARGS__)
#define SAMPLES_IN_BUFFER 5
static uint32_t              m_adc_evt_counter;

void uart_error_handle(app_uart_evt_t * p_event)
{
    if (p_event->evt_type == APP_UART_COMMUNICATION_ERROR)
    {
        APP_ERROR_HANDLER(p_event->data.error_communication);
    }
    else if (p_event->evt_type == APP_UART_FIFO_ERROR)
    {
        APP_ERROR_HANDLER(p_event->data.error_code);
    }
}




/**
 * @brief Function for main application entry.
 */
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]);
        }
        m_adc_evt_counter++;
    }
}

void saadc_init(void)
{
    ret_code_t err_code;
    nrf_drv_saadc_config_t saadc_config;
    saadc_config.low_power_mode = true;
    saadc_config.resolution = NRF_SAADC_RESOLUTION_12BIT;
    saadc_config.oversample = NRF_SAADC_OVERSAMPLE_DISABLED;
    saadc_config.interrupt_priority = APP_IRQ_PRIORITY_LOW;
    nrf_saadc_channel_config_t channel_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(SAADC_CH_PSELP_PSELP_VDD);
    err_code = nrf_drv_saadc_init(&saadc_config, saadc_callback);
    APP_ERROR_CHECK(err_code);
    
    channel_config.pin_p  = NRF_SAADC_INPUT_AIN5;
  err_code = nrf_drv_saadc_channel_init(0, &channel_config);
    APP_ERROR_CHECK(err_code);
    
}


void uart_config_init(void)
{
    ret_code_t err_code;
    const app_uart_comm_params_t comm_params =
      {
          RX_PIN_NUMBER,
          TX_PIN_NUMBER,
          RTS_PIN_NUMBER,
          CTS_PIN_NUMBER,
          UART_HWFC,
          false,
          NRF_UART_BAUDRATE_115200
      };

    APP_UART_FIFO_INIT(&comm_params,
                         UART_RX_BUF_SIZE,
                         UART_TX_BUF_SIZE,
                         uart_error_handle,
                         APP_IRQ_PRIORITY_LOWEST,
                         err_code);

    APP_ERROR_CHECK(err_code);
}
int main(void)
{
    
    saadc_init();
    nrf_delay_ms(2);
    bsp_board_leds_init();
  uart_config_init();
    
    nrf_saadc_value_t AdcVal[1];
    
    //nrf_drv_saadc_sample_convert(1, &AdcVal[1]);

  printf("\r\nStart: \r\n");
    
    while(true)
    {
        nrf_drv_saadc_sample_convert(0, &AdcVal[0]);
        //int16_t voltage = 5*AdcVal[0]/4096;
        //printf("Analog reading: %u\n\r", voltage);
        printf("Analog reading: %u\n\r", AdcVal[0]);
        nrf_delay_ms(500);
    }

   /* while (true)
    
    {
        uint8_t cr;
        while (app_uart_get(&cr) != NRF_SUCCESS);
        while (app_uart_put(cr) != NRF_SUCCESS);

        if (cr == 'q' || cr == 'Q')
        {
            printf(" \r\nExit!\r\n");

            while (true)
            {
                // Do nothing.
            }
        }
    }*/

}


/** @} */

When I set the power supply voltage to 5V, the analog reading I see in the UART is about 2000. This is equivalent to 2000*5/4096 = ~2.44Volts. Any idea?

RE: reading analog through UART

Bjørn Kvaale — Wed, 07 Nov 2018 14:58:59 GMT

t_m Have you figured out this issue or do you still need some help?

RE: reading analog through UART

awneil — Mon, 05 Nov 2018 13:09:46 GMT

As noted, that's a standard 'C' thing - not specific to Nordic.

It's generally easier if you learn 'C' on a PC or similar before moving on to the added complications of embedded microcontrollers and wireless comms.

Here are some 'C' learning & reference materials - including a free online textbook:

http://blog.antronics.co.uk/2011/08/08/so-youre-thinking-of-starting-with-c/

RE: reading analog through UART

t_m — Mon, 05 Nov 2018 12:53:46 GMT

Hi owneil

Thanks for the reply. I have limited experience with C. I did not know if those errors mean that there are some missing .c files.

RE: reading analog through UART

awneil — Mon, 05 Nov 2018 12:43:37 GMT

[quote userid="74966" url="~/f/nordic-q-a/40164/reading-analog-through-uart"]I just started learning nrf52832 DK[/quote]

Do you have any prior 'C' programming experience?

[quote userid="74966" url="~/f/nordic-q-a/40164/reading-analog-through-uart"]Can somebody explain me what might cause the error[/quote]

As the messages say you have referred to those symbols, but have not defined them (the mentioned symbols are all function names - so "referring" to them probably means that you have called them).

This is usually caused by including a header file (.h) - but not adding the corresponding .c file(s) to your project.

This is a standard 'C' thing - nothing specifically to do with Nordic: http://c-faq.com/decl/decldef.html