Hi, I have a simple voltage divider circuit and I am measuring analog input from in between the resistors. I am using a custom NRF52832 being powered by a DK. I get quite a lot of variation in the analog values with values varying in a range of 10 and quite often I get a spike as you can see in the image the values generally are between 470 to 480 and then I even get a 489. Can you tell me what could be the issue here. Why are the values not constant or at max should be a small variation. Here is my code and the analog values over RTT.
/* Copyright (c) 2014 Nordic Semiconductor. All Rights Reserved.
*
* The information contained herein is property of Nordic Semiconductor ASA.
* Terms and conditions of usage are described in detail in NORDIC
* SEMICONDUCTOR STANDARD SOFTWARE LICENSE AGREEMENT.
*
* Licensees are granted free, non-transferable use of the information. NO
* WARRANTY of ANY KIND is provided. This heading must NOT be removed from
* the file.
*
*/
/** @file
* @defgroup nrf_adc_example main.c
* @{
* @ingroup nrf_adc_example
* @brief ADC Example Application main file.
*
* This file contains the source code for a sample application using ADC.
*
* @image html example_board_setup_a.jpg "Use board setup A for this example."
*/
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include "nrf.h"
#include "nrf_drv_saadc.h"
#include "boards.h"
#include "app_error.h"
#include "nrf_delay.h"
#include "app_util_platform.h"
#include <string.h>
#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"
#define SAMPLES_IN_BUFFER 1
#define UART_TX_BUF_SIZE 256 /**< UART TX buffer size. */
#define UART_RX_BUF_SIZE 1 /**< UART RX buffer size. */
int val=0;
static void log_init(void)
{
ret_code_t err_code = NRF_LOG_INIT(NULL);
APP_ERROR_CHECK(err_code);
NRF_LOG_DEFAULT_BACKENDS_INIT();
}
static nrf_saadc_value_t m_buffer[SAMPLES_IN_BUFFER];
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);
val = p_event->data.done.p_buffer[0];
}
}
void saadc_init(void)
{
ret_code_t err_code;
nrf_saadc_channel_config_t channel_config
= NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN0);
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, SAMPLES_IN_BUFFER);
APP_ERROR_CHECK(err_code);
}
/**
* @brief Function for main application entry.
*/
int main(void)
{
log_init();
saadc_init();
while (1)
{
nrf_drv_saadc_sample();
NRF_LOG_INFO("%d\n", val);
NRF_LOG_FLUSH();
nrf_delay_ms(100);
}
}
/** @} */
