Hi,
Does nRF52832 use normal ADC input to detect battery level (ex. AIN0, AIN1...)? or nRF52832 have other method to do this job?
Thank you,
Chianglin
Hi,
Does nRF52832 use normal ADC input to detect battery level (ex. AIN0, AIN1...)? or nRF52832 have other method to do this job?
Thank you,
Chianglin
Hi,
If you need a consistent sampling frequency for the sensor, then the simplest is to sample the battery also every time. This is demonstrated by this minimal modification to the SDK 15.3 SAADC example:
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/** @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 <string.h>
#include "nrf.h"
#include "nrf_drv_saadc.h"
#include "nrf_drv_ppi.h"
#include "nrf_drv_timer.h"
#include "boards.h"
#include "app_error.h"
#include "nrf_delay.h"
#include "app_util_platform.h"
#include "nrf_pwr_mgmt.h"
#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"
#define SAMPLES_IN_BUFFER 2 // Number of channels in this case
volatile uint8_t state = 1;
static const nrf_drv_timer_t m_timer = NRF_DRV_TIMER_INSTANCE(0);
static nrf_saadc_value_t m_buffer_pool[2][SAMPLES_IN_BUFFER];
static nrf_ppi_channel_t m_ppi_channel;
static uint32_t m_adc_evt_counter;
void timer_handler(nrf_timer_event_t event_type, void * p_context)
{
}
void saadc_sampling_event_init(void)
{
ret_code_t err_code;
err_code = nrf_drv_ppi_init();
APP_ERROR_CHECK(err_code);
nrf_drv_timer_config_t timer_cfg = NRF_DRV_TIMER_DEFAULT_CONFIG;
timer_cfg.bit_width = NRF_TIMER_BIT_WIDTH_32;
err_code = nrf_drv_timer_init(&m_timer, &timer_cfg, timer_handler);
APP_ERROR_CHECK(err_code);
/* setup m_timer for compare event every 400ms */
uint32_t ticks = nrf_drv_timer_ms_to_ticks(&m_timer, 400);
nrf_drv_timer_extended_compare(&m_timer,
NRF_TIMER_CC_CHANNEL0,
ticks,
NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK,
false);
nrf_drv_timer_enable(&m_timer);
uint32_t timer_compare_event_addr = nrf_drv_timer_compare_event_address_get(&m_timer,
NRF_TIMER_CC_CHANNEL0);
uint32_t saadc_sample_task_addr = nrf_drv_saadc_sample_task_get();
/* setup ppi channel so that timer compare event is triggering sample task in SAADC */
err_code = nrf_drv_ppi_channel_alloc(&m_ppi_channel);
APP_ERROR_CHECK(err_code);
err_code = nrf_drv_ppi_channel_assign(m_ppi_channel,
timer_compare_event_addr,
saadc_sample_task_addr);
APP_ERROR_CHECK(err_code);
}
void saadc_sampling_event_enable(void)
{
ret_code_t err_code = nrf_drv_ppi_channel_enable(m_ppi_channel);
APP_ERROR_CHECK(err_code);
}
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++)
{
if (i == 0)
{
NRF_LOG_INFO("Sensor reading: %d", p_event->data.done.p_buffer[i]);
}
else if (i == 1)
{
NRF_LOG_INFO("Battery reading: %d", p_event->data.done.p_buffer[i]);
}
else
{
NRF_LOG_ERROR("Use only two samples per buffer with this setup.");
}
}
m_adc_evt_counter++;
}
}
void saadc_init(void)
{
ret_code_t err_code;
// Init SAADC driver
err_code = nrf_drv_saadc_init(NULL, saadc_callback);
APP_ERROR_CHECK(err_code);
// Init sensor channel
nrf_saadc_channel_config_t channel_config_sensor =
NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN0);
err_code = nrf_drv_saadc_channel_init(0, &channel_config_sensor);
APP_ERROR_CHECK(err_code);
// Init battery channel
nrf_saadc_channel_config_t channel_config_battery =
NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_VDD);
err_code = nrf_drv_saadc_channel_init(1, &channel_config_battery);
APP_ERROR_CHECK(err_code);
// Start conversion
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);
}
/**
* @brief Function for main application entry.
*/
int main(void)
{
uint32_t err_code = NRF_LOG_INIT(NULL);
APP_ERROR_CHECK(err_code);
NRF_LOG_DEFAULT_BACKENDS_INIT();
ret_code_t ret_code = nrf_pwr_mgmt_init();
APP_ERROR_CHECK(ret_code);
saadc_init();
saadc_sampling_event_init();
saadc_sampling_event_enable();
NRF_LOG_INFO("SAADC HAL simple example started.");
while (1)
{
nrf_pwr_mgmt_run();
NRF_LOG_FLUSH();
}
}
/** @} */
Running the application () gives you this log output:
<info> app: SAADC HAL simple example started. <info> app: ADC event number: 0 <info> app: Sensor reading: 6 <info> app: Battery reading: 626 <info> app: ADC event number: 1 <info> app: Sensor reading: 19 <info> app: Battery reading: 626 <info> app: ADC event number: 2 <info> app: Sensor reading: 22 <info> app: Battery reading: 627 <info> app: ADC event number: 3 ...
Note that you can increase the sampling frequency by adjusting line 97, where you can also replace nrf_drv_timer_ms_to_ticks() with nrf_drv_timer_us_to_ticks() if you need to provide the sampling interval in microseconds.
Alternatively, you can sample only the sensor most of the time, then us an app timer to reconfigure the saadc to sample the battery once in a while, before reverting to sampling only the sensor. This will probably be a more power-efficient way (at least if you don't sample the battery often), but will potentially give you a short pause in the sensor sampling which may or may not be acceptable.
I want to use two ADC at the same time
Hopefully it has become clear by now, but the nRF52832 only has one ADC.
To measure multiple inputs, you have to multiplex them to the one ADC.
See the block diagram in the Product Specification:
Thank you for your support.
I will merge into my program and test it.
Thank you
