Hi there. I really love all the help and support this forum gives, especially compared to others. So thank you for taking the time to read this.
I have a custom PCB that I have designed and it works great. I am using an nRF52810 and the SAADC example (given below for reference):
/**
* Copyright (c) 2014 - 2018, Nordic Semiconductor ASA
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form, except as embedded into a Nordic
* Semiconductor ASA integrated circuit in a product or a software update for
* such product, must reproduce the above copyright notice, this list of
* conditions and the following disclaimer in the documentation and/or other
* materials provided with the distribution.
*
* 3. Neither the name of Nordic Semiconductor ASA nor the names of its
* contributors may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* 4. This software, with or without modification, must only be used with a
* Nordic Semiconductor ASA integrated circuit.
*
* 5. Any software provided in binary form under this license must not be reverse
* engineered, decompiled, modified and/or disassembled.
*
* THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
* OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
* GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
/** @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 5
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++)
{
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_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_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();
}
}
/** @} */
My code is *slightly* different, as I am using UART printf() instead of logging the ADC value to a file - but it's pretty much the same.
Anyway, I find this code pretty confusing. I understand there is an initilisation function, a timer setup function, and a callback function which is triggered or something when the timer is called. But the code within each function is very confusing to me but I am keen to understand it better.I just wanted help on three minor parts:
- 1. Extending the example to use 7 of the analogue input channels (AIN0 to AIN6)
- 2. Using scanning mode to make this as fast as possible (I think the datasheet says if multiple channels are initialised this is enabled automatically anyway - am I correct?)
- 3. Making the sampling rate per channel 1kS/s (which corresponds to sampling 7 channels every 12ms) or faster. The datasheet says it should be able to do up to 200kS/s so I hope this isn't asking too much. I don't need to print the data at this rate, but at least be able to check (if adcValue > 500 then print for example)
I have attempted this already with the following code changes, basically just guessing:
void saadc_callback(nrf_drv_saadc_evt_t const * p_event)
{
/* SAADC Event is finished - read the channels */
if (p_event->type == NRF_DRV_SAADC_EVT_DONE)
{
/* Get ADC readings */
nrf_drv_saadc_buffer_convert(p_event->data.done.p_buffer, SAMPLES_IN_BUFFER);
/* Print determined values */
printf("Channel 0: %d\r\n", p_event->data.done.p_buffer[0]);
printf("Channel 1: %d\r\n", p_event->data.done.p_buffer[1]);
printf("Channel 2: %d\r\n", p_event->data.done.p_buffer[2]);
printf("Channel 3: %d\r\n", p_event->data.done.p_buffer[3]);
printf("Channel 4: %d\r\n", p_event->data.done.p_buffer[4]);
printf("Channel 5: %d\r\n", p_event->data.done.p_buffer[5]);
printf("Channel 6: %d\r\n\r\n", p_event->data.done.p_buffer[6]);
/* Not sure what this does */
m_adc_evt_counter++;
if (m_adc_evt_counter == 7)
{
m_adc_evt_counter = 0;
}
/* Toggle LED */
//nrf_gpio_pin_toggle(LED_PIN_NUMBER);
}
}
void saadc_init(void)
{
/* Create the configuration structs for all channels */
nrf_saadc_channel_config_t channel_0_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN0);
nrf_saadc_channel_config_t channel_1_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN1);
nrf_saadc_channel_config_t channel_2_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN2);
nrf_saadc_channel_config_t channel_3_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN3);
nrf_saadc_channel_config_t channel_4_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN4);
nrf_saadc_channel_config_t channel_5_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN5);
nrf_saadc_channel_config_t channel_6_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN6);
/* Initialise the SAADC peripheral */
nrf_drv_saadc_init(NULL, saadc_callback);
/* Initialise all channels */
nrf_drv_saadc_channel_init(0, &channel_0_config);
nrf_drv_saadc_channel_init(1, &channel_1_config);
nrf_drv_saadc_channel_init(2, &channel_2_config);
nrf_drv_saadc_channel_init(3, &channel_3_config);
nrf_drv_saadc_channel_init(4, &channel_4_config);
nrf_drv_saadc_channel_init(5, &channel_5_config);
nrf_drv_saadc_channel_init(6, &channel_6_config);
/* Not sure what this does */
nrf_drv_saadc_buffer_convert(m_buffer_pool[0], SAMPLES_IN_BUFFER);
nrf_drv_saadc_buffer_convert(m_buffer_pool[1], SAMPLES_IN_BUFFER);
nrf_drv_saadc_buffer_convert(m_buffer_pool[2], SAMPLES_IN_BUFFER);
nrf_drv_saadc_buffer_convert(m_buffer_pool[3], SAMPLES_IN_BUFFER);
nrf_drv_saadc_buffer_convert(m_buffer_pool[4], SAMPLES_IN_BUFFER);
nrf_drv_saadc_buffer_convert(m_buffer_pool[5], SAMPLES_IN_BUFFER);
nrf_drv_saadc_buffer_convert(m_buffer_pool[6], SAMPLES_IN_BUFFER);
}
void timer_handler(nrf_timer_event_t event_type, void * p_context)
{
/* Not sure what this is */
}
void saadc_sampling_event_enable(void)
{
nrf_drv_ppi_channel_enable(m_ppi_channel);
}
void saadc_sampling_event_init(void)
{
/* Initialise PPI */
nrf_drv_ppi_init();
/* Set the configuration struct to a default timer */
nrf_drv_timer_config_t timer_cfg = NRF_DRV_TIMER_DEFAULT_CONFIG;
/* Customise the bit width to 32 bits */
timer_cfg.bit_width = NRF_TIMER_BIT_WIDTH_32;
/* Initialise the timer */
nrf_drv_timer_init(&m_timer, &timer_cfg, timer_handler);
/* setup m_timer for compare event every 12ms */
uint32_t ticks = nrf_drv_timer_ms_to_ticks(&m_timer, 12);
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 */
nrf_drv_ppi_channel_alloc(&m_ppi_channel);
nrf_drv_ppi_channel_assign(m_ppi_channel,
timer_compare_event_addr,
saadc_sample_task_addr);
}
However, this did not really work and gave some weird output results. So I must be doing something wrong. Things like what SAMPLES_IN_BUFFER should be or what it means, or what m_adc_evt_counter means and what its importance is, or what nrf_drv_saadc_buffer_convert(m_buffer_pool[<Channel Number>], SAMPLES_IN_BUFFER); does exactly for each channel.
I know this is a big question but it should be a simple concept - just utilising the ADC on more channels, and at a faster rate. So I hope someone can help and I really appreciate if so!
Thanks for your time reading! :)
