example_service_calibration_caching.c

This is an example on how the sensor calibration can be cached
The example executes as follows:

• Retrieve and register HAL stuct
• Create config, processing, and sensor instances
• Calibrate and prepare sensor
• Measure, read and process radar data
• Check 'calibration_needed' indication
• If needed either use cached calibration or perform new calibration and store
• Destroy sensor, processing, and config instances

// Copyright (c) Acconeer AB, 2020-2023
// All rights reserved
// This file is subject to the terms and conditions defined in the file
// 'LICENSES/license_acconeer.txt', (BSD 3-Clause License) which is part
// of this source code package.
 
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
 
#include "acc_config.h"
#include "acc_definitions_a121.h"
#include "acc_definitions_common.h"
#include "acc_hal_definitions_a121.h"
#include "acc_hal_integration_a121.h"
#include "acc_integration.h"
#include "acc_processing.h"
#include "acc_rss_a121.h"
#include "acc_sensor.h"
 
#include "acc_version.h"
 
/** \example example_service_calibration_caching.c
 * @brief This is an example on how the sensor calibration can be cached
 * @n
 * The example executes as follows:
 *   - Retrieve and register HAL stuct
 *   - Create config, processing, and sensor instances
 *   - Calibrate and prepare sensor
 *   - Measure, read and process radar data
 *   - Check 'calibration_needed' indication
 *   - If needed either use cached calibration or perform new calibration and store
 *   - Destroy sensor, processing, and config instances
 */
 
#define SENSOR_ID          (1U)
#define SENSOR_TIMEOUT_MS  (1000U)
#define MAX_DATA_ENTRY_LEN (15U) // "-32000+-32000i" + zero termination
 
/**
 * A sensor calibration is valid at the temperature it was done +- 15 degrees
 *
 * If the temperature isn't controlled during caching, which is the case in this example,
 * the maximum amount of caches needs to be calculated from a temperature difference of 16.
 *
 * For example
 * - A calibration is done at 25 degrees, which means it is valid between 10 and 40 degrees
 * - The temperature changes to 41 degrees
 * - A new calibration needs to be done at 41 degrees since it is above the valid range for the previous calibration
 * - The new calibration is then valid between 26 and 56 degrees
 *
 * However, if the temperature is controlled, for example in a factory, the maximum amount
 * of caches can be calculated from a temperature difference of 30.
 *
 * For example
 * - A calibration is done at 25 degrees, which means it is valid between 10 and 40 degrees
 * - The temperature is manually changed to 55 degrees
 * - A new calibration can be done which is valid between 40 and 70 degrees
 *
 * The maximum temperature variation that the application will operate in is assumed to be
 * -40 to 85 degrees in this example.
 */
#define MAX_CAL_TEMP_DIFF  (16)
#define MAX_TEMP_VARIATION (125)
#define MAX_CACHE_COUNT    ((MAX_TEMP_VARIATION / MAX_CAL_TEMP_DIFF) + 1)
 
// Note that each 'acc_cal_result_t' struct should be suitably aligned for any built-in type
static acc_cal_result_t cal_results[MAX_CACHE_COUNT];
static int16_t          cal_temps[MAX_CACHE_COUNT];
static uint16_t         curr_cache_count = 0;
 
static void set_config(acc_config_t *config);
 
static bool find_cache_index(int16_t temp, uint16_t *cache_index);
 
static bool get_next_empty_cache_index(uint16_t *cache_index);
 
static bool add_cache(uint16_t cache_index, int16_t temp);
 
static bool calibration_caching_and_prepare(acc_sensor_t *sensor,
                                            acc_config_t *config,
                                            void         *buffer,
                                            uint32_t      buffer_size,
                                            bool          temp_known,
                                            int16_t       temp);
 
static void cleanup(acc_config_t *config, acc_processing_t *processing, acc_sensor_t *sensor, void *buffer);
 
int acconeer_main(int argc, char *argv[]);
 
int acconeer_main(int argc, char *argv[])
{
        (void)argc;
        (void)argv;
        acc_config_t             *config      = NULL;
        acc_processing_t         *processing  = NULL;
        acc_sensor_t             *sensor      = NULL;
        void                     *buffer      = NULL;
        uint32_t                  buffer_size = 0;
        acc_processing_metadata_t proc_meta;
        acc_processing_result_t   proc_result;
 
        printf("Acconeer software version %s\n", acc_version_get());
 
        const acc_hal_a121_t *hal = acc_hal_rss_integration_get_implementation();
 
        if (!acc_rss_hal_register(hal))
        {
                return EXIT_FAILURE;
        }
 
        config = acc_config_create();
        if (config == NULL)
        {
                printf("acc_config_create() failed\n");
                cleanup(config, processing, sensor, buffer);
                return EXIT_FAILURE;
        }
 
        set_config(config);
 
        // Print the configuration
        acc_config_log(config);
 
        processing = acc_processing_create(config, &proc_meta);
        if (processing == NULL)
        {
                printf("acc_processing_create() failed\n");
                cleanup(config, processing, sensor, buffer);
                return EXIT_FAILURE;
        }
 
        if (!acc_rss_get_buffer_size(config, &buffer_size))
        {
                printf("acc_rss_get_buffer_size() failed\n");
                cleanup(config, processing, sensor, buffer);
                return EXIT_FAILURE;
        }
 
        buffer = acc_integration_mem_alloc(buffer_size);
        if (buffer == NULL)
        {
                printf("buffer allocation failed\n");
                cleanup(config, processing, sensor, buffer);
                return EXIT_FAILURE;
        }
 
        acc_hal_integration_sensor_supply_on(SENSOR_ID);
        acc_hal_integration_sensor_enable(SENSOR_ID);
 
        sensor = acc_sensor_create(SENSOR_ID);
        if (sensor == NULL)
        {
                printf("acc_sensor_create() failed\n");
                cleanup(config, processing, sensor, buffer);
                return EXIT_FAILURE;
        }
 
        if (!calibration_caching_and_prepare(sensor, config, buffer, buffer_size, false, 0))
        {
                printf("calibration_caching_and_prepare() failed\n");
                acc_sensor_status(sensor);
                cleanup(config, processing, sensor, buffer);
                return EXIT_FAILURE;
        }
 
        uint32_t update_count = 5U;
 
        for (uint32_t i = 0U; i < update_count; i++)
        {
 
                if (!acc_sensor_measure(sensor))
                {
                        printf("acc_sensor_measure failed\n");
                        acc_sensor_status(sensor);
                        cleanup(config, processing, sensor, buffer);
                        return EXIT_FAILURE;
                }
 
                if (!acc_hal_integration_wait_for_sensor_interrupt(SENSOR_ID, SENSOR_TIMEOUT_MS))
                {
                        printf("Sensor interrupt timeout\n");
                        acc_sensor_status(sensor);
                        cleanup(config, processing, sensor, buffer);
                        return EXIT_FAILURE;
                }
 
                if (!acc_sensor_read(sensor, buffer, buffer_size))
                {
                        printf("acc_sensor_read failed\n");
                        acc_sensor_status(sensor);
                        cleanup(config, processing, sensor, buffer);
                        return EXIT_FAILURE;
                }
 
                acc_processing_execute(processing, buffer, &proc_result);
 
                if (proc_result.calibration_needed)
                {
                        printf("New calibration needed due to temperature change\n");
 
                        if (!calibration_caching_and_prepare(sensor, config, buffer, buffer_size, true, proc_result.temperature))
                        {
                                printf("calibration_caching_and_prepare() failed\n");
                                acc_sensor_status(sensor);
                                cleanup(config, processing, sensor, buffer);
                                return EXIT_FAILURE;
                        }
                }
                else
                {
                        printf("IQ data retrieved\n");
                }
        }
 
        cleanup(config, processing, sensor, buffer);
 
        printf("Application finished OK\n");
 
        return EXIT_SUCCESS;
}
 
static void set_config(acc_config_t *config)
{
        // Add configuration of the sensor here
 
        acc_config_start_point_set(config, 80);
        acc_config_num_points_set(config, 160);
}
 
static bool find_cache_index(int16_t temp, uint16_t *cache_index)
{
        bool     cache_found   = false;
        uint16_t min_temp_diff = UINT16_MAX;
 
        // If caches have overlapping temperature ranges, the cache
        // with center temperature closest to 'temp' will be chosen
        for (uint16_t index = 0; index < curr_cache_count; index++)
        {
                uint16_t temp_diff = abs(cal_temps[index] - temp);
 
                if (temp_diff < MAX_CAL_TEMP_DIFF && temp_diff < min_temp_diff)
                {
                        min_temp_diff = temp_diff;
                        *cache_index  = index;
                        cache_found   = true;
                }
        }
 
        return cache_found;
}
 
static bool get_next_empty_cache_index(uint16_t *cache_index)
{
        *cache_index = curr_cache_count;
 
        return curr_cache_count < MAX_CACHE_COUNT;
}
 
static bool add_cache(uint16_t cache_index, int16_t temp)
{
        bool status = false;
 
        if ((cache_index == curr_cache_count) && (cache_index < MAX_CACHE_COUNT))
        {
                cal_temps[cache_index] = temp;
                curr_cache_count++;
                status = true;
        }
 
        return status;
}
 
static bool calibration_caching_and_prepare(acc_sensor_t *sensor,
                                            acc_config_t *config,
                                            void         *buffer,
                                            uint32_t      buffer_size,
                                            bool          temp_known,
                                            int16_t       temp)
{
        bool     status      = true;
        bool     use_cache   = false;
        uint16_t cache_index = 0;
 
        // If temperature is known, there might be a cached calibration result that can be used
        if (temp_known)
        {
                if (find_cache_index(temp, &cache_index))
                {
                        use_cache = true;
                }
        }
 
        // If no cached calibration can be used, a new calibration should be made
        // and the result stored at an empty cache_index
        if (!use_cache)
        {
                printf("New calibration is performed\n");
 
                if (!get_next_empty_cache_index(&cache_index))
                {
                        printf("No empty cache_index to store calibration result\n");
                        return false;
                }
 
                status                             = false;
                bool           cal_complete        = false;
                const uint16_t calibration_retries = 1U;
 
                // Random disturbances may cause the calibration to fail. At failure, retry at least once.
                for (uint16_t i = 0; !status && (i <= calibration_retries); i++)
                {
                        // Reset sensor before calibration by disabling/enabling it
                        acc_hal_integration_sensor_disable(SENSOR_ID);
                        acc_hal_integration_sensor_enable(SENSOR_ID);
 
                        do
                        {
                                status = acc_sensor_calibrate(sensor, &cal_complete, &cal_results[cache_index], buffer, buffer_size);
 
                                if (status && !cal_complete)
                                {
                                        status = acc_hal_integration_wait_for_sensor_interrupt(SENSOR_ID, SENSOR_TIMEOUT_MS);
                                }
                        } while (status && !cal_complete);
                }
 
                if (status)
                {
                        // Reset sensor after calibration by disabling/enabling it
                        acc_hal_integration_sensor_disable(SENSOR_ID);
                        acc_hal_integration_sensor_enable(SENSOR_ID);
 
                        acc_cal_info_t cal_info;
                        acc_sensor_get_cal_info(&cal_results[cache_index], &cal_info);
                        add_cache(cache_index, cal_info.temperature);
                }
        }
        else
        {
                printf("Using cached calibration for %u degrees Celsius\n", cal_temps[cache_index]);
        }
 
        if (status)
        {
                status = acc_sensor_prepare(sensor, config, &cal_results[cache_index], buffer, buffer_size);
        }
 
        return status;
}
 
static void cleanup(acc_config_t *config, acc_processing_t *processing, acc_sensor_t *sensor, void *buffer)
{
        acc_hal_integration_sensor_disable(SENSOR_ID);
        acc_hal_integration_sensor_supply_off(SENSOR_ID);
 
        if (sensor != NULL)
        {
                acc_sensor_destroy(sensor);
        }
 
        if (processing != NULL)
        {
                acc_processing_destroy(processing);
        }
 
        if (config != NULL)
        {
                acc_config_destroy(config);
        }
 
        if (buffer != NULL)
        {
                acc_integration_mem_free(buffer);
        }
}