batt_custom_avr.h

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/**
 * @file batt_custom_avr.h
 *
 * Custom battery monitor with an AVR "co-processor" over I2C
 */

#pragma once

#include <lib/drivers/smbus/SMBus.hpp>
#include <perf/perf_counter.h>
#include <px4_platform_common/module.h>
#include <px4_platform_common/param.h>
#include <px4_platform_common/i2c_spi_buses.h>
#include <uORB/topics/battery_status.h>

#include <board_config.h>

using namespace time_literals;


class BatteryCustomAvr : public device::I2C, public I2CSPIDriver<BatteryCustomAvr>
{
public:
    BatteryCustomAvr(const I2CSPIDriverConfig &config);

    ~BatteryCustomAvr();

    int init();

    static I2CSPIDriverBase *instantiate(const I2CSPIDriverConfig &config,
                         int runtime_instance);
    static void print_usage();

    void RunImpl();

    /**
     * default address for the avr mcu, no deeper reason, set your own if you want
     * this needs to be in the public part so the main function can access it
     */
    const static uint8_t I2C_DEFAULT_ADDRESS = 0x4;

private:
    /**
     * the reported battery value is the average of the last values,
     * to remove outliers
     */
    constexpr static uint8_t AVERAGE_VALUES = 3;
    float last_values_V[AVERAGE_VALUES];
    uint8_t last_values_counter = 0;

    /**
     * how often to poll the device: the adc runs with more than 10 kHz,
     * but there is no need to waste I2C time and AVR cycles
     */
    constexpr static auto POLLING_INVERVALL = 500_ms;

    orb_advert_t battery_topic;

    /** register address for battery value */
    const uint8_t BATTERY_REGISTER = 0x1;

    /** voltage range for the adc values */
    constexpr static float VOLTAGE_RANGE = 5.0;
    constexpr static uint8_t CELL_COUNT = 1;

    // just to be safe, here are some default values for 1S lipos
    constexpr static float LOW_V = 3.6;
    constexpr static float CRITICAL_V = 3.5;
    constexpr static float EMERGENCY_V = 3.2;

};