ardupilot/libraries/AP_BattMonitor/AP_BattMonitor_Analog.cpp

#include <AP_HAL/AP_HAL.h>
#include <AP_Common/AP_Common.h>
#include <AP_Math/AP_Math.h>
#include "AP_BattMonitor_Analog.h"

extern const AP_HAL::HAL& hal;

const AP_Param::GroupInfo AP_BattMonitor_Analog::var_info[] = {

    // @Param: VOLT_PIN
    // @DisplayName: Battery Voltage sensing pin
    // @Description: Sets the analog input pin that should be used for voltage monitoring.
    // @Values: -1:Disabled, 2:Pixhawk/Pixracer/Navio2/Pixhawk2_PM1, 5:Navigator, 13:Pixhawk2_PM2/CubeOrange_PM2, 14:CubeOrange, 16:Durandal, 100:PX4-v1
    // @User: Standard
    // @RebootRequired: True
    AP_GROUPINFO("VOLT_PIN", 1, AP_BattMonitor_Analog, _volt_pin, AP_BATT_VOLT_PIN),

    // @Param: CURR_PIN
    // @DisplayName: Battery Current sensing pin
    // @Description: Sets the analog input pin that should be used for current monitoring.
    // @Values: -1:Disabled, 3:Pixhawk/Pixracer/Navio2/Pixhawk2_PM1, 4:CubeOrange_PM2/Navigator, 14:Pixhawk2_PM2, 15:CubeOrange, 17:Durandal, 101:PX4-v1
    // @User: Standard
    // @RebootRequired: True
    AP_GROUPINFO("CURR_PIN", 2, AP_BattMonitor_Analog, _curr_pin, AP_BATT_CURR_PIN),

    // @Param: VOLT_MULT
    // @DisplayName: Voltage Multiplier
    // @Description: Used to convert the voltage of the voltage sensing pin (@PREFIX@VOLT_PIN) to the actual battery's voltage (pin_voltage * VOLT_MULT). For the 3DR Power brick with a Pixhawk, this should be set to 10.1. For the Pixhawk with the 3DR 4in1 ESC this should be 12.02. For the PX using the PX4IO power supply this should be set to 1.
    // @User: Advanced
    AP_GROUPINFO("VOLT_MULT", 3, AP_BattMonitor_Analog, _volt_multiplier, AP_BATT_VOLTDIVIDER_DEFAULT),

    // @Param: AMP_PERVLT
    // @DisplayName: Amps per volt
    // @Description: Number of amps that a 1V reading on the current sensor corresponds to. With a Pixhawk using the 3DR Power brick this should be set to 17. For the Pixhawk with the 3DR 4in1 ESC this should be 17.
    // @Units: A/V
    // @User: Standard
    AP_GROUPINFO("AMP_PERVLT", 4, AP_BattMonitor_Analog, _curr_amp_per_volt, AP_BATT_CURR_AMP_PERVOLT_DEFAULT),

    // @Param: AMP_OFFSET
    // @DisplayName: AMP offset
    // @Description: Voltage offset at zero current on current sensor
    // @Units: V
    // @User: Standard
    AP_GROUPINFO("AMP_OFFSET", 5, AP_BattMonitor_Analog, _curr_amp_offset, 0),

    AP_GROUPEND
};

/// Constructor
AP_BattMonitor_Analog::AP_BattMonitor_Analog(AP_BattMonitor &mon,
                                             AP_BattMonitor::BattMonitor_State &mon_state,
                                             AP_BattMonitor_Params &params) :
    AP_BattMonitor_Backend(mon, mon_state, params)
{
    AP_Param::setup_object_defaults(this, var_info);
    _state.var_info = var_info;
    
    _volt_pin_analog_source = hal.analogin->channel(_volt_pin);
    _curr_pin_analog_source = hal.analogin->channel(_curr_pin);

    // always healthy
    _state.healthy = true;
}

// read - read the voltage and current
void
AP_BattMonitor_Analog::read()
{
    // this copes with changing the pin at runtime
    _volt_pin_analog_source->set_pin(_volt_pin);

    // get voltage
    _state.voltage = _volt_pin_analog_source->voltage_average() * _volt_multiplier;

    // read current
    if (has_current()) {
        // calculate time since last current read
        uint32_t tnow = AP_HAL::micros();
        float dt = tnow - _state.last_time_micros;

        // this copes with changing the pin at runtime
        _curr_pin_analog_source->set_pin(_curr_pin);

        // read current
        _state.current_amps = (_curr_pin_analog_source->voltage_average() - _curr_amp_offset) * _curr_amp_per_volt;

        // update total current drawn since startup
        if (_state.last_time_micros != 0 && dt < 2000000.0f) {
            // .0002778 is 1/3600 (conversion to hours)
            float mah = _state.current_amps * dt * 0.0000002778f;
            _state.consumed_mah += mah;
            _state.consumed_wh  += 0.001f * mah * _state.voltage;
        }

        // record time
        _state.last_time_micros = tnow;
    }
}

/// return true if battery provides current info
bool AP_BattMonitor_Analog::has_current() const
{
    return ((AP_BattMonitor::Type)_params._type.get() == AP_BattMonitor::Type::ANALOG_VOLTAGE_AND_CURRENT);
}