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GitHub Repository: Ardupilot/ardupilot
 Path: blob/master/libraries/AP_BattMonitor/AP_BattMonitor_FuelLevel_PWM.cpp
Views: 1798
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#include "AP_BattMonitor_config.h"

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#if AP_BATTERY_FUELLEVEL_PWM_ENABLED

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#include <AP_HAL/AP_HAL.h>

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#include "AP_BattMonitor_FuelLevel_PWM.h"

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/*

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  "battery" monitor for liquid fuel level systems that give a PWM value indicating quantity of remaining fuel.

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  Output is:

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    - mAh remaining is fuel level in millilitres

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    - consumed mAh is in consumed millilitres

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    - fixed 1.0v voltage

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 */

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extern const AP_HAL::HAL& hal;

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/// Constructor

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AP_BattMonitor_FuelLevel_PWM::AP_BattMonitor_FuelLevel_PWM(AP_BattMonitor &mon, AP_BattMonitor::BattMonitor_State &mon_state, AP_BattMonitor_Params &params) :

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    AP_BattMonitor_Analog(mon, mon_state, params)

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{

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    _state.voltage = 1.0; // show a fixed voltage of 1v

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    // need to add check

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    _state.healthy = false;

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}

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/*

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  read - read the "voltage" and "current"

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*/

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void AP_BattMonitor_FuelLevel_PWM::read()

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{

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    if (!pwm_source.set_pin(_curr_pin, "FuelLevelPWM")) {

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        _state.healthy = false;

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        return;

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    }

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    uint16_t pulse_width = pwm_source.get_pwm_us();

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    /*

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      this driver assumes that CAPACITY is set to tank volume in millilitres.

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     */

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    const uint16_t pwm_empty = 1100;

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    const uint16_t pwm_full = 1900;

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    const uint16_t pwm_buffer = 20;

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    uint32_t now_us = AP_HAL::micros();

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    // check for invalid pulse

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    if (pulse_width <= (pwm_empty - pwm_buffer)|| pulse_width >= (pwm_full + pwm_buffer)) {

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        _state.healthy = (now_us - _state.last_time_micros) < 250000U;

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        return;

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    }

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    pulse_width = constrain_int16(pulse_width, pwm_empty, pwm_full);

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    float proportion_full = (pulse_width - pwm_empty) / float(pwm_full - pwm_empty);

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    float proportion_used = 1.0 - proportion_full;

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    _state.last_time_micros = now_us;

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    _state.healthy = true;

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    // map consumed_mah to consumed millilitres

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    _state.consumed_mah = proportion_used * _params._pack_capacity;

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    // map consumed_wh using fixed voltage of 1

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    _state.consumed_wh = _state.consumed_mah;

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}

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#endif  // AP_BATTERY_FUELLEVEL_PWM_ENABLED

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