ardupilot/libraries/AP_EPM/AP_EPM.h

// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-

/*
 * AP_EPM.h
 *
 *  Created on: DEC 06, 2013
 *      Author: Andreas Jochum
 *
 *      Set-up Wiki: http://copter.ardupilot.com/wiki/common-electro-permanent-magnet-gripper/
 */

/// @file	AP_EPM.h
/// @brief	AP_EPM control class
#pragma once

#include <AP_Math/AP_Math.h>
#include <AP_Common/AP_Common.h>
#include <RC_Channel/RC_Channel.h>

// EPM PWM definitions
#define EPM_GRAB_PWM_DEFAULT        1900
#define EPM_RELEASE_PWM_DEFAULT     1100
#define EPM_NEUTRAL_PWM_DEFAULT     1500
#define EPM_RETURN_TO_NEUTRAL_MS    500         // EPM PWM returns to neutral position this many milliseconds after grab or release
#define EPM_REGRAB_DEFAULT          0           // default re-grab interval (in seconds) to ensure cargo is securely held

/// @class	AP_EPM
/// @brief	Class to manage the EPM_CargoGripper 
class AP_EPM {
public:
    AP_EPM();

    // initialise the EPM
    void        init();

    // enabled - true if the EPM is enabled
    bool        enabled() { return _enabled; }

    // grab - move the EPM pwm output to the grab position
    void        grab();

    // release - move the EPM pwm output to the release position
    void        release();

    // update - moves the pwm back to neutral after the timeout has passed
    // should be called at at least 10hz
    void        update();

    static const struct AP_Param::GroupInfo        var_info[];

private:

    // neutral - return the EPM pwm output to the neutral position
    void        neutral();

    // EPM flags
    struct EPM_Flags {
        uint8_t grab    : 1;    // true if we think we have grabbed onto cargo, false if we think we've released it
        uint8_t active  : 1;    // true if we are actively sending grab or release PWM to EPM to activate grabbing or releasing, false if we are sending neutral pwm
    } _flags;

    // parameters
    AP_Int8     _enabled;               // EPM enable/disable
    AP_Int16    _grab_pwm;              // PWM value sent to EPM to initiate grabbing the cargo
    AP_Int16    _release_pwm;           // PWM value sent to EPM to release the cargo
    AP_Int16    _neutral_pwm;           // PWM value sent to EPM when not grabbing or releasing
    AP_Int8     _regrab_interval;       // Time in seconds that gripper will regrab the cargo to ensure grip has not weakend

    // internal variables
    uint32_t    _last_grab_or_release;
};