ardupilot/libraries/APM_RC/APM_RC.h

#ifndef __APM_RC_H__
#define __APM_RC_H__


#include <inttypes.h>


// Radio channels

// Note channels are from 0!

#define CH_1 0
#define CH_2 1
#define CH_3 2
#define CH_4 3
#define CH_5 4
#define CH_6 5
#define CH_7 6
#define CH_8 7
#define CH_9 8
#define CH_10 9
#define CH_11 10


#define NUM_CHANNELS 8
#define MIN_CHANNELS 5      // for ppm sum we allow less than 8 channels to make up a valid packet



class Arduino_Mega_ISR_Registry;

class APM_RC_Class

{

public:

    virtual void            Init( Arduino_Mega_ISR_Registry * isr_reg ) = 0;
    virtual void            OutputCh(uint8_t ch, uint16_t pwm) = 0;
    virtual uint16_t        OutputCh_current(uint8_t ch) = 0;
    virtual uint16_t        InputCh(uint8_t ch) = 0;
    virtual uint8_t         GetState() = 0;
    virtual void            clearOverride(void) = 0;
    virtual void            Force_Out() = 0;
    virtual void            SetFastOutputChannels( uint32_t channelmask, uint16_t speed_hz = 400 ) = 0;
    virtual void            enable_out(uint8_t) = 0;
    virtual void            disable_out(uint8_t) = 0;

    virtual void            Force_Out0_Out1(void) = 0;
    virtual void            Force_Out2_Out3(void) = 0;
    virtual void            Force_Out6_Out7(void) = 0;

    // get the approximate time of the last radio ppm update
	// - resolution of the return time in ms is defined by how often get_last_update() is called
	// - _ppm_count is modified by interrupt, but type is volatile uint8_t making it atomic for reading and writting outside the interrupt
    virtual uint32_t        get_last_update() {
        static uint32_t _last_update_time = millis(); // Initialize with current time to prevent false trigger

		// PPM refresh?
		if( _ppm_count > 0) {
			// Reset _ppm_count
			_ppm_count = 0;

			// Approximate time (very much so)  of last update
			_last_update_time = millis();
		}
		
        return _last_update_time;
    };

protected:
    uint16_t                _map_speed(uint16_t speed_hz) {
        return 2000000UL / speed_hz;
    }
    static volatile uint8_t         _ppm_count; // Modified by interrupt

};



#include "APM_RC_APM1.h"
#include "APM_RC_APM2.h"


#endif