Subversion Repositories FlightCtrl

#include <avr/io.h>
#include <stdlib.h>
#include <inttypes.h>
#include "timer0.h"
#include "uart.h"
#include "fc.h"
#include "rc.h"
#include "eeprom.h"
#include "mk3mag.h"

uint8_t PWMTimeout = 12;
ToMk3Mag_t ToMk3Mag;


/*********************************************/
/*  Initialize Interface to MK3MAG Compass   */
/*********************************************/
void MK3MAG_Init(void)
{
        // Port PC4 connected to PWM output from compass module
        DDRC &= ~(1<<DDC4); // set as input
        PORTC |= (1<<PORTC4); // pull up  to increase PWM counter also if nothing is connected

        PWMTimeout = 0;

        ToMk3Mag.CalState = 0;
        ToMk3Mag.Orientation = 1;
}


/*********************************************/
/*  Get PWM from MK3MAG                      */
/*********************************************/
void MK3MAG_Update(void) // called every 102.4 us by timer 0 ISR
{
        static uint16_t PWMCount = 0;
        static uint16_t BeepDelay = 0;
        // The pulse width varies from 1ms (0°) to 36.99ms (359.9°)
        // in other words 100us/° with a +1ms offset.
        // The signal goes low for 65ms between pulses,
        // so the cycle time is 65mS + the pulse width.

        // pwm is high
        if(PINC & (1<<PINC4))
        {       // If PWM signal is high increment PWM high counter
                // This counter is incremented by a periode of 102.4us,
                // i.e. the resoluton of pwm coded heading is approx. 1 deg.
                PWMCount++;
                // pwm overflow?
                if (PWMCount > 400)
                {
                        if(PWMTimeout) PWMTimeout--; // decrement timeout
                        CompassHeading = -1; // unknown heading
                        PWMCount = 0; // reset PWM Counter
                }

        }
        else // pwm is low
        {   // ignore pwm values values of 0 and higher than 37 ms
                if((PWMCount) && (PWMCount < 362)) // 362 * 102.4us = 37.0688 ms
                {
                        if(PWMCount <10) CompassHeading = 0;
                        else CompassHeading = ((uint32_t)(PWMCount - 10) * 1049L)/1024; // correct timebase and offset
                        CompassOffCourse = ((540 + CompassHeading - CompassCourse) % 360) - 180;
                        PWMTimeout = 12; // if 12 periodes long no valid PWM was detected the data are invalid
                        // 12 * 362 counts * 102.4 us
                }
                else
                {  // bad pwm value (out of range or permanent low)
                        if(PWMTimeout) PWMTimeout--; // decrement timeout
                        CompassHeading = -1; // unknown heading
                        CompassOffCourse = 0;
                }
                PWMCount = 0; // reset pwm counter
        }

        if(!PWMTimeout)
        {
                if(CheckDelay(BeepDelay))
                {
                        if(!BeepTime) BeepTime = 100; // make noise with 10Hz to signal the compass problem
                        BeepDelay = SetDelay(100);
                }
        }
}