Subversion Repositories FlightCtrl

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

uint8_t PWMTimeout = 12;
// This will updated in interrupt handler. Should not be processed by main, other than just atomic copy.
volatile uint16_t volatileMagneticHeading;
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_periodicTask(void) {// called every 102.4 us by timer 0 ISR
        static uint16_t PWMCount = 0;
        static uint16_t beepDelay = 0;
        // static uint16_t debugCounter = 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 (debugCounter++ == 5000) {
    // DebugOut.Digital[0] ^= DEBUG_MK3MAG;
        // debugCounter = 0;
        // }

        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
                        volatileMagneticHeading = -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)
                          volatileMagneticHeading = 0;
                        else {
                          volatileMagneticHeading = ((uint32_t) (PWMCount - 10) * 1049L) / 1024; // correct timebase and offset
                                //DebugOut.Digital[1] ^= DEBUG_MK3MAG; // correct signal recd.
                        }
                        /*
                         compassHeading - compassCourse on a -180..179 range.
                         compassHeading 20 compassCourse 30 --> ((540 - 10)%360) - 180 = -10
                         compassHeading 30 compassCourse 20 --> ((540 + 10)%360) - 180 = 10
                         compassHeading 350 compassCourse 10 --> ((540 + 340)%360) - 180 = -20
                         compassHeading 10 compassCourse 350 --> ((540 - 340)%360) - 180 = 20
                         */
                        //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
                }
                PWMCount = 0; // reset pwm counter
        }

        if (!PWMTimeout) {
                if (checkDelay(beepDelay)) {
                        if (!beepTime)
                                beep(50); // make noise with 10Hz to signal the compass problem
                        beepDelay = setDelay(100);
                }
        }
}