0,0 → 1,88 |
#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" |
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uint8_t PWMTimeout = 12; |
ToMk3Mag_t ToMk3Mag; |
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/*********************************************/ |
/* 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 |
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PWMTimeout = 0; |
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ToMk3Mag.CalState = 0; |
ToMk3Mag.Orientation = 1; |
} |
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/*********************************************/ |
/* 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. |
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// 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 |
} |
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} |
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 |
} |
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if(!PWMTimeout) |
{ |
if(CheckDelay(BeepDelay)) |
{ |
if(!BeepTime) BeepTime = 100; // make noise with 10Hz to signal the compass problem |
BeepDelay = SetDelay(100); |
} |
} |
} |
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