| 0,0 → 1,95 |
|---|
| #include <avr/io.h> |
| #include <stdlib.h> |
| #include "fc.h" |
| #include "timer0.h" |
| #include "uart.h" |
| |
| int32_t PWMHeading = -1; |
| uint8_t PWMTimeout = 0; |
| |
| /*********************************************/ |
| /* Initialize Interface to CMPS02 Compass */ |
| /*********************************************/ |
| void CMPS03_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; |
| } |
| |
| |
| /*********************************************/ |
| /* Get Data from CMPS03 */ |
| /*********************************************/ |
| void CMPS03_Update(void) // called every 102.4 us by timer 0 ISR |
| { |
| static uint16_t PWMCount = 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. |
| // The pulse is generated by a 16 bit timer in the processor |
| // giving a 1uS resolution, however I would not recommend |
| // measuring this to anything better than 0.1° (10uS). |
| |
| 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 |
| PWMCount = 0; // reset PWM Counter |
| } |
| |
| } |
| else // PWM is low |
| { |
| if((PWMCount) && (PWMCount < 400)) |
| { |
| if(PWMCount <9) PWMHeading = 0; |
| else PWMHeading = ((uint32_t)(PWMCount - 9) * 1049L)/1024; // correct timebase and offset |
| PWMTimeout = 12; // if 12 periodes long no valid PWM was detected the data are invalid |
| // 12 * 400 counts * 102.4 us = 419 ms |
| } |
| PWMCount = 0; // reset pwm counter |
| } |
| } |
| |
| |
| /*********************************************/ |
| /* Calculate north direction (heading) */ |
| /*********************************************/ |
| int16_t CMPS03_Heading(void) |
| { |
| int16_t heading, w, v; |
| |
| if(PWMTimeout) |
| { |
| w = abs(IntegralPitch / 512); |
| v = abs(IntegralRoll / 512); |
| if(v > w) w = v; // get maximum declination |
| // if declination is small enough to have valid compass heading |
| if(w < 35) |
| { |
| // range from 0 to 359 |
| heading = (int16_t)PWMHeading; |
| if (heading < 0) heading += 360; |
| heading = heading%360; |
| } |
| else // compass to much tilted |
| { |
| heading = -1; |
| } |
| } |
| else // no data from compass |
| { |
| if(!BeepTime) BeepTime = 100; // make noise to signal the compass problem |
| heading = -1; |
| } |
| return heading; |
| } |