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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 755 | killagreg | 1 | #include <avr/io.h> |
| 782 | killagreg | 2 | #include <stdlib.h> |
| 765 | killagreg | 3 | #include "fc.h" |
| 4 | #include "timer0.h" |
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| 782 | killagreg | 5 | #include "uart.h" |
| 755 | killagreg | 6 | |
| 7 | int32_t PWMHeading = -1; |
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| 8 | uint8_t PWMTimeout = 0; |
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| 9 | |||
| 10 | /*********************************************/ |
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| 11 | /* Initialize Interface to CMPS02 Compass */ |
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| 12 | /*********************************************/ |
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| 13 | void CMPS03_Init(void) |
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| 14 | { |
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| 764 | killagreg | 15 | // Port PC4 connected to PWM output from compass module |
| 755 | killagreg | 16 | DDRC &= ~(1<<DDC4); // set as input |
| 764 | killagreg | 17 | PORTC |= (1<<PORTC4); // pull up to increase PWM counter also if nothing is connected |
| 755 | killagreg | 18 | |
| 19 | PWMTimeout = 0; |
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| 20 | } |
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| 21 | |||
| 22 | |||
| 23 | /*********************************************/ |
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| 24 | /* Get Data from CMPS03 */ |
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| 25 | /*********************************************/ |
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| 26 | void CMPS03_Update(void) // called every 102.4 us by timer 0 ISR |
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| 27 | { |
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| 28 | static uint16_t PWMCount = 0; |
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| 29 | // The pulse width varies from 1ms (0°) to 36.99ms (359.9°) |
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| 30 | // in other words 100us/° with a +1ms offset. |
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| 31 | // The signal goes low for 65ms between pulses, |
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| 32 | // so the cycle time is 65mS + the pulse width. |
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| 33 | // The pulse is generated by a 16 bit timer in the processor |
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| 34 | // giving a 1uS resolution, however I would not recommend |
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| 35 | // measuring this to anything better than 0.1° (10uS). |
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| 36 | |||
| 37 | if(PINC & (1<<PINC4)) |
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| 38 | { // If PWM signal is high increment PWM high counter |
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| 39 | // This counter is incremented by a periode of 102.4us, |
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| 40 | // i.e. the resoluton of pwm coded heading is approx. 1 deg. |
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| 41 | PWMCount++; |
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| 782 | killagreg | 42 | // pwm overflow? |
| 43 | if (PWMCount > 400) |
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| 44 | { |
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| 45 | if(PWMTimeout ) PWMTimeout--; // decrement timeout |
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| 46 | PWMCount = 0; // reset PWM Counter |
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| 47 | } |
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| 48 | |||
| 755 | killagreg | 49 | } |
| 50 | else // PWM is low |
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| 51 | { |
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| 52 | if((PWMCount) && (PWMCount < 400)) |
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| 53 | { |
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| 785 | killagreg | 54 | if(PWMCount <9) PWMHeading = 0; |
| 790 | killagreg | 55 | else PWMHeading = ((uint32_t)(PWMCount - 9) * 1049L)/1024; // correct timebase and offset |
| 755 | killagreg | 56 | PWMTimeout = 12; // if 12 periodes long no valid PWM was detected the data are invalid |
| 57 | // 12 * 400 counts * 102.4 us = 419 ms |
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| 58 | } |
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| 59 | PWMCount = 0; // reset pwm counter |
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| 60 | } |
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| 61 | } |
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| 62 | |||
| 63 | |||
| 64 | /*********************************************/ |
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| 65 | /* Calculate north direction (heading) */ |
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| 66 | /*********************************************/ |
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| 67 | int16_t CMPS03_Heading(void) |
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| 68 | { |
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| 765 | killagreg | 69 | int16_t heading, w, v; |
| 782 | killagreg | 70 | |
| 755 | killagreg | 71 | if(PWMTimeout) |
| 765 | killagreg | 72 | { |
| 73 | w = abs(IntegralPitch / 512); |
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| 74 | v = abs(IntegralRoll / 512); |
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| 75 | if(v > w) w = v; // get maximum declination |
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| 783 | killagreg | 76 | // if declination is small enough to have valid compass heading |
| 765 | killagreg | 77 | if(w < 35) |
| 78 | { |
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| 79 | // range from 0 to 359 |
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| 80 | heading = (int16_t)PWMHeading; |
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| 81 | if (heading < 0) heading += 360; |
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| 82 | heading = heading%360; |
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| 83 | } |
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| 782 | killagreg | 84 | else // compass to much tilted |
| 765 | killagreg | 85 | { |
| 86 | heading = -1; |
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| 87 | } |
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| 755 | killagreg | 88 | } |
| 89 | else // no data from compass |
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| 90 | { |
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| 782 | killagreg | 91 | if(!BeepTime) BeepTime = 100; // make noise to signal the compass problem |
| 755 | killagreg | 92 | heading = -1; |
| 93 | } |
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| 94 | return heading; |
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| 95 | } |