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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 1612 | dongfang | 1 | #include <avr/io.h> |
| 2 | #include <stdlib.h> |
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| 3 | #include <inttypes.h> |
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| 4 | #include "timer0.h" |
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| 5 | #include "eeprom.h" |
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| 6 | #include "mk3mag.h" |
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| 7 | |||
| 8 | uint8_t PWMTimeout = 12; |
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| 2051 | - | 9 | // This will updated in interrupt handler. Should not be processed by main, other than just atomic copy. |
| 10 | volatile uint16_t volatileMagneticHeading; |
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| 1969 | - | 11 | ToMk3Mag_t toMk3Mag; |
| 1612 | dongfang | 12 | |
| 13 | /*********************************************/ |
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| 14 | /* Initialize Interface to MK3MAG Compass */ |
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| 15 | /*********************************************/ |
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| 2039 | - | 16 | void MK3MAG_init(void) { |
| 1801 | - | 17 | // Port PC4 connected to PWM output from compass module |
| 18 | DDRC &= ~(1 << DDC4); // set as input |
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| 19 | PORTC |= (1 << PORTC4); // pull up to increase PWM counter also if nothing is connected |
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| 20 | PWMTimeout = 0; |
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| 2039 | - | 21 | toMk3Mag.calState = 0; |
| 22 | toMk3Mag.orientation = 1; |
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| 1612 | dongfang | 23 | } |
| 24 | |||
| 25 | /*********************************************/ |
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| 26 | /* Get PWM from MK3MAG */ |
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| 27 | /*********************************************/ |
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| 2039 | - | 28 | void MK3MAG_periodicTask(void) {// called every 102.4 us by timer 0 ISR |
| 1801 | - | 29 | static uint16_t PWMCount = 0; |
| 1887 | - | 30 | static uint16_t beepDelay = 0; |
| 2041 | - | 31 | // static uint16_t debugCounter = 0; |
| 1801 | - | 32 | // The pulse width varies from 1ms (0°) to 36.99ms (359.9°) |
| 33 | // in other words 100us/° with a +1ms offset. |
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| 34 | // The signal goes low for 65ms between pulses, |
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| 35 | // so the cycle time is 65mS + the pulse width. |
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| 36 | // pwm is high |
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| 1612 | dongfang | 37 | |
| 2041 | - | 38 | // if (debugCounter++ == 5000) { |
| 39 | // DebugOut.Digital[0] ^= DEBUG_MK3MAG; |
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| 40 | // debugCounter = 0; |
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| 41 | // } |
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| 1805 | - | 42 | |
| 1801 | - | 43 | if (PINC & (1 << PINC4)) { |
| 44 | // If PWM signal is high increment PWM high counter |
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| 45 | // This counter is incremented by a periode of 102.4us, |
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| 46 | // i.e. the resoluton of pwm coded heading is approx. 1 deg. |
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| 47 | PWMCount++; |
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| 48 | // pwm overflow? |
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| 49 | if (PWMCount > 400) { |
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| 50 | if (PWMTimeout) |
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| 51 | PWMTimeout--; // decrement timeout |
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| 2051 | - | 52 | volatileMagneticHeading = -1; // unknown heading |
| 1801 | - | 53 | PWMCount = 0; // reset PWM Counter |
| 54 | } |
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| 55 | } else { // pwm is low |
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| 1805 | - | 56 | // ignore pwm values values of 0 and higher than 37 ms; |
| 1801 | - | 57 | if ((PWMCount) && (PWMCount < 362)) { // 362 * 102.4us = 37.0688 ms |
| 58 | if (PWMCount < 10) |
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| 2051 | - | 59 | volatileMagneticHeading = 0; |
| 1805 | - | 60 | else { |
| 2051 | - | 61 | volatileMagneticHeading = ((uint32_t) (PWMCount - 10) * 1049L) / 1024; // correct timebase and offset |
| 1845 | - | 62 | //DebugOut.Digital[1] ^= DEBUG_MK3MAG; // correct signal recd. |
| 1805 | - | 63 | } |
| 64 | /* |
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| 65 | compassHeading - compassCourse on a -180..179 range. |
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| 66 | compassHeading 20 compassCourse 30 --> ((540 - 10)%360) - 180 = -10 |
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| 67 | compassHeading 30 compassCourse 20 --> ((540 + 10)%360) - 180 = 10 |
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| 68 | compassHeading 350 compassCourse 10 --> ((540 + 340)%360) - 180 = -20 |
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| 69 | compassHeading 10 compassCourse 350 --> ((540 - 340)%360) - 180 = 20 |
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| 70 | */ |
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| 71 | //compassOffCourse = ((540 + compassHeading - compassCourse) % 360) - 180; |
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| 1801 | - | 72 | PWMTimeout = 12; // if 12 periodes long no valid PWM was detected the data are invalid |
| 73 | // 12 * 362 counts * 102.4 us |
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| 74 | } |
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| 75 | PWMCount = 0; // reset pwm counter |
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| 1805 | - | 76 | } |
| 2041 | - | 77 | |
| 1805 | - | 78 | if (!PWMTimeout) { |
| 1887 | - | 79 | if (checkDelay(beepDelay)) { |
| 80 | if (!beepTime) |
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| 2044 | - | 81 | beep(50); // make noise with 10Hz to signal the compass problem |
| 1887 | - | 82 | beepDelay = setDelay(100); |
| 1801 | - | 83 | } |
| 1612 | dongfang | 84 | } |
| 85 | } |
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| 86 |