root / scout_avr / src / range.cpp @ 807483bf
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| 1 | 1c3c96ce | Tom Mullins | #include "range.h" |
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| 2 | |||
| 3 | extern "C" |
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| 4 | {
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| 5 | #include <avr/io.h> |
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| 6 | #include <avr/interrupt.h> |
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| 7 | } |
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| 8 | |||
| 9 | /* Ultrasonic Sensor:
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| 10 | * -if RX pin is left open, it will continuously take readings
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| 11 | * -PW output is 147us/in.
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| 12 | * -PW will be high for a maximum of 37.5ms if no target is detected
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| 13 | *
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| 14 | * 37.5ms * 8 MHz / 8 prescaler = 37500 max wait
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| 15 | */
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| 16 | |||
| 17 | 807483bf | Tom Mullins | // so that we can test on a 328 or the stk600
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| 18 | #if defined(__AVR_ATmega128RFA1__) || defined(__AVR_ATmega2560__)
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| 19 | 1c3c96ce | Tom Mullins | # define read_INT0 (PIND & _BV(PD0))
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| 20 | ec9e417d | Tom Mullins | # define read_INT1 (PIND & _BV(PD1))
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| 21 | 1c3c96ce | Tom Mullins | #elif defined(__AVR_ATmega328P__) || defined(__AVR_ATmega328__)
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| 22 | # define read_INT0 (PIND & _BV(PD2))
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| 23 | ec9e417d | Tom Mullins | # define read_INT1 (PIND & _BV(PD3))
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| 24 | 1c3c96ce | Tom Mullins | #else
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| 25 | ec9e417d | Tom Mullins | # error "Please define read_INTx for this device" |
| 26 | 1c3c96ce | Tom Mullins | #endif
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| 27 | |||
| 28 | ec9e417d | Tom Mullins | struct range_t {
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| 29 | unsigned int start; // timer value on rising edge |
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| 30 | unsigned int value; // last measured range |
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| 31 | } range[2];
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| 32 | |||
| 33 | static void on_edge(int which) |
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| 34 | 1c3c96ce | Tom Mullins | {
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| 35 | 807483bf | Tom Mullins | unsigned char int_high; |
| 36 | ec9e417d | Tom Mullins | unsigned int time = TCNT1; |
| 37 | 807483bf | Tom Mullins | |
| 38 | if (which)
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| 39 | {
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| 40 | int_high = read_INT1; |
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| 41 | } |
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| 42 | else
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| 43 | {
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| 44 | int_high = read_INT0; |
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| 45 | } |
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| 46 | |||
| 47 | if (int_high)
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| 48 | 1c3c96ce | Tom Mullins | {
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| 49 | ec9e417d | Tom Mullins | range[which].start = time; |
| 50 | 1c3c96ce | Tom Mullins | } |
| 51 | else
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| 52 | {
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| 53 | ec9e417d | Tom Mullins | // if timer overflowed since start, this arithmetic should still work out
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| 54 | range[which].value = time - range[which].start; |
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| 55 | 1c3c96ce | Tom Mullins | } |
| 56 | } |
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| 57 | |||
| 58 | ec9e417d | Tom Mullins | ISR(INT0_vect) |
| 59 | {
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| 60 | on_edge(0);
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| 61 | } |
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| 62 | |||
| 63 | ISR(INT1_vect) |
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| 64 | {
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| 65 | on_edge(1);
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| 66 | } |
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| 67 | |||
| 68 | 1c3c96ce | Tom Mullins | void range_init()
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| 69 | {
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| 70 | ec9e417d | Tom Mullins | // ISCx = 1, edge triggered
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| 71 | EICRA |= _BV(ISC10) | _BV(ISC00); |
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| 72 | // enable INT0 and INT1
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| 73 | EIMSK |= _BV(INT1) | _BV(INT0); |
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| 74 | 1c3c96ce | Tom Mullins | |
| 75 | // CS1 = 2, 1/8 prescaler
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| 76 | TCCR1B = _BV(CS11); |
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| 77 | |||
| 78 | 230b1b7f | Tom Mullins | range[0].value = RANGE_ERR;
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| 79 | range[1].value = RANGE_ERR;
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| 80 | 1c3c96ce | Tom Mullins | } |
| 81 | |||
| 82 | ec9e417d | Tom Mullins | unsigned int range_get(int which) |
| 83 | 1c3c96ce | Tom Mullins | {
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| 84 | ec9e417d | Tom Mullins | unsigned int ret; |
| 85 | if (0 <= which && which <= 1) |
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| 86 | {
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| 87 | cli(); |
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| 88 | ret = range[which].value; |
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| 89 | sei(); |
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| 90 | return ret;
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| 91 | } |
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| 92 | 230b1b7f | Tom Mullins | else return RANGE_ERR; |
| 93 | 1c3c96ce | Tom Mullins | } |