scoutos / scout_avr / src / range.cpp @ cc9ca04e
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| 1 | 1c3c96ce | Tom Mullins | extern "C" |
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| 2 | {
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| 3 | #include <avr/io.h> |
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| 4 | #include <avr/interrupt.h> |
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| 5 | } |
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| 6 | cc9ca04e | Tom Mullins | #include "range.h" |
| 7 | 1c3c96ce | Tom Mullins | |
| 8 | /* Ultrasonic Sensor:
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| 9 | * -if RX pin is left open, it will continuously take readings
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| 10 | * -PW output is 147us/in.
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| 11 | * -PW will be high for a maximum of 37.5ms if no target is detected
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| 12 | *
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| 13 | * 37.5ms * 8 MHz / 8 prescaler = 37500 max wait
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| 14 | cc9ca04e | Tom Mullins | * 37.5ms * 16 MHz / 8 prescaler = problem
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| 15 | 1c3c96ce | Tom Mullins | */
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| 16 | |||
| 17 | ec9e417d | Tom Mullins | struct range_t {
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| 18 | unsigned int start; // timer value on rising edge |
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| 19 | unsigned int value; // last measured range |
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| 20 | } range[2];
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| 21 | |||
| 22 | static void on_edge(int which) |
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| 23 | 1c3c96ce | Tom Mullins | {
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| 24 | 807483bf | Tom Mullins | unsigned char int_high; |
| 25 | 812788aa | Tom Mullins | unsigned int time = TCNT5; |
| 26 | 807483bf | Tom Mullins | |
| 27 | if (which)
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| 28 | {
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| 29 | cc9ca04e | Tom Mullins | int_high = PIN_SONAR_PWM & _BV(P_SONAR_PWM1); |
| 30 | 807483bf | Tom Mullins | } |
| 31 | else
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| 32 | {
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| 33 | cc9ca04e | Tom Mullins | int_high = PIN_SONAR_PWM & _BV(P_SONAR_PWM0); |
| 34 | 807483bf | Tom Mullins | } |
| 35 | |||
| 36 | if (int_high)
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| 37 | 1c3c96ce | Tom Mullins | {
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| 38 | ec9e417d | Tom Mullins | range[which].start = time; |
| 39 | 1c3c96ce | Tom Mullins | } |
| 40 | else
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| 41 | {
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| 42 | ec9e417d | Tom Mullins | // if timer overflowed since start, this arithmetic should still work out
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| 43 | range[which].value = time - range[which].start; |
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| 44 | 1c3c96ce | Tom Mullins | } |
| 45 | } |
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| 46 | |||
| 47 | cc9ca04e | Tom Mullins | ISR(INT3_vect) |
| 48 | ec9e417d | Tom Mullins | {
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| 49 | on_edge(0);
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| 50 | } |
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| 51 | |||
| 52 | cc9ca04e | Tom Mullins | ISR(INT2_vect) |
| 53 | ec9e417d | Tom Mullins | {
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| 54 | on_edge(1);
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| 55 | } |
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| 56 | |||
| 57 | 1c3c96ce | Tom Mullins | void range_init()
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| 58 | {
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| 59 | ec9e417d | Tom Mullins | // ISCx = 1, edge triggered
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| 60 | cc9ca04e | Tom Mullins | EICRA |= _BV(ISC20) | _BV(ISC30); |
| 61 | // enable INT2 and INT3
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| 62 | EIMSK |= _BV(INT2) | _BV(INT3); |
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| 63 | 1c3c96ce | Tom Mullins | |
| 64 | // CS1 = 2, 1/8 prescaler
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| 65 | f115416e | Tom Mullins | // if this is changed, remember to change recv_edge in bom.cpp!
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| 66 | 812788aa | Tom Mullins | TCCR5B = _BV(CS51); |
| 67 | 1c3c96ce | Tom Mullins | |
| 68 | 230b1b7f | Tom Mullins | range[0].value = RANGE_ERR;
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| 69 | range[1].value = RANGE_ERR;
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| 70 | 1c3c96ce | Tom Mullins | } |
| 71 | |||
| 72 | ec9e417d | Tom Mullins | unsigned int range_get(int which) |
| 73 | 1c3c96ce | Tom Mullins | {
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| 74 | ec9e417d | Tom Mullins | unsigned int ret; |
| 75 | if (0 <= which && which <= 1) |
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| 76 | {
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| 77 | cli(); |
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| 78 | ret = range[which].value; |
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| 79 | sei(); |
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| 80 | return ret;
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| 81 | } |
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| 82 | 230b1b7f | Tom Mullins | else return RANGE_ERR; |
| 83 | 1c3c96ce | Tom Mullins | } |