root / scout_avr / src / range.cpp @ 47e26dee
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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 | 399f7d1b | Tom Mullins | * 37.5ms * 16 MHz / 64 prescaler = 9375 max wait
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| 16 | 1c3c96ce | Tom Mullins | */
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| 17 | |||
| 18 | ec9e417d | Tom Mullins | struct range_t {
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| 19 | unsigned int start; // timer value on rising edge |
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| 20 | unsigned int value; // last measured range |
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| 21 | fd73d758 | Tom Mullins | char done;
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| 22 | } volatile range[2]; |
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| 23 | ec9e417d | Tom Mullins | |
| 24 | static void on_edge(int which) |
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| 25 | 1c3c96ce | Tom Mullins | {
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| 26 | 807483bf | Tom Mullins | unsigned char int_high; |
| 27 | 812788aa | Tom Mullins | unsigned int time = TCNT5; |
| 28 | 807483bf | Tom Mullins | |
| 29 | if (which)
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| 30 | {
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| 31 | cc9ca04e | Tom Mullins | int_high = PIN_SONAR_PWM & _BV(P_SONAR_PWM1); |
| 32 | 807483bf | Tom Mullins | } |
| 33 | else
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| 34 | {
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| 35 | cc9ca04e | Tom Mullins | int_high = PIN_SONAR_PWM & _BV(P_SONAR_PWM0); |
| 36 | 807483bf | Tom Mullins | } |
| 37 | |||
| 38 | if (int_high)
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| 39 | 1c3c96ce | Tom Mullins | {
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| 40 | ec9e417d | Tom Mullins | range[which].start = time; |
| 41 | 1c3c96ce | Tom Mullins | } |
| 42 | else
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| 43 | {
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| 44 | fd73d758 | Tom Mullins | PORT_SONAR_TX &= ~ _BV(P_SONAR_TX); |
| 45 | ec9e417d | Tom Mullins | // if timer overflowed since start, this arithmetic should still work out
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| 46 | range[which].value = time - range[which].start; |
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| 47 | fd73d758 | Tom Mullins | range[which].done = 1;
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| 48 | 1c3c96ce | Tom Mullins | } |
| 49 | } |
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| 50 | |||
| 51 | cc9ca04e | Tom Mullins | ISR(INT3_vect) |
| 52 | ec9e417d | Tom Mullins | {
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| 53 | on_edge(0);
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| 54 | } |
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| 55 | |||
| 56 | cc9ca04e | Tom Mullins | ISR(INT2_vect) |
| 57 | ec9e417d | Tom Mullins | {
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| 58 | on_edge(1);
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| 59 | } |
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| 60 | |||
| 61 | 1c3c96ce | Tom Mullins | void range_init()
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| 62 | {
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| 63 | ec9e417d | Tom Mullins | // ISCx = 1, edge triggered
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| 64 | cc9ca04e | Tom Mullins | EICRA |= _BV(ISC20) | _BV(ISC30); |
| 65 | // enable INT2 and INT3
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| 66 | EIMSK |= _BV(INT2) | _BV(INT3); |
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| 67 | 1c3c96ce | Tom Mullins | |
| 68 | 399f7d1b | Tom Mullins | // CS1 = 3, 1/64 prescaler
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| 69 | f115416e | Tom Mullins | // if this is changed, remember to change recv_edge in bom.cpp!
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| 70 | 399f7d1b | Tom Mullins | TCCR5B = _BV(CS50) | _BV(CS51); |
| 71 | fd73d758 | Tom Mullins | |
| 72 | // set tx as output
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| 73 | DDRG |= _BV(DDG1); |
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| 74 | PORT_SONAR_TX &= ~ _BV(P_SONAR_TX); |
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| 75 | 1c3c96ce | Tom Mullins | } |
| 76 | |||
| 77 | fd73d758 | Tom Mullins | void range_measure(unsigned int *values) |
| 78 | 1c3c96ce | Tom Mullins | {
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| 79 | fd73d758 | Tom Mullins | int i;
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| 80 | |||
| 81 | for (i = 0; i < 2; i++) |
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| 82 | {
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| 83 | range[i].value = RANGE_ERR; |
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| 84 | range[i].done = 0;
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| 85 | } |
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| 86 | |||
| 87 | // TODO ensure that one interrupt won't be delayed because of the other
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| 88 | PORT_SONAR_TX |= _BV(P_SONAR_TX); |
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| 89 | |||
| 90 | for (i = 0; i < 2; i++) |
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| 91 | ec9e417d | Tom Mullins | {
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| 92 | fd73d758 | Tom Mullins | while (!range[i].done) {}
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| 93 | values[i] = range[i].value; |
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| 94 | ec9e417d | Tom Mullins | } |
| 95 | 1c3c96ce | Tom Mullins | } |