scoutos / scout_avr / src / range.cpp @ 86b48573
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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 | f1582e6c | Tom Mullins | #include <util/delay.h> |
| 6 | 1c3c96ce | Tom Mullins | } |
| 7 | cc9ca04e | Tom Mullins | #include "range.h" |
| 8 | 1c3c96ce | Tom Mullins | |
| 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 | cc9ca04e | Tom Mullins | * 37.5ms * 16 MHz / 8 prescaler = problem
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| 16 | 399f7d1b | Tom Mullins | * 37.5ms * 16 MHz / 64 prescaler = 9375 max wait
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| 17 | 86b48573 | Tom Mullins | * 147us/in * 16 MHz / 64 prescaler = 1.44685039 ticks / mm
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| 18 | 1c3c96ce | Tom Mullins | */
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| 19 | |||
| 20 | ec9e417d | Tom Mullins | struct range_t {
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| 21 | unsigned int start; // timer value on rising edge |
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| 22 | unsigned int value; // last measured range |
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| 23 | 86b48573 | Tom Mullins | char busy;
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| 24 | fd73d758 | Tom Mullins | } volatile range[2]; |
| 25 | ec9e417d | Tom Mullins | |
| 26 | static void on_edge(int which) |
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| 27 | 1c3c96ce | Tom Mullins | {
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| 28 | 807483bf | Tom Mullins | unsigned char int_high; |
| 29 | 812788aa | Tom Mullins | unsigned int time = TCNT5; |
| 30 | 807483bf | Tom Mullins | |
| 31 | if (which)
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| 32 | {
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| 33 | cc9ca04e | Tom Mullins | int_high = PIN_SONAR_PWM & _BV(P_SONAR_PWM1); |
| 34 | 807483bf | Tom Mullins | } |
| 35 | else
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| 36 | {
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| 37 | cc9ca04e | Tom Mullins | int_high = PIN_SONAR_PWM & _BV(P_SONAR_PWM0); |
| 38 | 807483bf | Tom Mullins | } |
| 39 | |||
| 40 | if (int_high)
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| 41 | 1c3c96ce | Tom Mullins | {
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| 42 | ec9e417d | Tom Mullins | range[which].start = time; |
| 43 | 86b48573 | Tom Mullins | range[which].busy = 1;
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| 44 | 1c3c96ce | Tom Mullins | } |
| 45 | else
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| 46 | {
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| 47 | ec9e417d | Tom Mullins | // if timer overflowed since start, this arithmetic should still work out
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| 48 | range[which].value = time - range[which].start; |
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| 49 | 86b48573 | Tom Mullins | range[which].busy = 0;
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| 50 | 1c3c96ce | Tom Mullins | } |
| 51 | } |
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| 52 | |||
| 53 | cc9ca04e | Tom Mullins | ISR(INT3_vect) |
| 54 | ec9e417d | Tom Mullins | {
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| 55 | on_edge(0);
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| 56 | } |
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| 57 | |||
| 58 | cc9ca04e | Tom Mullins | ISR(INT2_vect) |
| 59 | ec9e417d | Tom Mullins | {
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| 60 | on_edge(1);
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| 61 | } |
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| 62 | |||
| 63 | 1c3c96ce | Tom Mullins | void range_init()
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| 64 | {
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| 65 | ec9e417d | Tom Mullins | // ISCx = 1, edge triggered
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| 66 | cc9ca04e | Tom Mullins | EICRA |= _BV(ISC20) | _BV(ISC30); |
| 67 | // enable INT2 and INT3
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| 68 | EIMSK |= _BV(INT2) | _BV(INT3); |
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| 69 | 1c3c96ce | Tom Mullins | |
| 70 | 399f7d1b | Tom Mullins | // CS1 = 3, 1/64 prescaler
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| 71 | f115416e | Tom Mullins | // if this is changed, remember to change recv_edge in bom.cpp!
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| 72 | 399f7d1b | Tom Mullins | TCCR5B = _BV(CS50) | _BV(CS51); |
| 73 | fd73d758 | Tom Mullins | |
| 74 | // set tx as output
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| 75 | DDRG |= _BV(DDG1); |
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| 76 | PORT_SONAR_TX &= ~ _BV(P_SONAR_TX); |
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| 77 | 1c3c96ce | Tom Mullins | } |
| 78 | |||
| 79 | fd73d758 | Tom Mullins | void range_measure(unsigned int *values) |
| 80 | 1c3c96ce | Tom Mullins | {
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| 81 | fd73d758 | Tom Mullins | int i;
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| 82 | |||
| 83 | for (i = 0; i < 2; i++) |
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| 84 | {
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| 85 | range[i].value = RANGE_ERR; |
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| 86 | 86b48573 | Tom Mullins | range[i].busy = 0;
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| 87 | fd73d758 | Tom Mullins | } |
| 88 | |||
| 89 | // TODO ensure that one interrupt won't be delayed because of the other
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| 90 | PORT_SONAR_TX |= _BV(P_SONAR_TX); |
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| 91 | 86b48573 | Tom Mullins | _delay_ms(40);
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| 92 | f1582e6c | Tom Mullins | PORT_SONAR_TX &= ~ _BV(P_SONAR_TX); |
| 93 | fd73d758 | Tom Mullins | |
| 94 | for (i = 0; i < 2; i++) |
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| 95 | ec9e417d | Tom Mullins | {
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| 96 | 86b48573 | Tom Mullins | while (range[i].busy) {}
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| 97 | values[i] = range[i].value; |
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| 98 | ec9e417d | Tom Mullins | } |
| 99 | 1c3c96ce | Tom Mullins | } |