scoutos / scout_avr / src / range.cpp @ 812788aa
History | View | Annotate | Download (1.86 KB)
| 1 | 1c3c96ce | Tom Mullins | #include "range.h" |
|---|---|---|---|
| 2 | |||
| 3 | extern "C" |
||
| 4 | {
|
||
| 5 | #include <avr/io.h> |
||
| 6 | #include <avr/interrupt.h> |
||
| 7 | } |
||
| 8 | |||
| 9 | /* Ultrasonic Sensor:
|
||
| 10 | * -if RX pin is left open, it will continuously take readings
|
||
| 11 | * -PW output is 147us/in.
|
||
| 12 | * -PW will be high for a maximum of 37.5ms if no target is detected
|
||
| 13 | *
|
||
| 14 | * 37.5ms * 8 MHz / 8 prescaler = 37500 max wait
|
||
| 15 | */
|
||
| 16 | |||
| 17 | 807483bf | Tom Mullins | // so that we can test on a 328 or the stk600
|
| 18 | #if defined(__AVR_ATmega128RFA1__) || defined(__AVR_ATmega2560__)
|
||
| 19 | 1c3c96ce | Tom Mullins | # define read_INT0 (PIND & _BV(PD0))
|
| 20 | ec9e417d | Tom Mullins | # define read_INT1 (PIND & _BV(PD1))
|
| 21 | 1c3c96ce | Tom Mullins | #elif defined(__AVR_ATmega328P__) || defined(__AVR_ATmega328__)
|
| 22 | # define read_INT0 (PIND & _BV(PD2))
|
||
| 23 | ec9e417d | Tom Mullins | # define read_INT1 (PIND & _BV(PD3))
|
| 24 | 1c3c96ce | Tom Mullins | #else
|
| 25 | ec9e417d | Tom Mullins | # error "Please define read_INTx for this device" |
| 26 | 1c3c96ce | Tom Mullins | #endif
|
| 27 | |||
| 28 | ec9e417d | Tom Mullins | struct range_t {
|
| 29 | unsigned int start; // timer value on rising edge |
||
| 30 | unsigned int value; // last measured range |
||
| 31 | } range[2];
|
||
| 32 | |||
| 33 | static void on_edge(int which) |
||
| 34 | 1c3c96ce | Tom Mullins | {
|
| 35 | 807483bf | Tom Mullins | unsigned char int_high; |
| 36 | 812788aa | Tom Mullins | // TODO centralize timer 5
|
| 37 | 31f4a032 | Tom Mullins | // TODO ensure this is in microseconds even for 16MHz
|
| 38 | 812788aa | Tom Mullins | unsigned int time = TCNT5; |
| 39 | 807483bf | Tom Mullins | |
| 40 | if (which)
|
||
| 41 | {
|
||
| 42 | int_high = read_INT1; |
||
| 43 | } |
||
| 44 | else
|
||
| 45 | {
|
||
| 46 | int_high = read_INT0; |
||
| 47 | } |
||
| 48 | |||
| 49 | if (int_high)
|
||
| 50 | 1c3c96ce | Tom Mullins | {
|
| 51 | ec9e417d | Tom Mullins | range[which].start = time; |
| 52 | 1c3c96ce | Tom Mullins | } |
| 53 | else
|
||
| 54 | {
|
||
| 55 | ec9e417d | Tom Mullins | // if timer overflowed since start, this arithmetic should still work out
|
| 56 | range[which].value = time - range[which].start; |
||
| 57 | 1c3c96ce | Tom Mullins | } |
| 58 | } |
||
| 59 | |||
| 60 | ec9e417d | Tom Mullins | ISR(INT0_vect) |
| 61 | {
|
||
| 62 | on_edge(0);
|
||
| 63 | } |
||
| 64 | |||
| 65 | ISR(INT1_vect) |
||
| 66 | {
|
||
| 67 | on_edge(1);
|
||
| 68 | } |
||
| 69 | |||
| 70 | 1c3c96ce | Tom Mullins | void range_init()
|
| 71 | {
|
||
| 72 | ec9e417d | Tom Mullins | // ISCx = 1, edge triggered
|
| 73 | EICRA |= _BV(ISC10) | _BV(ISC00); |
||
| 74 | // enable INT0 and INT1
|
||
| 75 | EIMSK |= _BV(INT1) | _BV(INT0); |
||
| 76 | 1c3c96ce | Tom Mullins | |
| 77 | // CS1 = 2, 1/8 prescaler
|
||
| 78 | f115416e | Tom Mullins | // if this is changed, remember to change recv_edge in bom.cpp!
|
| 79 | 812788aa | Tom Mullins | TCCR5B = _BV(CS51); |
| 80 | 1c3c96ce | Tom Mullins | |
| 81 | 230b1b7f | Tom Mullins | range[0].value = RANGE_ERR;
|
| 82 | range[1].value = RANGE_ERR;
|
||
| 83 | 1c3c96ce | Tom Mullins | } |
| 84 | |||
| 85 | ec9e417d | Tom Mullins | unsigned int range_get(int which) |
| 86 | 1c3c96ce | Tom Mullins | {
|
| 87 | ec9e417d | Tom Mullins | unsigned int ret; |
| 88 | if (0 <= which && which <= 1) |
||
| 89 | {
|
||
| 90 | cli(); |
||
| 91 | ret = range[which].value; |
||
| 92 | sei(); |
||
| 93 | return ret;
|
||
| 94 | } |
||
| 95 | 230b1b7f | Tom Mullins | else return RANGE_ERR; |
| 96 | 1c3c96ce | Tom Mullins | } |