diff options
Diffstat (limited to 'sys/dist.c')
| -rw-r--r-- | sys/dist.c | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/sys/dist.c b/sys/dist.c new file mode 100644 index 0000000..e656fc2 --- /dev/null +++ b/sys/dist.c @@ -0,0 +1,50 @@ +#include "dist.h" +#include "irq.h" +#include "clock.h" + +#define F_CPU_KHZ (F_CPU/1000) +#define LOOPS (2000 * F_CPU_KHZ) + +//speed of sound in cm/s +#define C_SOUND (340l*100) + +#include <avr/io.h> +static void pin_change(void* sensor) +{ + struct dist_sensor* sens = (struct dist_sensor*) sensor; + if (pin_read(sens->echo_pin)) { //rising edge + sens->delta_time = time_micros(); + } else { //falling edge + sens->delta_time = time_micros() - sens->delta_time; + uint32_t cm = C_SOUND * sens->delta_time / 1000000; + sens->distance = (uint16_t) cm; + + DDRB |= (1 << PB1); + PORTB |= (1 << PB1); + dist_read(sensor); + } +} + +void dist_init(struct dist_sensor* sens) +{ + pin_mode(sens->echo_pin, INPUT); + pin_mode(sens->trig_pin, OUTPUT); + pin_write(sens->trig_pin, false); + irq_register(sens->echo_irq, pin_change, sens); + + sens->distance = 0; + sens->delta_time = 0; +} + +/* + Initiate read by pulsing trigger pin for 5us. + Bringing the line down for 2us assures a clean pulse. +*/ +void dist_read(struct dist_sensor* sens) +{ + pin_write(sens->trig_pin, false); + wait_micros(2); + pin_write(sens->trig_pin, true); + wait_micros(5); + pin_write(sens->trig_pin, false); +} |