porklib: Simple library for programming Arduino in C
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avr-lib/lib/sonar.c

140 lines
2.6 KiB

#include <avr/io.h>
#include <util/delay.h>
#include <stdint.h>
#include <stdbool.h>
#include "iopins.h"
#include "sonar.h"
// Currently measured sonar
static sonar_t* _so;
// Flag that measurement is in progress
volatile bool sonar_busy;
// Result of last measurement, in millimeters
volatile int16_t sonar_result;
void _sonar_init_do(sonar_t* so, PORT_P port, uint8_t ntx, PORT_P pin, uint8_t nrx)
{
so->port = port;
so->ntx = ntx;
so->pin = pin;
so->nrx = nrx;
switch((const uint16_t) pin) {
case ((const uint16_t) &PINB): so->bank = 0; break;
case ((const uint16_t) &PINC): so->bank = 1; break;
case ((const uint16_t) &PIND): so->bank = 2; break;
}
}
/**
* Start sonar measurement
* Interrupts must be enabled
* TIMER 1 will be used for the async measurement
* Timer 1 overflow and Pin Change interrupts must invoke Sonar handlers.
*/
bool sonar_start(sonar_t* so)
{
if (sonar_busy) return false;
_so = so;
sonar_busy = true;
// make sure the timer is stopped (set clock to NONE)
TCCR1B = 0;
// Timer overflow interrupt enable
// We'll stop measuring on overflow
sbi(TIMSK1, TOIE1);
// Clear the timer value
TCNT1 = 0;
// Set up pin change interrupt mask for the RX pin
switch(so->bank) {
case 0: sbi(PCMSK0, so->nrx); break;
case 1: sbi(PCMSK1, so->nrx); break;
case 2: sbi(PCMSK2, so->nrx); break;
}
// send positive pulse
sbi_p(so->port, so->ntx);
_delay_us(_SNR_TRIG_TIME);
cbi_p(so->port, so->ntx);
// Wait for start of response
while (bit_is_low_p(so->pin, so->nrx));
// Set timer clock source: F_CPU / 8 (0.5 us resolution)
TCCR1B = (0b010 << CS10);
// Enable pin change interrupt
sbi(PCICR, so->bank);
return true;
}
/** Stop the timer */
void _sonar_stop()
{
// stop timer
TCCR1B = 0;
// Disable RX pin interrupt mask
switch(_so->bank) {
case 0: PCMSK0 &= ~(1 << (_so->nrx)); break;
case 1: PCMSK1 &= ~(1 << (_so->nrx)); break;
case 2: PCMSK2 &= ~(1 << (_so->nrx)); break;
}
// Disable timer1 overflow interrupt
cbi(TIMSK1, TOIE1);
sonar_busy = false;
}
/** Handle TIMER1_OVF (returns true if consumed) */
inline bool sonar_handle_t1ovf()
{
if (!sonar_busy) return false; // nothing
sonar_result = -1;
_sonar_stop();
return true;
}
/** Handle pin change interrupt (returns true if consumed) */
inline bool sonar_handle_pci()
{
if (!sonar_busy) {
return false; // nothing
}
if (bit_is_high_p(_so->pin, _so->nrx)) {
// rx is high, not our pin change event
return false;
}
uint64_t x = TCNT1;
x /= _SNR_DIV_CONST;
x *= 100000000L;
x /= F_CPU;
sonar_result = (int16_t) x;
// no obstacle
if (sonar_result > _SNR_MAX_DIST) sonar_result = -1;
_sonar_stop();
return true;
}