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// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
/*
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "AP_RangeFinder_PulsedLightLRF.h"
#include <AP_HAL/AP_HAL.h>
extern const AP_HAL::HAL& hal;
/*
The constructor also initialises the rangefinder. Note that this
constructor is not called until detect() returns true, so we
already know that we should setup the rangefinder
*/
AP_RangeFinder_PulsedLightLRF::AP_RangeFinder_PulsedLightLRF(RangeFinder &_ranger, uint8_t instance, RangeFinder::RangeFinder_State &_state) :
AP_RangeFinder_Backend(_ranger, instance, _state)
{
}
/*
detect if a PulsedLight rangefinder is connected. We'll detect by
trying to take a reading on I2C. If we get a result the sensor is
there.
*/
bool AP_RangeFinder_PulsedLightLRF::detect(RangeFinder &_ranger, uint8_t instance)
{
if (!start_reading()) {
return false;
}
// give time for the sensor to process the request
hal.scheduler->delay(50);
uint16_t reading_cm;
return get_reading(reading_cm);
}
// start_reading() - ask sensor to make a range reading
bool AP_RangeFinder_PulsedLightLRF::start_reading()
{
// get pointer to i2c bus semaphore
AP_HAL::Semaphore* i2c_sem = hal.i2c->get_semaphore();
// exit immediately if we can't take the semaphore
if (i2c_sem == NULL || !i2c_sem->take(1)) {
return false;
}
// send command to take reading
if (hal.i2c->writeRegister(AP_RANGEFINDER_PULSEDLIGHTLRF_ADDR,
AP_RANGEFINDER_PULSEDLIGHTLRF_MEASURE_REG,
AP_RANGEFINDER_PULSEDLIGHTLRF_MSRREG_ACQUIRE) != 0) {
i2c_sem->give();
return false;
}
// return semaphore
i2c_sem->give();
return true;
}
// read - return last value measured by sensor
bool AP_RangeFinder_PulsedLightLRF::get_reading(uint16_t &reading_cm)
{
uint8_t buff[2];
// get pointer to i2c bus semaphore
AP_HAL::Semaphore* i2c_sem = hal.i2c->get_semaphore();
// exit immediately if we can't take the semaphore
if (i2c_sem == NULL || !i2c_sem->take(1)) {
return false;
}
// read the high and low byte distance registers
if (hal.i2c->readRegisters(AP_RANGEFINDER_PULSEDLIGHTLRF_ADDR,
AP_RANGEFINDER_PULSEDLIGHTLRF_DISTHIGH_REG, 2, &buff[0]) != 0) {
i2c_sem->give();
return false;
}
// combine results into distance
reading_cm = ((uint16_t)buff[0]) << 8 | buff[1];
// return semaphore
i2c_sem->give();
// kick off another reading for next time
// To-Do: replace this with continuous mode
hal.scheduler->delay_microseconds(200);
start_reading();
return true;
}
/*
update the state of the sensor
*/
void AP_RangeFinder_PulsedLightLRF::update(void)
{
if (get_reading(state.distance_cm)) {
// update range_valid state based on distance measured
update_status();
} else {
set_status(RangeFinder::RangeFinder_NoData);
}
}
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