ardupilot/libraries/AP_RPM/RPM_PX4_PWM.cpp

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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_HAL.h>
#if CONFIG_HAL_BOARD == HAL_BOARD_PX4 || CONFIG_HAL_BOARD == HAL_BOARD_VRBRAIN
#include "RPM_PX4_PWM.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <drivers/drv_pwm_input.h>
#include <drivers/drv_hrt.h>
#include <drivers/drv_sensor.h>
#include <uORB/topics/pwm_input.h>
#include <stdio.h>
#include <errno.h>
#include <math.h>
extern const AP_HAL::HAL& hal;
/*
don't accept periods below 100us as it is probably ringing of the
signal. It would represent 600k RPM
*/
#define RPM_MIN_PERIOD_US 100
/*
open the sensor in constructor
*/
AP_RPM_PX4_PWM::AP_RPM_PX4_PWM(AP_RPM &_ap_rpm, uint8_t instance, AP_RPM::RPM_State &_state) :
AP_RPM_Backend(_ap_rpm, instance, _state)
{
_fd = open(PWMIN0_DEVICE_PATH, O_RDONLY);
if (_fd == -1) {
hal.console->printf("Unable to open %s\n", PWMIN0_DEVICE_PATH);
return;
}
// keep a queue of 5 samples to reduce noise by averaging
if (ioctl(_fd, SENSORIOCSQUEUEDEPTH, 5) != 0) {
hal.console->printf("Failed to setup RPM queue\n");
close(_fd);
_fd = -1;
return;
}
}
/*
close the file descriptor
*/
AP_RPM_PX4_PWM::~AP_RPM_PX4_PWM()
{
if (_fd != -1) {
close(_fd);
_fd = -1;
}
}
void AP_RPM_PX4_PWM::update(void)
{
if (_fd == -1) {
return;
}
struct pwm_input_s pwm;
uint16_t count = 0;
const float scaling = ap_rpm._scaling[state.instance];
float sum = 0;
while (::read(_fd, &pwm, sizeof(pwm)) == sizeof(pwm)) {
// the px4 pwm_input driver reports the period in microseconds
if (pwm.period > RPM_MIN_PERIOD_US) {
sum += (1.0e6f * 60) / pwm.period;
count++;
}
}
if (count != 0) {
state.rate_rpm = scaling * sum / count;
state.last_reading_ms = hal.scheduler->millis();
}
}
#endif // CONFIG_HAL_BOARD