/****************************************************************************
*
* Copyright (C) 2013 PX4 Development Team. All rights reserved.
* Author: Julian Oes <joes@student.ethz.ch>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name PX4 nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/**
* @file pwm_limit.c
*
* Lib to limit PWM output
*
* @author Julian Oes <joes@student.ethz.ch>
*/
#include "pwm_limit.h"
#include <math.h>
#include <stdbool.h>
#include <drivers/drv_hrt.h>
__EXPORT void pwm_limit_init(pwm_limit_t *limit)
{
limit->nchannels = 0;
limit->state = LIMIT_STATE_OFF;
limit->time_armed = 0;
return;
}
__EXPORT void pwm_limit_calc(const bool armed, const uint16_t *disarmed_pwm, const uint16_t *min_pwm, const uint16_t *max_pwm, const float *output_requested, uint16_t *effective_pwm, pwm_limit_t *limit)
{
/* first evaluate state changes */
switch (limit->state) {
case LIMIT_STATE_OFF:
if (armed)
limit->state = LIMIT_STATE_RAMP;
limit->time_armed = hrt_absolute_time();
break;
case LIMIT_STATE_INIT:
if (!armed)
limit->state = LIMIT_STATE_OFF;
else if (hrt_absolute_time() - limit->time_armed >= INIT_TIME_US)
limit->state = LIMIT_STATE_RAMP;
break;
case LIMIT_STATE_RAMP:
if (!armed)
limit->state = LIMIT_STATE_OFF;
else if (hrt_absolute_time() - limit->time_armed >= INIT_TIME_US + RAMP_TIME_US)
limit->state = LIMIT_STATE_ON;
break;
case LIMIT_STATE_ON:
if (!armed)
limit->state = LIMIT_STATE_OFF;
break;
default:
break;
}
unsigned progress;
uint16_t temp_pwm;
/* then set effective_pwm based on state */
switch (limit->state) {
case LIMIT_STATE_OFF:
case LIMIT_STATE_INIT:
for (unsigned i=0; i<limit->nchannels; i++) {
effective_pwm[i] = disarmed_pwm[i];
}
break;
case LIMIT_STATE_RAMP:
progress = (hrt_absolute_time() - INIT_TIME_US - limit->time_armed)*10000 / RAMP_TIME_US;
for (unsigned i=0; i<limit->nchannels; i++) {
temp_pwm = output_requested[i] * (max_pwm[i] - min_pwm[i])/2 + (max_pwm[i] + min_pwm[i])/2;
/* already follow user/controller input if higher than min_pwm */
effective_pwm[i] = (disarmed_pwm[i]*(10000-progress) + (temp_pwm > min_pwm[i] ? temp_pwm : min_pwm[i])*progress)/10000;
}
break;
case LIMIT_STATE_ON:
for (unsigned i=0; i<limit->nchannels; i++) {
effective_pwm[i] = output_requested[i] * (max_pwm[i] - min_pwm[i])/2 + (max_pwm[i] + min_pwm[i])/2;
}
break;
default:
break;
}
return;
}
