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/****************************************************************************
*
* Copyright (c) 2013, 2014 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>
#include <stdio.h>
void pwm_limit_init(pwm_limit_t *limit)
{
limit->state = PWM_LIMIT_STATE_INIT;
limit->time_armed = 0;
return;
}
void pwm_limit_calc(const bool armed, const unsigned num_channels, const uint16_t *disarmed_pwm, const uint16_t *min_pwm, const uint16_t *max_pwm, const float *output, uint16_t *effective_pwm, pwm_limit_t *limit)
{
/* first evaluate state changes */
switch (limit->state) {
case PWM_LIMIT_STATE_INIT:
if (armed) {
/* set arming time for the first call */
if (limit->time_armed == 0) {
limit->time_armed = hrt_absolute_time();
}
if (hrt_elapsed_time(&limit->time_armed) >= INIT_TIME_US) {
limit->state = PWM_LIMIT_STATE_OFF;
}
}
break;
case PWM_LIMIT_STATE_OFF:
if (armed) {
limit->state = PWM_LIMIT_STATE_RAMP;
/* reset arming time, used for ramp timing */
limit->time_armed = hrt_absolute_time();
}
break;
case PWM_LIMIT_STATE_RAMP:
if (!armed) {
limit->state = PWM_LIMIT_STATE_OFF;
} else if (hrt_elapsed_time(&limit->time_armed) >= RAMP_TIME_US) {
limit->state = PWM_LIMIT_STATE_ON;
}
break;
case PWM_LIMIT_STATE_ON:
if (!armed) {
limit->state = PWM_LIMIT_STATE_OFF;
}
break;
default:
break;
}
unsigned progress;
uint16_t temp_pwm;
/* then set effective_pwm based on state */
switch (limit->state) {
case PWM_LIMIT_STATE_OFF:
case PWM_LIMIT_STATE_INIT:
for (unsigned i=0; i<num_channels; i++) {
effective_pwm[i] = disarmed_pwm[i];
}
break;
case PWM_LIMIT_STATE_RAMP:
{
hrt_abstime diff = hrt_elapsed_time(&limit->time_armed);
progress = diff * 10000 / RAMP_TIME_US;
for (unsigned i=0; i<num_channels; i++) {
uint16_t ramp_min_pwm;
/* if a disarmed pwm value was set, blend between disarmed and min */
if (disarmed_pwm[i] > 0) {
/* safeguard against overflows */
unsigned disarmed = disarmed_pwm[i];
if (disarmed > min_pwm[i]) {
disarmed = min_pwm[i];
}
unsigned disarmed_min_diff = min_pwm[i] - disarmed;
ramp_min_pwm = disarmed + (disarmed_min_diff * progress) / 10000;
} else {
/* no disarmed pwm value set, choose min pwm */
ramp_min_pwm = min_pwm[i];
}
effective_pwm[i] = output[i] * (max_pwm[i] - ramp_min_pwm)/2 + (max_pwm[i] + ramp_min_pwm)/2;
}
}
break;
case PWM_LIMIT_STATE_ON:
for (unsigned i=0; i<num_channels; i++) {
effective_pwm[i] = output[i] * (max_pwm[i] - min_pwm[i])/2 + (max_pwm[i] + min_pwm[i])/2;
}
break;
default:
break;
}
return;
}
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