ardupilot/libraries/AP_RCProtocol/AP_RCProtocol_PPMSum.cpp

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/*
* This file 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 file 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/>.
*
* Code by Andrew Tridgell and Siddharth Bharat Purohit
*/
#include "AP_RCProtocol_PPMSum.h"
/*
process a PPM-sum pulse of the given width
*/
void AP_RCProtocol_PPMSum::process_pulse(uint32_t width_s0, uint32_t width_s1)
{
if (width_s0 == 0 || width_s1 == 0) {
//invalid data: reset frame
ppm_state._channel_counter = -1;
return;
}
uint32_t width_usec = width_s0 + width_s1;
if (width_usec >= 2700) {
// a long pulse indicates the end of a frame. Reset the
// channel counter so next pulse is channel 0
if (ppm_state._channel_counter >= MIN_RCIN_CHANNELS) {
add_input(ppm_state._channel_counter, ppm_state._pulse_capt, false);
}
ppm_state._channel_counter = 0;
return;
}
if (ppm_state._channel_counter == -1) {
// we are not synchronised
return;
}
/*
we limit inputs to between 700usec and 2300usec. This allows us
to decode SBUS on the same pin, as SBUS will have a maximum
pulse width of 100usec
*/
if (width_usec > 700 && width_usec < 2300) {
// take a reading for the current channel
// buffer these
ppm_state._pulse_capt[ppm_state._channel_counter] = width_usec;
// move to next channel
ppm_state._channel_counter++;
}
// if we have reached the maximum supported channels then
// mark as unsynchronised, so we wait for a wide pulse
if (ppm_state._channel_counter >= MAX_RCIN_CHANNELS) {
add_input(ppm_state._channel_counter, ppm_state._pulse_capt, false);
ppm_state._channel_counter = -1;
}
}