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/****************************************************************************
*
* Copyright (C) 2012 PX4 Development Team. All rights reserved.
*
* 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 ppm_decode.h
*
* PPM input decoder.
*/
#pragma once
#include <drivers/drv_hrt.h>
/**
* Maximum number of channels that we will decode.
*/
#define PPM_MAX_CHANNELS 12
/* PPM input nominal min/max values */
#define PPM_MIN 1000
#define PPM_MAX 2000
#define PPM_MID ((PPM_MIN + PPM_MAX) / 2)
__BEGIN_DECLS
/*
* PPM decoder state
*/
__EXPORT extern uint16_t ppm_buffer[PPM_MAX_CHANNELS]; /**< decoded PPM channel values */
__EXPORT extern uint16_t ppm_frame_length; /**< length of the decoded PPM frame (includes gap) */
__EXPORT extern unsigned ppm_decoded_channels; /**< count of decoded channels */
__EXPORT extern hrt_abstime ppm_last_valid_decode; /**< timestamp of the last valid decode */
/**
* Initialise the PPM input decoder.
*
* @param count_max The maximum value of the counter passed to
* ppm_input_decode, used to determine how to
* handle counter wrap.
*/
__EXPORT void ppm_input_init(unsigned count_max);
/**
* Inform the decoder of an edge on the PPM input.
*
* This function can be registered with the HRT as the PPM edge handler.
*
* @param reset If set, the edge detector has missed one or
* more edges and the decoder needs to be reset.
* @param count A microsecond timestamp corresponding to the
* edge, in the range 0-count_max. This value
* is expected to wrap.
*/
__EXPORT void ppm_input_decode(bool reset, unsigned count);
__END_DECLS
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