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Diffstat (limited to 'src/modules/systemlib/ppm_decode.h')
-rw-r--r-- | src/modules/systemlib/ppm_decode.h | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/src/modules/systemlib/ppm_decode.h b/src/modules/systemlib/ppm_decode.h new file mode 100644 index 000000000..6c5e15345 --- /dev/null +++ b/src/modules/systemlib/ppm_decode.h @@ -0,0 +1,85 @@ +/**************************************************************************** + * + * 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 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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