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diff --git a/src/modules/systemlib/ppm_decode.h b/src/modules/systemlib/ppm_decode.h
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+++ b/src/modules/systemlib/ppm_decode.h
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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 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
+\ No newline at end of file