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https://github.com/PX4/PX4-Autopilot.git
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systemlib delete unused ppm_decode
This commit is contained in:
Daniel Agar
committed by
Lorenz Meier
Lorenz Meier
parent
d0bde9ab2a
commit
fda25e9f3a
@@ -1,255 +0,0 @@
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/****************************************************************************
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*
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* Copyright (C) 2012 PX4 Development Team. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name PX4 nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/**
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* @file ppm_decode.c
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*
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* PPM input decoder.
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*/
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#include <px4_config.h>
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#include <stdint.h>
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#include <string.h>
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#include <drivers/drv_hrt.h>
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#include "ppm_decode.h"
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/*
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* PPM decoder tuning parameters.
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*
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* The PPM decoder works as follows.
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*
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* Initially, the decoder waits in the UNSYNCH state for two edges
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* separated by PPM_MIN_START. Once the second edge is detected,
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* the decoder moves to the ARM state.
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*
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* The ARM state expects an edge within PPM_MAX_PULSE_WIDTH, being the
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* timing mark for the first channel. If this is detected, it moves to
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* the INACTIVE state.
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*
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* The INACTIVE phase waits for and discards the next edge, as it is not
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* significant. Once the edge is detected, it moves to the ACTIVE stae.
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*
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* The ACTIVE state expects an edge within PPM_MAX_PULSE_WIDTH, and when
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* received calculates the time from the previous mark and records
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* this time as the value for the next channel.
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*
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* If at any time waiting for an edge, the delay from the previous edge
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* exceeds PPM_MIN_START the frame is deemed to have ended and the recorded
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* values are advertised to clients.
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*/
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#define PPM_MAX_PULSE_WIDTH 500 /* maximum width of a pulse */
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#define PPM_MIN_CHANNEL_VALUE 800 /* shortest valid channel signal */
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#define PPM_MAX_CHANNEL_VALUE 2200 /* longest valid channel signal */
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#define PPM_MIN_START 2500 /* shortest valid start gap */
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/* Input timeout - after this interval we assume signal is lost */
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#define PPM_INPUT_TIMEOUT 100 * 1000 /* 100ms */
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/* Number of same-sized frames required to 'lock' */
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#define PPM_CHANNEL_LOCK 3 /* should be less than the input timeout */
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/* decoded PPM buffer */
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#define PPM_MIN_CHANNELS 4
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#define PPM_MAX_CHANNELS 12
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/*
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* Public decoder state
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*/
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uint16_t ppm_buffer[PPM_MAX_CHANNELS];
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unsigned ppm_decoded_channels;
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hrt_abstime ppm_last_valid_decode;
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static uint16_t ppm_temp_buffer[PPM_MAX_CHANNELS];
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/* PPM decoder state machine */
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static struct {
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uint16_t last_edge; /* last capture time */
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uint16_t last_mark; /* last significant edge */
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unsigned next_channel;
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unsigned count_max;
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enum {
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UNSYNCH = 0,
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ARM,
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ACTIVE,
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INACTIVE
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} phase;
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} ppm;
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void
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ppm_input_init(unsigned count_max)
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{
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ppm_decoded_channels = 0;
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ppm_last_valid_decode = 0;
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memset(&ppm, 0, sizeof(ppm));
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ppm.count_max = count_max;
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}
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void
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ppm_input_decode(bool reset, unsigned count)
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{
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uint16_t width;
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uint16_t interval;
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unsigned i;
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/* if we missed an edge, we have to give up */
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if (reset) {
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goto error;
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}
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/* how long since the last edge? */
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width = count - ppm.last_edge;
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if (count < ppm.last_edge) {
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width += ppm.count_max; /* handle wrapped count */
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}
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ppm.last_edge = count;
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/*
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* If this looks like a start pulse, then push the last set of values
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* and reset the state machine.
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*
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* Note that this is not a "high performance" design; it implies a whole
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* frame of latency between the pulses being received and their being
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* considered valid.
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*/
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if (width >= PPM_MIN_START) {
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/*
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* If the number of channels changes unexpectedly, we don't want
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* to just immediately jump on the new count as it may be a result
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* of noise or dropped edges. Instead, take a few frames to settle.
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*/
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if (ppm.next_channel != ppm_decoded_channels) {
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static unsigned new_channel_count;
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static unsigned new_channel_holdoff;
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if (new_channel_count != ppm.next_channel) {
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/* start the lock counter for the new channel count */
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new_channel_count = ppm.next_channel;
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new_channel_holdoff = PPM_CHANNEL_LOCK;
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} else if (new_channel_holdoff > 0) {
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/* this frame matched the last one, decrement the lock counter */
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new_channel_holdoff--;
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} else {
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/* we have seen PPM_CHANNEL_LOCK frames with the new count, accept it */
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ppm_decoded_channels = new_channel_count;
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new_channel_count = 0;
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}
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} else {
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/* frame channel count matches expected, let's use it */
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if (ppm.next_channel > PPM_MIN_CHANNELS) {
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for (i = 0; i < ppm.next_channel; i++) {
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ppm_buffer[i] = ppm_temp_buffer[i];
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}
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ppm_last_valid_decode = hrt_absolute_time();
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}
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}
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/* reset for the next frame */
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ppm.next_channel = 0;
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/* next edge is the reference for the first channel */
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ppm.phase = ARM;
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return;
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}
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switch (ppm.phase) {
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case UNSYNCH:
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/* we are waiting for a start pulse - nothing useful to do here */
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return;
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case ARM:
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/* we expect a pulse giving us the first mark */
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if (width > PPM_MAX_PULSE_WIDTH) {
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goto error; /* pulse was too long */
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}
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/* record the mark timing, expect an inactive edge */
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ppm.last_mark = count;
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ppm.phase = INACTIVE;
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return;
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case INACTIVE:
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/* this edge is not interesting, but now we are ready for the next mark */
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ppm.phase = ACTIVE;
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/* note that we don't bother looking at the timing of this edge */
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return;
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case ACTIVE:
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/* we expect a well-formed pulse */
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if (width > PPM_MAX_PULSE_WIDTH) {
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goto error; /* pulse was too long */
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}
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/* determine the interval from the last mark */
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interval = count - ppm.last_mark;
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ppm.last_mark = count;
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/* if the mark-mark timing is out of bounds, abandon the frame */
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if ((interval < PPM_MIN_CHANNEL_VALUE) || (interval > PPM_MAX_CHANNEL_VALUE)) {
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goto error;
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}
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/* if we have room to store the value, do so */
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if (ppm.next_channel < PPM_MAX_CHANNELS) {
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ppm_temp_buffer[ppm.next_channel++] = interval;
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}
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ppm.phase = INACTIVE;
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return;
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}
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/* the state machine is corrupted; reset it */
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error:
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/* we don't like the state of the decoder, reset it and try again */
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ppm.phase = UNSYNCH;
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ppm_decoded_channels = 0;
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}
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@@ -61,26 +61,4 @@ __EXPORT extern uint16_t ppm_frame_length; /**< length of the decoded PPM fra
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__EXPORT extern unsigned ppm_decoded_channels; /**< count of decoded channels */
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__EXPORT extern hrt_abstime ppm_last_valid_decode; /**< timestamp of the last valid decode */
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/**
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* Initialise the PPM input decoder.
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*
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* @param count_max The maximum value of the counter passed to
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* ppm_input_decode, used to determine how to
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* handle counter wrap.
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*/
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__EXPORT void ppm_input_init(unsigned count_max);
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/**
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* Inform the decoder of an edge on the PPM input.
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*
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* This function can be registered with the HRT as the PPM edge handler.
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*
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* @param reset If set, the edge detector has missed one or
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* more edges and the decoder needs to be reset.
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* @param count A microsecond timestamp corresponding to the
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* edge, in the range 0-count_max. This value
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* is expected to wrap.
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*/
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__EXPORT void ppm_input_decode(bool reset, unsigned count);
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__END_DECLS
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