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ardupilot/libraries/AP_HAL/utility/sumd.cpp

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/*
SUMD decoder, based on PX4Firmware/src/rc/lib/rc/sumd.c from PX4Firmware
modified for use in AP_HAL_* by Andrew Tridgell
*/
/****************************************************************************
*
* Copyright (c) 2015 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 sumd.h
*
* RC protocol definition for Graupner HoTT transmitter (SUMD/SUMH Protocol)
*
* @author Marco Bauer <marco@wtns.de>
*/
#include <stdio.h>
#include <stdint.h>
#include "sumd.h"
#define SUMD_MAX_CHANNELS 32
#define SUMD_HEADER_LENGTH 3
#define SUMD_HEADER_ID 0xA8
#define SUMD_ID_SUMH 0x00
#define SUMD_ID_SUMD 0x01
#define SUMD_ID_FAILSAFE 0x81
#pragma pack(push, 1)
typedef struct {
uint8_t header; ///< 0xA8 for a valid packet
uint8_t status; ///< 0x01 valid and live SUMD data frame / 0x00 = SUMH / 0x81 = Failsafe
uint8_t length; ///< Channels
uint8_t sumd_data[SUMD_MAX_CHANNELS * 2]; ///< ChannelData (High Byte/ Low Byte)
uint8_t crc16_high; ///< High Byte of 16 Bit CRC
uint8_t crc16_low; ///< Low Byte of 16 Bit CRC
uint8_t telemetry; ///< Telemetry request
uint8_t crc8; ///< SUMH CRC8
} ReceiverFcPacketHoTT;
#pragma pack(pop)
enum SUMD_DECODE_STATE {
SUMD_DECODE_STATE_UNSYNCED = 0,
SUMD_DECODE_STATE_GOT_HEADER,
SUMD_DECODE_STATE_GOT_STATE,
SUMD_DECODE_STATE_GOT_LEN,
SUMD_DECODE_STATE_GOT_DATA,
SUMD_DECODE_STATE_GOT_CRC,
SUMD_DECODE_STATE_GOT_CRC16_BYTE_1,
SUMD_DECODE_STATE_GOT_CRC16_BYTE_2
};
/*
const char *decode_states[] = {"UNSYNCED",
"GOT_HEADER",
"GOT_STATE",
"GOT_LEN",
"GOT_DATA",
"GOT_CRC",
"GOT_CRC16_BYTE_1",
"GOT_CRC16_BYTE_2"
};
*/
static uint8_t _crc8 = 0x00;
static uint16_t _crc16 = 0x0000;
static bool _sumd = true;
static bool _crcOK = false;
static bool _debug = false;
/* define range mapping here, -+100% -> 1000..2000 */
#define SUMD_RANGE_MIN 0.0f
#define SUMD_RANGE_MAX 4096.0f
#define SUMD_TARGET_MIN 1000.0f
#define SUMD_TARGET_MAX 2000.0f
/* pre-calculate the floating point stuff as far as possible at compile time */
#define SUMD_SCALE_FACTOR ((SUMD_TARGET_MAX - SUMD_TARGET_MIN) / (SUMD_RANGE_MAX - SUMD_RANGE_MIN))
#define SUMD_SCALE_OFFSET (int)(SUMD_TARGET_MIN - (SUMD_SCALE_FACTOR * SUMD_RANGE_MIN + 0.5f))
static enum SUMD_DECODE_STATE _decode_state = SUMD_DECODE_STATE_UNSYNCED;
static uint8_t _rxlen;
static ReceiverFcPacketHoTT _rxpacket;
static uint16_t sumd_crc16(uint16_t crc, uint8_t value)
{
int i;
crc ^= (uint16_t)value << 8;
for (i = 0; i < 8; i++) {
crc = (crc & 0x8000) ? (crc << 1) ^ 0x1021 : (crc << 1);
}
return crc;
}
static uint8_t sumd_crc8(uint8_t crc, uint8_t value)
{
crc += value;
return crc;
}
int sumd_decode(uint8_t byte, uint8_t *rssi, uint8_t *rx_count, uint16_t *channel_count, uint16_t *channels,
uint16_t max_chan_count)
{
int ret = 1;
switch (_decode_state) {
case SUMD_DECODE_STATE_UNSYNCED:
if (_debug) {
printf(" SUMD_DECODE_STATE_UNSYNCED \n") ;
}
if (byte == SUMD_HEADER_ID) {
_rxpacket.header = byte;
_sumd = true;
_rxlen = 0;
_crc16 = 0x0000;
_crc8 = 0x00;
_crcOK = false;
_crc16 = sumd_crc16(_crc16, byte);
_crc8 = sumd_crc8(_crc8, byte);
_decode_state = SUMD_DECODE_STATE_GOT_HEADER;
if (_debug) {
printf(" SUMD_DECODE_STATE_GOT_HEADER: %x \n", byte) ;
}
} else {
ret = 3;
}
break;
case SUMD_DECODE_STATE_GOT_HEADER:
if (byte == SUMD_ID_SUMD || byte == SUMD_ID_SUMH) {
_rxpacket.status = byte;
if (byte == SUMD_ID_SUMH) {
_sumd = false;
}
if (_sumd) {
_crc16 = sumd_crc16(_crc16, byte);
} else {
_crc8 = sumd_crc8(_crc8, byte);
}
_decode_state = SUMD_DECODE_STATE_GOT_STATE;
if (_debug) {
printf(" SUMD_DECODE_STATE_GOT_STATE: %x \n", byte) ;
}
} else {
_decode_state = SUMD_DECODE_STATE_UNSYNCED;
}
break;
case SUMD_DECODE_STATE_GOT_STATE:
if (byte >= 2 && byte <= SUMD_MAX_CHANNELS) {
_rxpacket.length = byte;
if (_sumd) {
_crc16 = sumd_crc16(_crc16, byte);
} else {
_crc8 = sumd_crc8(_crc8, byte);
}
_rxlen++;
_decode_state = SUMD_DECODE_STATE_GOT_LEN;
if (_debug) {
printf(" SUMD_DECODE_STATE_GOT_LEN: %x (%d) \n", byte, byte) ;
}
} else {
_decode_state = SUMD_DECODE_STATE_UNSYNCED;
}
break;
case SUMD_DECODE_STATE_GOT_LEN:
_rxpacket.sumd_data[_rxlen] = byte;
if (_sumd) {
_crc16 = sumd_crc16(_crc16, byte);
} else {
_crc8 = sumd_crc8(_crc8, byte);
}
_rxlen++;
if (_rxlen <= ((_rxpacket.length * 2))) {
if (_debug) {
printf(" SUMD_DECODE_STATE_GOT_DATA[%d]: %x\n", _rxlen - 2, byte) ;
}
} else {
_decode_state = SUMD_DECODE_STATE_GOT_DATA;
if (_debug) {
printf(" SUMD_DECODE_STATE_GOT_DATA -- finish --\n") ;
}
}
break;
case SUMD_DECODE_STATE_GOT_DATA:
_rxpacket.crc16_high = byte;
if (_debug) {
printf(" SUMD_DECODE_STATE_GOT_CRC16[1]: %x [%x]\n", byte, ((_crc16 >> 8) & 0xff)) ;
}
if (_sumd) {
_decode_state = SUMD_DECODE_STATE_GOT_CRC;
} else {
_decode_state = SUMD_DECODE_STATE_GOT_CRC16_BYTE_1;
}
break;
case SUMD_DECODE_STATE_GOT_CRC16_BYTE_1:
_rxpacket.crc16_low = byte;
if (_debug) {
printf(" SUMD_DECODE_STATE_GOT_CRC16[2]: %x [%x]\n", byte, (_crc16 & 0xff)) ;
}
_decode_state = SUMD_DECODE_STATE_GOT_CRC16_BYTE_2;
break;
case SUMD_DECODE_STATE_GOT_CRC16_BYTE_2:
_rxpacket.telemetry = byte;
if (_debug) {
printf(" SUMD_DECODE_STATE_GOT_SUMH_TELEMETRY: %x\n", byte) ;
}
_decode_state = SUMD_DECODE_STATE_GOT_CRC;
break;
case SUMD_DECODE_STATE_GOT_CRC:
if (_sumd) {
_rxpacket.crc16_low = byte;
if (_debug) {
printf(" SUMD_DECODE_STATE_GOT_CRC[2]: %x [%x]\n\n", byte, (_crc16 & 0xff)) ;
}
if (_crc16 == (uint16_t)(_rxpacket.crc16_high << 8) + _rxpacket.crc16_low) {
_crcOK = true;
}
} else {
_rxpacket.crc8 = byte;
if (_debug) {
printf(" SUMD_DECODE_STATE_GOT_CRC8_SUMH: %x [%x]\n\n", byte, _crc8) ;
}
if (_crc8 == _rxpacket.crc8) {
_crcOK = true;
}
}
if (_crcOK) {
if (_debug) {
printf(" CRC - OK \n") ;
}
if (_sumd) {
if (_debug) {
printf(" Got valid SUMD Packet\n") ;
}
} else {
if (_debug) {
printf(" Got valid SUMH Packet\n") ;
}
}
if (_debug) {
printf(" RXLEN: %d [Chans: %d] \n\n", _rxlen - 1, (_rxlen - 1) / 2) ;
}
ret = 0;
unsigned i;
uint8_t _cnt = *rx_count + 1;
*rx_count = _cnt;
*rssi = 100;
/* received Channels */
if ((uint16_t)_rxpacket.length > max_chan_count) {
_rxpacket.length = (uint8_t) max_chan_count;
}
*channel_count = (uint16_t)_rxpacket.length;
/* decode the actual packet */
/* reorder first 4 channels */
/* ch1 = roll -> sumd = ch2 */
channels[0] = (uint16_t)((_rxpacket.sumd_data[1 * 2 + 1] << 8) | _rxpacket.sumd_data[1 * 2 + 2]) >> 3;
/* ch2 = pitch -> sumd = ch2 */
channels[1] = (uint16_t)((_rxpacket.sumd_data[2 * 2 + 1] << 8) | _rxpacket.sumd_data[2 * 2 + 2]) >> 3;
/* ch3 = throttle -> sumd = ch2 */
channels[2] = (uint16_t)((_rxpacket.sumd_data[0 * 2 + 1] << 8) | _rxpacket.sumd_data[0 * 2 + 2]) >> 3;
/* ch4 = yaw -> sumd = ch2 */
channels[3] = (uint16_t)((_rxpacket.sumd_data[3 * 2 + 1] << 8) | _rxpacket.sumd_data[3 * 2 + 2]) >> 3;
/* we start at channel 5(index 4) */
unsigned chan_index = 4;
for (i = 4; i < _rxpacket.length; i++) {
if (_debug) {
printf("ch[%d] : %x %x [ %x %d ]\n", i + 1, _rxpacket.sumd_data[i * 2 + 1], _rxpacket.sumd_data[i * 2 + 2],
((_rxpacket.sumd_data[i * 2 + 1] << 8) | _rxpacket.sumd_data[i * 2 + 2]) >> 3,
((_rxpacket.sumd_data[i * 2 + 1] << 8) | _rxpacket.sumd_data[i * 2 + 2]) >> 3);
}
channels[chan_index] = (uint16_t)((_rxpacket.sumd_data[i * 2 + 1] << 8) | _rxpacket.sumd_data[i * 2 + 2]) >> 3;
/* convert values to 1000-2000 ppm encoding in a not too sloppy fashion */
//channels[chan_index] = (uint16_t)(channels[chan_index] * SUMD_SCALE_FACTOR + .5f) + SUMD_SCALE_OFFSET;
chan_index++;
}
} else {
/* decoding failed */
ret = 4;
if (_debug) {
printf(" CRC - fail \n") ;
}
}
_decode_state = SUMD_DECODE_STATE_UNSYNCED;
break;
}
return ret;
}
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