mirror of
https://github.com/ArduPilot/ardupilot.git
synced 2026-10-06 19:00:27 +08:00
Thomas Watson
7420edcb43
If the receiver sends less than four channels, the reordering step will use unspecified data from the input buffer as valid RC input values. The official minimum channel count from the protocol documentation is two. There is no risk of a buffer overread or overwrite, it is hard to believe a user would set up this configuration, and there is a relatively strong checksum which protects the channel count too. Therefore, an actual problem is unlikely. Fix by rejecting packets claiming to have less than four channels. This fix is zero-cost and removes any risk of garbage from such packets.
211 lines
7.5 KiB
C++
211 lines
7.5 KiB
C++
/*
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SUMD decoder, based on PX4Firmware/src/rc/lib/rc/sumd.c from PX4Firmware
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modified for use in AP_HAL_* by Andrew Tridgell
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*/
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/****************************************************************************
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*
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* Copyright (c) 2015 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 sumd.h
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*
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* RC protocol definition for Graupner HoTT transmitter (SUMD/SUMH Protocol)
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*
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* @author Marco Bauer <marco@wtns.de>
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*/
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#include "AP_RCProtocol_config.h"
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#if AP_RCPROTOCOL_SUMD_ENABLED
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#include "AP_RCProtocol_SUMD.h"
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#include <AP_Math/crc.h>
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#define SUMD_HEADER_LENGTH 3
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#define SUMD_HEADER_ID 0xA8
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#define SUMD_ID_SUMH 0x00
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#define SUMD_ID_SUMD 0x01
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#define SUMD_ID_FAILSAFE 0x81
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// #define SUMD_DEBUG
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extern const AP_HAL::HAL& hal;
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void AP_RCProtocol_SUMD::process_pulse(uint32_t width_s0, uint32_t width_s1)
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{
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uint8_t b;
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if (ss.process_pulse(width_s0, width_s1, b)) {
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_process_byte(ss.get_byte_timestamp_us(), b);
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}
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}
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void AP_RCProtocol_SUMD::_process_byte(uint32_t timestamp_us, uint8_t byte)
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{
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if (timestamp_us - last_packet_us > 5000U) {
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_decode_state = SUMD_DECODE_STATE_UNSYNCED;
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}
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switch (_decode_state) {
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case SUMD_DECODE_STATE_UNSYNCED:
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#ifdef SUMD_DEBUG
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hal.console->printf(" SUMD_DECODE_STATE_UNSYNCED \n") ;
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#endif
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if (byte == SUMD_HEADER_ID) {
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_rxlen = 0;
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_crc16 = crc_xmodem_update(0, byte);
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_decode_state = SUMD_DECODE_STATE_GOT_HEADER;
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#ifdef SUMD_DEBUG
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hal.console->printf(" SUMD_DECODE_STATE_GOT_HEADER: %x \n", byte) ;
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#endif
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last_packet_us = timestamp_us;
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}
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break;
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case SUMD_DECODE_STATE_GOT_HEADER:
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if ((byte == SUMD_ID_SUMD) || (byte == SUMD_ID_FAILSAFE)) {
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_rxpacket.status = byte;
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_crc16 = crc_xmodem_update(_crc16, byte);
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_decode_state = SUMD_DECODE_STATE_GOT_STATE;
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#ifdef SUMD_DEBUG
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hal.console->printf(" SUMD_DECODE_STATE_GOT_STATE: %x \n", byte) ;
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#endif
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} else {
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_decode_state = SUMD_DECODE_STATE_UNSYNCED;
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}
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break;
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case SUMD_DECODE_STATE_GOT_STATE:
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if (byte >= 4 && byte <= SUMD_MAX_CHANNELS) { // need at least 4 for reordering
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_rxpacket.length = byte;
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_crc16 = crc_xmodem_update(_crc16, byte);
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_rxlen++;
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_decode_state = SUMD_DECODE_STATE_GOT_LEN;
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#ifdef SUMD_DEBUG
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hal.console->printf(" SUMD_DECODE_STATE_GOT_LEN: %x (%d) \n", byte, byte) ;
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#endif
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} else {
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_decode_state = SUMD_DECODE_STATE_UNSYNCED;
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}
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break;
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case SUMD_DECODE_STATE_GOT_LEN:
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_rxpacket.sumd_data[_rxlen] = byte;
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_crc16 = crc_xmodem_update(_crc16, byte);
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_rxlen++;
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if (_rxlen <= ((_rxpacket.length * 2))) {
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#ifdef SUMD_DEBUG
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hal.console->printf(" SUMD_DECODE_STATE_GOT_DATA[%d]: %x\n", _rxlen - 2, byte) ;
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#endif
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} else {
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_decode_state = SUMD_DECODE_STATE_GOT_DATA;
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#ifdef SUMD_DEBUG
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hal.console->printf(" SUMD_DECODE_STATE_GOT_DATA -- finish --\n") ;
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#endif
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}
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break;
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case SUMD_DECODE_STATE_GOT_DATA:
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_rxpacket.crc16_high = byte;
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_decode_state = SUMD_DECODE_STATE_GOT_CRC;
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#ifdef SUMD_DEBUG
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hal.console->printf(" SUMD_DECODE_STATE_GOT_CRC16[1]: %x [%x]\n", byte, ((_crc16 >> 8) & 0xff)) ;
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#endif
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break;
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case SUMD_DECODE_STATE_GOT_CRC:
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#ifdef SUMD_DEBUG
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hal.console->printf(" SUMD_DECODE_STATE_GOT_CRC[2]: %x [%x]\n\n", byte, (_crc16 & 0xff)) ;
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#endif
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log_data(AP_RCProtocol::SUMD, timestamp_us, _rxpacket.sumd_data, _rxlen);
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if (_crc16 == (uint16_t)(_rxpacket.crc16_high << 8) + byte) {
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#ifdef SUMD_DEBUG
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hal.console->printf(" CRC - OK \n") ;
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hal.console->printf(" Got valid SUMD Packet\n") ;
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hal.console->printf(" RXLEN: %d [Chans: %d] \n\n", _rxlen - 1, (_rxlen - 1) / 2) ;
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#endif
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uint16_t values[SUMD_MAX_CHANNELS];
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/* received Channels */
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if ((uint16_t)_rxpacket.length > SUMD_MAX_CHANNELS) {
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_rxpacket.length = (uint8_t) SUMD_MAX_CHANNELS;
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}
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/* decode the actual packet */
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/* reorder first 4 channels */
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/* ch1 = roll -> sumd = ch2 */
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values[0] = (uint16_t)((_rxpacket.sumd_data[1 * 2 + 1] << 8) | _rxpacket.sumd_data[1 * 2 + 2]) >> 3;
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/* ch2 = pitch -> sumd = ch2 */
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values[1] = (uint16_t)((_rxpacket.sumd_data[2 * 2 + 1] << 8) | _rxpacket.sumd_data[2 * 2 + 2]) >> 3;
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/* ch3 = throttle -> sumd = ch2 */
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values[2] = (uint16_t)((_rxpacket.sumd_data[0 * 2 + 1] << 8) | _rxpacket.sumd_data[0 * 2 + 2]) >> 3;
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/* ch4 = yaw -> sumd = ch2 */
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values[3] = (uint16_t)((_rxpacket.sumd_data[3 * 2 + 1] << 8) | _rxpacket.sumd_data[3 * 2 + 2]) >> 3;
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/* we start at channel 5(index 4) */
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for (uint8_t i = 4; i < _rxpacket.length; i++) {
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#ifdef SUMD_DEBUG
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hal.console->printf("ch[%u] : %x %x [ %x %d ]\n", i + 1, _rxpacket.sumd_data[i * 2 + 1], _rxpacket.sumd_data[i * 2 + 2],
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((_rxpacket.sumd_data[i * 2 + 1] << 8) | _rxpacket.sumd_data[i * 2 + 2]) >> 3,
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((_rxpacket.sumd_data[i * 2 + 1] << 8) | _rxpacket.sumd_data[i * 2 + 2]) >> 3);
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#endif
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values[i] = (uint16_t)((_rxpacket.sumd_data[i * 2 + 1] << 8) | _rxpacket.sumd_data[i * 2 + 2]) >> 3;
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}
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add_input(_rxpacket.length, values, (_rxpacket.status == SUMD_ID_FAILSAFE));
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#ifdef SUMD_DEBUG
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} else {
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hal.console->printf(" CRC - fail 0x%X 0x%X\n", _crc16, (uint16_t)(_rxpacket.crc16_high << 8) + byte);
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#endif
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}
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_decode_state = SUMD_DECODE_STATE_UNSYNCED;
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break;
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}
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}
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void AP_RCProtocol_SUMD::process_byte(uint8_t byte, uint32_t baudrate)
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{
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if (baudrate != 115200) {
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return;
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}
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_process_byte(AP_HAL::micros(), byte);
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}
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#endif // AP_RCPROTOCOL_SUMD_ENABLED
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