mirror of https://github.com/ArduPilot/ardupilot
348 lines
13 KiB
C++
348 lines
13 KiB
C++
/*
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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/*
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SRXL protocol decoder, tested against AR7700 SRXL port
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Andrew Tridgell, September 2016
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Co author: Roman Kirchner, September 2016
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- 2016.10.23: SRXL variant V1 sucessfully (Testbench and Pixhawk/MissionPlanner) tested with RX-9-DR M-LINK (SW v1.26)
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*/
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#include "AP_RCProtocol_SRXL.h"
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// #define SUMD_DEBUG
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extern const AP_HAL::HAL& hal;
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/**
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* This function calculates the 16bit crc as used throughout the srxl protocol variants
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*
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* This function is intended to be called whenever a new byte shall be added to the crc.
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* Simply provide the old crc and the new data byte and the function return the new crc value.
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*
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* To start a new crc calculation for a new srxl frame, provide parameter crc=0 and the first byte of the frame.
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*
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* @param[in] crc - start value for crc
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* @param[in] new_byte - byte that shall be included in crc calculation
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* @return calculated crc
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*/
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uint16_t AP_RCProtocol_SRXL::srxl_crc16(uint16_t crc, uint8_t new_byte)
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{
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uint8_t loop;
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crc = crc ^ (uint16_t)new_byte << 8;
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for (loop = 0; loop < 8; loop++) {
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crc = (crc & 0x8000) ? (crc << 1) ^ 0x1021 : (crc << 1);
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}
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return crc;
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}
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void AP_RCProtocol_SRXL::process_pulse(uint32_t width_s0, uint32_t width_s1)
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{
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// convert to bit widths, allowing for up to about 4usec error, assuming 115200 bps
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uint16_t bits_s0 = ((width_s0+4)*(uint32_t)115200) / 1000000;
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uint16_t bits_s1 = ((width_s1+4)*(uint32_t)115200) / 1000000;
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uint8_t bit_ofs, byte_ofs;
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uint16_t nbits;
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if (bits_s0 == 0 || bits_s1 == 0) {
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// invalid data
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goto reset;
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}
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byte_ofs = srxl_state.bit_ofs/10;
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bit_ofs = srxl_state.bit_ofs%10;
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if (byte_ofs >= SRXL_FRAMELEN_MAX) {
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goto reset;
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}
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// pull in the high bits
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nbits = bits_s0;
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if (nbits+bit_ofs > 10) {
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nbits = 10 - bit_ofs;
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}
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srxl_state.bytes[byte_ofs] |= ((1U<<nbits)-1) << bit_ofs;
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srxl_state.bit_ofs += nbits;
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bit_ofs += nbits;
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if (bits_s0 - nbits > 10) {
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// we have a full frame
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uint8_t byte;
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uint8_t i;
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for (i=0; i <= byte_ofs; i++) {
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// get raw data
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uint16_t v = srxl_state.bytes[i];
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// check start bit
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if ((v & 1) != 0) {
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break;
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}
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// check stop bits
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if ((v & 0x200) != 0x200) {
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break;
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}
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byte = ((v>>1) & 0xFF);
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process_byte(byte);
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}
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memset(&srxl_state, 0, sizeof(srxl_state));
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}
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byte_ofs = srxl_state.bit_ofs/10;
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bit_ofs = srxl_state.bit_ofs%10;
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if (bits_s1+bit_ofs > 10) {
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// invalid data
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goto reset;
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}
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// pull in the low bits
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srxl_state.bit_ofs += bits_s1;
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return;
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reset:
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memset(&srxl_state, 0, sizeof(srxl_state));
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}
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/**
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* Get RC channel information as microsecond pulsewidth representation from srxl version 1 and 2
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*
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* This function extracts RC channel information from srxl dataframe. The function expects the whole dataframe
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* in correct order in static array "buffer[SRXL_FRAMELEN_MAX]". After extracting all RC channel information, the data
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* is transferred to "values" array from parameter list. If the pixhawk does not support all channels from srxl datastream,
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* only supported number of channels will be refreshed.
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*
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* IMPORTANT SAFETY NOTICE: This function shall only be used after CRC has been successful.
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*
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* Structure of SRXL v1 dataframe --> 12 channels, 12 Bit per channel
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* Byte0: Header 0xA1
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* Byte1: Bits7-4:Empty Bits3-0:Channel1 MSB
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* Byte2: Bits7-0: Channel1 LSB
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* (....)
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* Byte23: Bits7-4:Empty Bits3-0:Channel12 MSB
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* Byte24: Bits7-0: Channel12 LSB
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* Byte25: CRC16 MSB
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* Byte26: CRC16 LSB
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*
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* Structure of SRXL v2 dataframe --> 16 channels, 12 Bit per channel
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* Byte0: Header 0xA2
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* Byte1: Bits7-4:Empty Bits3-0:Channel1 MSB
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* Byte2: Bits7-0: Channel1 LSB
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* (....)
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* Byte31: Bits7-4:Empty Bits3-0:Channel16 MSB
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* Byte32: Bits7-0: Channel16 LSB
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* Byte33: CRC16 MSB
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* Byte34: CRC16 LSB
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*
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* @param[in] max_values - maximum number of values supported by the pixhawk
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* @param[out] num_values - number of RC channels extracted from srxl frame
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* @param[out] values - array of RC channels with refreshed information as pulsewidth in microseconds Range: 800us - 2200us
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* @param[out] failsafe_state - true: RC-receiver is in failsafe state, false: RC-receiver is not in failsafe state
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* @retval 0 success
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*/
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int AP_RCProtocol_SRXL::srxl_channels_get_v1v2(uint16_t max_values, uint8_t *num_values, uint16_t *values, bool *failsafe_state)
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{
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uint8_t loop;
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uint32_t channel_raw_value;
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*num_values = (uint8_t)((frame_len_full - 3U)/2U);
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*failsafe_state = 0U; /* this protocol version does not support failsafe information */
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/* get data channel data from frame */
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for (loop=0U; loop < *num_values; loop++) {
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channel_raw_value = ((((uint32_t)buffer[loop*2U+1U])& 0x0000000FU) << 8U) | ((uint32_t)(buffer[loop*2U+2U])); /* get 12bit channel raw value from srxl datastream (mask out unused bits with 0x0000000F) */
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channels[loop] = (uint16_t)(((channel_raw_value * (uint32_t)1400U) >> 12U) + (uint32_t)800U); /* convert raw value to servo/esc signal pulsewidth in us */
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}
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/* provide channel data to FMU */
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if ((uint16_t)*num_values > max_values) {
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*num_values = (uint8_t)max_values;
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}
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memcpy(values, channels, (*num_values)*2);
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return 0; /* for srxl protocol version 1 and 2 it is not expected, that any error happen during decode process */
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}
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/**
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* Get RC channel information as microsecond pulsewidth representation from srxl version 5
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*
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* This function extracts RC channel information from srxl dataframe. The function expects the whole dataframe
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* in correct order in static array "buffer[SRXL_FRAMELEN_MAX]". After extracting all RC channel information, the data
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* is transferred to "values" array from parameter list. If the pixhawk does not support all channels from srxl datastream,
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* only supported number of channels will be refreshed.
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*
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* IMPORTANT SAFETY NOTICE: This function shall only be used after CRC has been successful.
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*
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* Structure of SRXL v5 dataframe
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* Byte0: Header 0xA5
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* Byte1 - Byte16: Payload
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* Byte17: CRC16 MSB
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* Byte18: CRC16 LSB
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*
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* @param[in] max_values - maximum number of values supported by the pixhawk
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* @param[out] num_values - number of RC channels extracted from srxl frame
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* @param[out] values - array of RC channels with refreshed information as pulsewidth in microseconds Range: 800us - 2200us
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* @param[out] failsafe_state - true: RC-receiver is in failsafe state, false: RC-receiver is not in failsafe state
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* @retval 0 success
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*/
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int AP_RCProtocol_SRXL::srxl_channels_get_v5(uint16_t max_values, uint8_t *num_values, uint16_t *values, bool *failsafe_state)
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{
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// up to 7 channel values per packet. Each channel value is 16
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// bits, with 11 bits of data and 4 bits of channel number. The
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// top bit indicates a special X-Plus channel
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for (uint8_t i=0; i<7; i++) {
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uint16_t b = buffer[i*2+2] << 8 | buffer[i*2+3];
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uint16_t c = b >> 11; // channel number
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int32_t v = b & 0x7FF;
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if (b & 0x8000) {
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continue;
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}
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if (c == 12) {
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// special handling for channel 12
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// see http://www.deviationtx.com/forum/protocol-development/2088-18-channels-for-dsm2-dsmx?start=40
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//printf("c12: 0x%x %02x %02x\n", (unsigned)(b>>9), (unsigned)buffer[0], (unsigned)buffer[1]);
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v = (b & 0x1FF) << 2;
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c = 10 + ((b >> 9) & 0x7);
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if (buffer[1] & 1) {
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c += 4;
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}
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} else if (c > 12) {
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// invalid
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v = 0;
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}
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// if channel number if greater than 16 then it is a X-Plus
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// channel. We don't yet know how to decode those. There is some information here:
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// http://www.deviationtx.com/forum/protocol-development/2088-18-channels-for-dsm2-dsmx?start=40
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// but we really need some sample data to confirm
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if (c < SRXL_MAX_CHANNELS) {
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v = (((v - 0x400) * 500) / 876) + 1500;
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channels[c] = v;
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if (c >= max_channels) {
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max_channels = c+1;
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}
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}
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//printf("%u:%u ", (unsigned)c, (unsigned)v);
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}
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//printf("\n");
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*num_values = max_channels;
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if (*num_values > max_values) {
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*num_values = max_values;
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}
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memcpy(values, channels, (*num_values)*2);
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// check failsafe bit, this goes low when connection to the
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// transmitter is lost
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*failsafe_state = ((buffer[1] & 2) == 0);
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// success
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return 0;
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}
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void AP_RCProtocol_SRXL::process_byte(uint8_t byte)
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{
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uint64_t timestamp_us = AP_HAL::micros64();
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/*----------------------------------------distinguish different srxl variants at the beginning of each frame---------------------------------------------- */
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/* Check if we have a new begin of a frame --> indicators: Time gap in datastream + SRXL header 0xA<VARIANT>*/
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if ((timestamp_us - last_data_us) >= SRXL_MIN_FRAMESPACE_US) {
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/* Now detect SRXL variant based on header */
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switch (byte) {
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case SRXL_HEADER_V1:
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frame_len_full = SRXL_FRAMELEN_V1;
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frame_header = SRXL_HEADER_V1;
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decode_state = STATE_NEW;
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break;
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case SRXL_HEADER_V2:
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frame_len_full = SRXL_FRAMELEN_V2;
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frame_header = SRXL_HEADER_V2;
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decode_state = STATE_NEW;
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break;
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case SRXL_HEADER_V5:
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frame_len_full = SRXL_FRAMELEN_V5;
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frame_header = SRXL_HEADER_V5;
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decode_state = STATE_NEW;
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break;
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default:
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frame_len_full = 0U;
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frame_header = SRXL_HEADER_NOT_IMPL;
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decode_state = STATE_IDLE;
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buflen = 0;
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return; /* protocol version not implemented --> no channel data --> unknown packet */
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}
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}
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/*--------------------------------------------collect all data from stream and decode-------------------------------------------------------*/
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switch (decode_state) {
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case STATE_NEW: /* buffer header byte and prepare for frame reception and decoding */
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buffer[0U]=byte;
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crc_fmu = srxl_crc16(0U,byte);
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buflen = 1U;
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decode_state_next = STATE_COLLECT;
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break;
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case STATE_COLLECT: /* receive all bytes. After reception decode frame and provide rc channel information to FMU */
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if (buflen >= frame_len_full) {
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// a logic bug in the state machine, this shouldn't happen
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decode_state = STATE_IDLE;
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buflen = 0;
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frame_len_full = 0;
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frame_header = SRXL_HEADER_NOT_IMPL;
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return;
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}
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buffer[buflen] = byte;
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buflen++;
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/* CRC not over last 2 frame bytes as these bytes inhabitate the crc */
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if (buflen <= (frame_len_full-2)) {
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crc_fmu = srxl_crc16(crc_fmu,byte);
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}
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if (buflen == frame_len_full) {
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/* CRC check here */
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crc_receiver = ((uint16_t)buffer[buflen-2] << 8U) | ((uint16_t)buffer[buflen-1]);
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if (crc_receiver == crc_fmu) {
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/* at this point buffer contains all frame data and crc is valid --> extract channel info according to SRXL variant */
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uint16_t values[SRXL_MAX_CHANNELS];
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uint8_t num_values;
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bool failsafe_state;
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switch (frame_header) {
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case SRXL_HEADER_V1:
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srxl_channels_get_v1v2(MAX_RCIN_CHANNELS, &num_values, values, &failsafe_state);
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add_input(num_values, values, failsafe_state);
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break;
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case SRXL_HEADER_V2:
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srxl_channels_get_v1v2(MAX_RCIN_CHANNELS, &num_values, values, &failsafe_state);
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add_input(num_values, values, failsafe_state);
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break;
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case SRXL_HEADER_V5:
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srxl_channels_get_v5(MAX_RCIN_CHANNELS, &num_values, values, &failsafe_state);
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add_input(num_values, values, failsafe_state);
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break;
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default:
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break;
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}
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}
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decode_state_next = STATE_IDLE; /* frame data buffering and decoding finished --> statemachine not in use until new header drops is */
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} else {
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/* frame not completely received --> frame data buffering still ongoing */
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decode_state_next = STATE_COLLECT;
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}
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break;
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default:
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break;
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} /* switch (decode_state) */
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decode_state = decode_state_next;
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last_data_us = timestamp_us;
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}
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