mirror of https://github.com/ArduPilot/ardupilot
454 lines
14 KiB
C++
454 lines
14 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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GHST protocol decoder based on betaflight implementation
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Code by Andy Piper
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*/
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#include "AP_RCProtocol_config.h"
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#if AP_RCPROTOCOL_GHST_ENABLED
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#define CRSF_BAUDRATE 416666U
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#include "AP_RCProtocol.h"
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#include "AP_RCProtocol_GHST.h"
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#include <AP_HAL/AP_HAL.h>
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#include <AP_Math/AP_Math.h>
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#include <AP_Math/crc.h>
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#include <AP_Vehicle/AP_Vehicle_Type.h>
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#include <AP_RCTelemetry/AP_GHST_Telem.h>
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#include <AP_SerialManager/AP_SerialManager.h>
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/*
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* GHST protocol
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*
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* GHST protocol uses a single wire half duplex uart connection.
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*
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* 420000 baud
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* not inverted
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* 8 Bit
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* 1 Stop bit
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* Big endian
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* Max frame size is 14 bytes
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*
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* Every frame has the structure:
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* <Device address><Frame length><Type><Payload><CRC>
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*
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* Device address: (uint8_t)
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* Frame length: length in bytes including Type (uint8_t)
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* Type: (uint8_t)
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* CRC: (uint8_t)
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*
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*/
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extern const AP_HAL::HAL& hal;
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//#define GHST_DEBUG
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//#define GHST_DEBUG_CHARS
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#ifdef GHST_DEBUG
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# define debug(fmt, args...) hal.console->printf("GHST: " fmt "\n", ##args)
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static const char* get_frame_type(uint8_t byte, uint8_t subtype = 0)
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{
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switch(byte) {
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case AP_RCProtocol_GHST::GHST_UL_RC_CHANS_HS4_5TO8:
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case AP_RCProtocol_GHST::GHST_UL_RC_CHANS_HS4_12_5TO8:
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return "RC5_8";
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case AP_RCProtocol_GHST::GHST_UL_RC_CHANS_HS4_9TO12:
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case AP_RCProtocol_GHST::GHST_UL_RC_CHANS_HS4_12_9TO12:
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return "RC9_12";
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case AP_RCProtocol_GHST::GHST_UL_RC_CHANS_HS4_13TO16:
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case AP_RCProtocol_GHST::GHST_UL_RC_CHANS_HS4_12_13TO16:
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return "RC13_16";
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case AP_RCProtocol_GHST::GHST_UL_RC_CHANS_RSSI:
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case AP_RCProtocol_GHST::GHST_UL_RC_CHANS_12_RSSI:
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return "RSSI";
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case AP_RCProtocol_GHST::GHST_UL_RC_VTX_CTRL:
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return "VTX_CTRL";
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case AP_RCProtocol_GHST::GHST_UL_VTX_SETUP:
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return "VTX_SETUP";
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}
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return "UNKNOWN";
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}
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#else
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# define debug(fmt, args...) do {} while(0)
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#endif
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#define GHST_MAX_FRAME_TIME_US 500U // 14 bytes @ 420k = ~450us
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#define GHST_FRAME_TIMEOUT_US 10000U // 10ms to account for scheduling delays
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#define GHST_INTER_FRAME_TIME_US 2000U // At fastest, frames are sent by the transmitter every 2 ms, 500 Hz
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#define GHST_HEADER_TYPE_LEN (GHST_HEADER_LEN + 1) // header length including type
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const uint16_t AP_RCProtocol_GHST::RF_MODE_RATES[RFMode::RF_MODE_MAX_MODES] = {
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55, 160, 250, 19, 250, 500, 150, 250,
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};
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AP_RCProtocol_GHST* AP_RCProtocol_GHST::_singleton;
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AP_RCProtocol_GHST::AP_RCProtocol_GHST(AP_RCProtocol &_frontend) : AP_RCProtocol_Backend(_frontend)
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{
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#if !APM_BUILD_TYPE(APM_BUILD_UNKNOWN)
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if (_singleton != nullptr) {
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AP_HAL::panic("Duplicate GHST handler");
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}
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_singleton = this;
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#else
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if (_singleton == nullptr) {
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_singleton = this;
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}
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#endif
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}
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AP_RCProtocol_GHST::~AP_RCProtocol_GHST() {
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_singleton = nullptr;
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}
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// get the protocol string
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const char* AP_RCProtocol_GHST::get_protocol_string() const {
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return "GHST";
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}
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// return the link rate as defined by the LinkStatistics
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uint16_t AP_RCProtocol_GHST::get_link_rate() const {
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return RF_MODE_RATES[_link_status.rf_mode - GHST_RF_MODE_NORMAL];
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}
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void AP_RCProtocol_GHST::_process_byte(uint32_t timestamp_us, uint8_t byte)
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{
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//debug("process_byte(0x%x)", byte);
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// we took too long decoding, start again - the RX will only send complete frames so this is unlikely to fail,
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// however thread scheduling can introduce longer delays even when the data has been received
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if (_frame_ofs > 0 && (timestamp_us - _start_frame_time_us) > GHST_FRAME_TIMEOUT_US) {
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_frame_ofs = 0;
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}
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// overflow check
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if (_frame_ofs >= GHST_FRAMELEN_MAX) {
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_frame_ofs = 0;
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}
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// start of a new frame
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if (_frame_ofs == 0) {
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_start_frame_time_us = timestamp_us;
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}
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add_to_buffer(_frame_ofs++, byte);
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// need a header to get the length
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if (_frame_ofs < GHST_HEADER_TYPE_LEN) {
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return;
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}
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// parse the length
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if (_frame_ofs == GHST_HEADER_TYPE_LEN) {
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_frame_crc = crc8_dvb_s2(0, _frame.type);
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// check for garbage frame
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if (_frame.length > GHST_FRAME_PAYLOAD_MAX) {
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_frame_ofs = 0;
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}
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return;
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}
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// update crc
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if (_frame_ofs < _frame.length + GHST_HEADER_LEN) {
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_frame_crc = crc8_dvb_s2(_frame_crc, byte);
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}
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// overflow check
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if (_frame_ofs > _frame.length + GHST_HEADER_LEN) {
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_frame_ofs = 0;
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return;
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}
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// decode whatever we got and expect
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if (_frame_ofs == _frame.length + GHST_HEADER_LEN) {
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log_data(AP_RCProtocol::GHST, timestamp_us, (const uint8_t*)&_frame, _frame_ofs - GHST_HEADER_LEN);
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// we consumed the partial frame, reset
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_frame_ofs = 0;
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// bad CRC (payload start is +1 from frame start, so need to subtract that from frame length to get index)
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if (_frame_crc != _frame.payload[_frame.length - 2]) {
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return;
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}
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_last_frame_time_us = _last_rx_frame_time_us = timestamp_us;
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// decode here
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if (decode_ghost_packet()) {
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_last_tx_frame_time_us = timestamp_us; // we have received a frame from the transmitter
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add_input(MAX_CHANNELS, _channels, false, _link_status.rssi, _link_status.link_quality);
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}
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}
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}
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void AP_RCProtocol_GHST::update(void)
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{
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}
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// write out a frame of any type
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bool AP_RCProtocol_GHST::write_frame(Frame* frame)
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{
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AP_HAL::UARTDriver *uart = get_current_UART();
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if (!uart) {
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return false;
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}
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// check that we haven't been too slow in responding to the new UART data. If we respond too late then we will
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// corrupt the next incoming control frame. incoming packets at max 126bits @500Hz @420k baud gives total budget of 2ms
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// per packet of which we need 300us to receive a packet. outgoing packets are 126bits which require 300us to send
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// leaving at most 1.4ms of delay that can be tolerated
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uint64_t tend = uart->receive_time_constraint_us(1);
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uint64_t now = AP_HAL::micros64();
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uint64_t tdelay = now - tend;
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if (tdelay > 1000) {
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// we've been too slow in responding
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return false;
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}
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// calculate crc
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uint8_t crc = crc8_dvb_s2(0, frame->type);
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for (uint8_t i = 0; i < frame->length - 2; i++) {
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crc = crc8_dvb_s2(crc, frame->payload[i]);
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}
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frame->payload[frame->length - 2] = crc;
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uart->write((uint8_t*)frame, frame->length + 2);
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uart->flush();
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#ifdef GHST_DEBUG
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hal.console->printf("GHST: writing %s:", get_frame_type(frame->type, frame->payload[0]));
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for (uint8_t i = 0; i < frame->length + 2; i++) {
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uint8_t val = ((uint8_t*)frame)[i];
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#ifdef GHST_DEBUG_CHARS
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if (val >= 32 && val <= 126) {
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hal.console->printf(" 0x%x '%c'", val, (char)val);
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} else {
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#endif
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hal.console->printf(" 0x%x", val);
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#ifdef GHST_DEBUG_CHARS
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}
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#endif
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}
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hal.console->printf("\n");
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#endif
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return true;
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}
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bool AP_RCProtocol_GHST::decode_ghost_packet()
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{
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#ifdef GHST_DEBUG
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hal.console->printf("GHST: received %s:", get_frame_type(_frame.type));
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uint8_t* fptr = (uint8_t*)&_frame;
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for (uint8_t i = 0; i < _frame.length + 2; i++) {
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#ifdef GHST_DEBUG_CHARS
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if (fptr[i] >= 32 && fptr[i] <= 126) {
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hal.console->printf(" 0x%x '%c'", fptr[i], (char)fptr[i]);
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} else {
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#endif
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hal.console->printf(" 0x%x", fptr[i]);
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#ifdef GHST_DEBUG_CHARS
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}
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#endif
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}
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hal.console->printf("\n");
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#endif
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const RadioFrame* radio_frame = (const RadioFrame*)(&_frame.payload);
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const Channels12Bit_4Chan* channels = &(radio_frame->channels);
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const uint8_t* lowres_channels = radio_frame->lowres_channels;
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// Scaling from Betaflight
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// Scaling 12bit channels (8bit channels in brackets)
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// OpenTx RC PWM (BF)
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// min -1024 0( 0) 988us
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// ctr 0 2048(128) 1500us
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// max 1024 4096(256) 2012us
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//
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// Scaling legacy (nearly 10bit)
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// derived from original SBus scaling, with slight correction for offset
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// now symmetrical around OpenTx 0 value
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// scaling is:
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// OpenTx RC PWM (BF)
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// min -1024 172( 22) 988us
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// ctr 0 992(124) 1500us
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// max 1024 1811(226) 2012us
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#define CHANNEL_RESCALE(x) (((5 * x) >> 2) - 430)
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#define CHANNEL_SCALE(x) (int32_t(x) / 4 + 988)
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#define CHANNEL_SCALE_LEGACY(x) CHANNEL_SCALE(CHANNEL_RESCALE(x))
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// legacy scaling
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if (_frame.type >= GHST_UL_RC_CHANS_HS4_5TO8 && _frame.type <= GHST_UL_RC_CHANS_RSSI) {
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_channels[0] = CHANNEL_SCALE_LEGACY(channels->ch0);
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_channels[1] = CHANNEL_SCALE_LEGACY(channels->ch1);
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_channels[2] = CHANNEL_SCALE_LEGACY(channels->ch2);
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_channels[3] = CHANNEL_SCALE_LEGACY(channels->ch3);
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} else {
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_channels[0] = CHANNEL_SCALE(channels->ch0);
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_channels[1] = CHANNEL_SCALE(channels->ch1);
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_channels[2] = CHANNEL_SCALE(channels->ch2);
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_channels[3] = CHANNEL_SCALE(channels->ch3);
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}
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#define CHANNEL_LR_RESCALE(x) (5 * x - 108)
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#define CHANNEL_LR_SCALE(x) (int32_t(x) * 2 + 988)
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#define CHANNEL_LR_SCALE_LEGACY(x) (CHANNEL_LR_RESCALE(x) + 988)
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switch (_frame.type) {
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case GHST_UL_RC_CHANS_HS4_5TO8:
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case GHST_UL_RC_CHANS_HS4_9TO12:
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case GHST_UL_RC_CHANS_HS4_13TO16: {
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uint8_t offset = (_frame.type - GHST_UL_RC_CHANS_HS4_5TO8 + 1) * 4;
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_channels[offset++] = CHANNEL_LR_SCALE_LEGACY(lowres_channels[0]);
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_channels[offset++] = CHANNEL_LR_SCALE_LEGACY(lowres_channels[1]);
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_channels[offset++] = CHANNEL_LR_SCALE_LEGACY(lowres_channels[2]);
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_channels[offset++] = CHANNEL_LR_SCALE_LEGACY(lowres_channels[3]);
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break;
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}
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case GHST_UL_RC_CHANS_HS4_12_5TO8:
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case GHST_UL_RC_CHANS_HS4_12_9TO12:
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case GHST_UL_RC_CHANS_HS4_12_13TO16: {
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uint8_t offset = (_frame.type - GHST_UL_RC_CHANS_HS4_12_5TO8 + 1) * 4;
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_channels[offset++] = CHANNEL_LR_SCALE(lowres_channels[0]);
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_channels[offset++] = CHANNEL_LR_SCALE(lowres_channels[1]);
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_channels[offset++] = CHANNEL_LR_SCALE(lowres_channels[2]);
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_channels[offset++] = CHANNEL_LR_SCALE(lowres_channels[3]);
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break;
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}
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case GHST_UL_RC_CHANS_RSSI:
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case GHST_UL_RC_CHANS_12_RSSI:
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process_link_stats_frame((uint8_t*)&_frame.payload);
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break;
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default:
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break;
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}
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#if AP_GHST_TELEM_ENABLED
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if (AP_GHST_Telem::process_frame(FrameType(_frame.type), (uint8_t*)&_frame.payload)) {
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process_telemetry();
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}
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#endif
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return true;
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}
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// send out telemetry
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bool AP_RCProtocol_GHST::process_telemetry(bool check_constraint)
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{
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AP_HAL::UARTDriver *uart = get_current_UART();
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if (!uart) {
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return false;
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}
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if (!telem_available) {
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#if AP_GHST_TELEM_ENABLED && !APM_BUILD_TYPE(APM_BUILD_iofirmware)
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if (AP_GHST_Telem::get_telem_data(&_telemetry_frame, is_tx_active())) {
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telem_available = true;
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} else {
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return false;
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}
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#else
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return false;
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#endif
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}
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if (!write_frame(&_telemetry_frame)) {
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return false;
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}
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// get fresh telem_data in the next call
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telem_available = false;
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return true;
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}
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// process link statistics to get RSSI
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void AP_RCProtocol_GHST::process_link_stats_frame(const void* data)
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{
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const LinkStatisticsFrame* link = (const LinkStatisticsFrame*)data;
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uint8_t rssi_dbm;
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rssi_dbm = link->rssi_dbm;
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_link_status.link_quality = link->link_quality;
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if (_use_lq_for_rssi) {
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_link_status.rssi = derive_scaled_lq_value(link->link_quality);
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} else{
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// AP rssi: -1 for unknown, 0 for no link, 255 for maximum link
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if (rssi_dbm < 50) {
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_link_status.rssi = 255;
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} else if (rssi_dbm > 120) {
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_link_status.rssi = 0;
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} else {
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// this is an approximation recommended by Remo from TBS
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_link_status.rssi = int16_t(roundf((1.0f - (rssi_dbm - 50.0f) / 70.0f) * 255.0f));
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}
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}
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_link_status.rf_mode = link->protocol;
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}
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bool AP_RCProtocol_GHST::is_telemetry_supported() const
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{
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return _link_status.rf_mode == AP_RCProtocol_GHST::GHST_RF_MODE_NORMAL
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|| _link_status.rf_mode == AP_RCProtocol_GHST::GHST_RF_MODE_RACE
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|| _link_status.rf_mode == AP_RCProtocol_GHST::GHST_RF_MODE_LR
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|| _link_status.rf_mode == AP_RCProtocol_GHST::GHST_RF_MODE_RACE250;
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}
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// process a byte provided by a uart
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void AP_RCProtocol_GHST::process_byte(uint8_t byte, uint32_t baudrate)
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{
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// reject RC data if we have been configured for standalone mode
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if (baudrate != CRSF_BAUDRATE && baudrate != GHST_BAUDRATE) {
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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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// change the bootstrap baud rate to ELRS standard if configured
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void AP_RCProtocol_GHST::process_handshake(uint32_t baudrate)
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{
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AP_HAL::UARTDriver *uart = get_current_UART();
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// only change the baudrate if we are bootstrapping CRSF
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if (uart == nullptr
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|| baudrate != CRSF_BAUDRATE
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|| baudrate == GHST_BAUDRATE
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|| uart->get_baud_rate() == GHST_BAUDRATE
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|| (get_rc_protocols_mask() & ((1U<<(uint8_t(AP_RCProtocol::GHST)+1))+1)) == 0) {
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return;
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}
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uart->begin(GHST_BAUDRATE);
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}
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//returns uplink link quality on 0-255 scale
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int16_t AP_RCProtocol_GHST::derive_scaled_lq_value(uint8_t uplink_lq)
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{
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return int16_t(roundf(constrain_float(uplink_lq*2.5f,0,255)));
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}
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namespace AP {
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AP_RCProtocol_GHST* ghost() {
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return AP_RCProtocol_GHST::get_singleton();
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}
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};
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#endif // AP_RCPROTOCOL_GHST_ENABLED
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