ardupilot/libraries/AP_RCProtocol/AP_RCProtocol_SRXL2.cpp

/*
   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
/*
  SRXL2 protocol decoder using Horizon Hobby's open source library https://github.com/SpektrumRC/SRXL2
  Code by Andy Piper
 */

#include "AP_RCProtocol_config.h"

#if AP_RCPROTOCOL_SRXL2_ENABLED

#include "AP_RCProtocol.h"
#include "AP_RCProtocol_SRXL2.h"
#include <AP_Math/AP_Math.h>
#include <AP_RCTelemetry/AP_Spektrum_Telem.h>
#include <AP_Vehicle/AP_Vehicle_Type.h>
#include <AP_HAL/utility/sparse-endian.h>
#include <AP_VideoTX/AP_VideoTX.h>

#include "spm_srxl.h"

extern const AP_HAL::HAL& hal;
//#define SRXL2_DEBUG
#ifdef SRXL2_DEBUG
# define debug(fmt, args...)	hal.console->printf("SRXL2:" fmt "\n", ##args)
#else
# define debug(fmt, args...)	do {} while(0)
#endif

AP_RCProtocol_SRXL2* AP_RCProtocol_SRXL2::_singleton;

AP_RCProtocol_SRXL2::AP_RCProtocol_SRXL2(AP_RCProtocol &_frontend) : AP_RCProtocol_Backend(_frontend)
{
#if !APM_BUILD_TYPE(APM_BUILD_UNKNOWN)
    if (_singleton != nullptr) {
        AP_HAL::panic("Duplicate SRXL2 handler\n");
    }

    _singleton = this;
#else
    if (_singleton == nullptr) {
        _singleton = this;
    }
#endif
}

void AP_RCProtocol_SRXL2::_bootstrap(uint8_t device_id)
{
    if (_device_id == device_id) {
        return;
    }

    // Init the local SRXL device
    if (!srxlInitDevice(device_id, SRXL_DEVICE_PRIORITY, SRXL_DEVICE_INFO, device_id)) {
        AP_HAL::panic("Failed to initialize SRXL2 device\n");
    }

    // Init the SRXL bus: The bus index must always be < SRXL_NUM_OF_BUSES -- in this case, it can only be 0
    if (!srxlInitBus(0, 0, SRXL_SUPPORTED_BAUD_RATES)) {
        AP_HAL::panic("Failed to initialize SRXL2 bus\n");
    }

    _device_id = device_id;

    debug("Bootstrapped as 0x%x", _device_id);
}

AP_RCProtocol_SRXL2::~AP_RCProtocol_SRXL2() {
    _singleton = nullptr;
}

void AP_RCProtocol_SRXL2::_process_byte(uint32_t timestamp_us, uint8_t byte)
{
    if (_decode_state == STATE_IDLE) {
        switch (byte) {
        case SPEKTRUM_SRXL_ID:
            _decode_state = STATE_NEW;
            break;
        default:
            _decode_state = STATE_IDLE;
            return;
        }
        _frame_len_full = 0U;
        _buflen = 0;
        _decode_state_next = STATE_IDLE;
    }

    switch (_decode_state) {
    case STATE_NEW:  // buffer header byte and prepare for frame reception and decoding
        _buffer[0U]=byte;
        _buflen = 1U;
        _decode_state_next = STATE_COLLECT;
        break;

    case STATE_COLLECT: // receive all bytes. After reception decode frame and provide rc channel information to FMU
        _buffer[_buflen] = byte;
        _buflen++;

        // need a header to get the length
        if (_buflen < SRXL2_HEADER_LEN) {
            return;
        }

        // parse the length
        if (_buflen == SRXL2_HEADER_LEN) {
            _frame_len_full = _buffer[2];
            // check for garbage frame
            if (_frame_len_full > SRXL2_FRAMELEN_MAX) {
                _decode_state = STATE_IDLE;
                _buflen = 0;
                _frame_len_full = 0;
            }
            return;
        }

        if (_buflen > _frame_len_full) {
            // a logic bug in the state machine, this shouldn't happen
            _decode_state = STATE_IDLE;
            _buflen = 0;
            _frame_len_full = 0;
            return;
        }

        if (_buflen == _frame_len_full) {
            log_data(AP_RCProtocol::SRXL2, timestamp_us, _buffer, _buflen);
            // we got a full frame but never handshaked before
            if (!is_bootstrapped()) {
                if (_buffer[1] == 0x21) {
                    _bootstrap(SRXL_DEVICE_ID);
                    _last_handshake_ms = timestamp_us / 1000;
                } else {
                    // not a handshake frame so reset without initializing the SRXL2 engine
                    _decode_state = STATE_IDLE;
                    _buflen = 0;
                    _frame_len_full = 0;
                    return;
                }
            }
            // Try to parse SRXL packet -- this internally calls srxlRun() after packet is parsed and resets timeout
            if (srxlParsePacket(0, _buffer, _frame_len_full)) {
                add_input(ARRAY_SIZE(_channels), _channels, _in_failsafe, _new_rssi);
            }
            _last_run_ms = AP_HAL::millis();

            _decode_state_next = STATE_IDLE;
            _buflen = 0;
        } else {
            _decode_state_next = STATE_COLLECT;
        }
        break;

    default:
        break;
    }

    _decode_state = _decode_state_next;
}

void AP_RCProtocol_SRXL2::update(void)
{
    // on a SPM4650 with telemetry the frame rate is 91Hz equating to around 10ms per frame
    // however only half of them can return telemetry, so the maximum telemetry rate is 46Hz
    // also update() is run immediately after check_added_uart() and so in general the delay is < 5ms
    // to be safe we will only run if the timeout exceeds 50ms
    if (_last_run_ms > 0) {
        uint32_t now = AP_HAL::millis();
        // there have been no updates since we were last called
        const uint32_t delay = now - _last_run_ms;
        if (delay > 50) {
            srxlRun(0, delay);
            _last_run_ms = now;
        }
    }
}

// capture SRXL2 encoded values
void AP_RCProtocol_SRXL2::capture_scaled_input(const uint8_t *values_p, bool in_failsafe, int16_t new_rssi)
{
    _in_failsafe = in_failsafe;
    // AP rssi: -1 for unknown, 0 for no link, 255 for maximum link
    // SRXL2 rssi: -ve rssi in dBM, +ve rssi in percentage
    if (new_rssi >= 0) {
        _new_rssi = new_rssi * 255 / 100;
    }

    for (uint8_t i = 0; i < ARRAY_SIZE(_channels); i++) {
        /*
         * Store the decoded channel into the R/C input buffer, taking into
         * account the different ideas about channel assignement that we have.
         *
         * Specifically, the first four channels in rc_channel_data are roll, pitch, thrust, yaw,
         * but the first four channels from the DSM receiver are thrust, roll, pitch, yaw.
         */
        uint8_t channel = i;
        switch (channel) {
        case 0:
            channel = 2;
            break;

        case 1:
            channel = 0;
            break;

        case 2:
            channel = 1;
            break;

        default:
            break;
        }
        /*
         * Each channel data value is sent as an unsigned 16-bit value from 0 to 65532 (0xFFFC)
         * with 32768 (0x8000) representing "Servo Center". The channel value must be bit-shifted
         * to the right to match the applications's accepted resolution.
         *
         * So here we scale to DSMX-2048 and then use our regular Spektrum conversion.
         */
        const uint16_t v = le16toh_ptr(&values_p[i*2]);
        _channels[channel] = ((int32_t)(v >> 5) * 1194) / 2048 + 903;
    }
}


// start bind on DSM satellites
void AP_RCProtocol_SRXL2::start_bind(void)
{
    srxlEnterBind(DSMX_11MS, true);
}

// process a byte provided by a uart
void AP_RCProtocol_SRXL2::process_byte(uint8_t byte, uint32_t baudrate)
{
    if (baudrate != 115200) {
        return;
    }

    _process_byte(AP_HAL::micros(), byte);
}

// handshake
void AP_RCProtocol_SRXL2::process_handshake(uint32_t baudrate)
{
    // only bootstrap if only SRXL2 is enabled
    if (baudrate != 115200 || (get_rc_protocols_mask() & ~(1U<<(uint8_t(AP_RCProtocol::SRXL2)+1)))) {
        _handshake_start_ms = 0;
        return;
    }
    uint32_t now = AP_HAL::millis();

    // record the time of the first request in this cycle
    if (_handshake_start_ms == 0) {
        _handshake_start_ms = now;
        // it seems the handshake protocol only sets the baudrate after receiving data
        // since we are sending data unprompted make sure that the uart is set up correctly
        change_baud_rate(baudrate);
    }

    // we have not bootstrapped and attempts to listen first have failed
    // we should receive a handshake request within the first 250ms
    if (!is_bootstrapped() && now - _handshake_start_ms > 250) {
        _bootstrap(SRXL_DEVICE_ID_BASE_RX);
    }

    // certain RXs (e.g. AR620) are "listen-only" - they require the flight controller to initiate
    // a handshake in order to switch to SRXL2 mode. This requires that we send data on the UART even
    // if we have not decoded SRXL2 (recently). We try this every 50ms.
    if (now - _handshake_start_ms > 250 && (_last_handshake_ms == 0 || (now - _last_run_ms > 50 && now - _last_handshake_ms > 50))) {
        _in_bootstrap_or_failsafe = true;
        srxlRun(0, 50); // 50 is a magic number at which the handshake protocol is initiated
        _in_bootstrap_or_failsafe = false;
        _last_handshake_ms = now;
    }
}

// send data to the uart
void AP_RCProtocol_SRXL2::send_on_uart(uint8_t* pBuffer, uint8_t length)
{
    AP_HAL::UARTDriver* uart = get_available_UART();

    if (uart != nullptr && uart->is_initialized()) {
        // check that we haven't been too slow in responding to the new UART data. If we respond too late then we will
        // corrupt the next incoming control frame. incoming packets at max 800bits @91Hz @115k baud gives total budget of 11ms 
        // per packet of which we need 7ms to receive a packet. outgoing packets are 220 bits which require 2ms to send
        // leaving at most 2ms of delay that can be tolerated
        uint64_t tend = uart->receive_time_constraint_us(1);
        uint64_t now = AP_HAL::micros64();
        uint64_t tdelay = now - tend;
        if (tdelay > 2000 && !_in_bootstrap_or_failsafe) {
            // we've been too slow in responding
            return;
        }
        // debug telemetry packets
        if (pBuffer[1] == 0x80 && pBuffer[4] != 0) {
            debug("0x%x 0x%x 0x%x 0x%x 0x%x 0x%x 0x%x 0x%x 0x%x 0x%x: %s",
                pBuffer[0], pBuffer[1], pBuffer[2], pBuffer[3], pBuffer[4], pBuffer[5], pBuffer[6], pBuffer[7], pBuffer[8], pBuffer[9], &pBuffer[7]);
        }
        uart->write(pBuffer, length);
    }
}

// change the uart baud rate
void AP_RCProtocol_SRXL2::change_baud_rate(uint32_t baudrate)
{
    AP_HAL::UARTDriver* uart = get_available_UART();
    if (uart != nullptr) {
        uart->begin(baudrate);
        uart->set_flow_control(AP_HAL::UARTDriver::FLOW_CONTROL_DISABLE);
        uart->set_unbuffered_writes(true);
    }
}

// SRXL2 library callbacks below

// User-provided routine to change the baud rate settings on the given UART:
// uart - the same uint8_t value as the uart parameter passed to srxlInit()
// baudRate - the actual baud rate (currently either 115200 or 400000)
void srxlChangeBaudRate(uint8_t uart, uint32_t baudRate)
{
    AP_RCProtocol_SRXL2* srxl2 = AP_RCProtocol_SRXL2::get_singleton();

    if (srxl2 != nullptr) {
        srxl2->change_baud_rate(baudRate);
    }
}

// User-provided routine to actually transmit a packet on the given UART:
// uart - the same uint8_t value as the uart parameter passed to srxlInit()
// pBuffer - a pointer to an array of uint8_t values to send over the UART
// length - the number of bytes contained in pBuffer that should be sent
void srxlSendOnUart(uint8_t uart, uint8_t* pBuffer, uint8_t length)
{
    AP_RCProtocol_SRXL2* srxl2 = AP_RCProtocol_SRXL2::get_singleton();

    if (srxl2 != nullptr) {
        srxl2->send_on_uart(pBuffer, length);
    }
}

// User-provided callback routine to fill in the telemetry data to send to the master when requested:
// pTelemetryData - a pointer to the 16-byte SrxlTelemetryData transmit buffer to populate
// NOTE: srxlTelemData is available as a global variable, so the memcpy line commented out below
// could be used if you would prefer to just populate that with the next outgoing telemetry packet.
void srxlFillTelemetry(SrxlTelemetryData* pTelemetryData)
{
#if HAL_SPEKTRUM_TELEM_ENABLED && !APM_BUILD_TYPE(APM_BUILD_iofirmware)
    AP_Spektrum_Telem::get_telem_data(pTelemetryData->raw);
#endif
}

// User-provided callback routine that is called whenever a control data packet is received:
// pChannelData - a pointer to the received SrxlChannelData structure for manual parsing
// isFailsafe - true if channel data is set to failsafe values, else false.
// this is called from within srxlParsePacket() and before the SRXL2 state machine has been run
// so be very careful to only do local operations
void srxlReceivedChannelData(SrxlChannelData* pChannelData, bool isFailsafe)
{
    AP_RCProtocol_SRXL2* srxl2 = AP_RCProtocol_SRXL2::get_singleton();

    if (srxl2 == nullptr) {
        return;
    }

    if (isFailsafe) {
        srxl2->capture_scaled_input((const uint8_t *)pChannelData->values, true, pChannelData->rssi);
    } else {
        srxl2->capture_scaled_input((const uint8_t *)srxlChData.values, false, srxlChData.rssi);
    }
}

// User-provided callback routine to handle reception of a bound data report (either requested or unprompted).
// Return true if you want this bind information set automatically for all other receivers on all SRXL buses.
bool srxlOnBind(SrxlFullID device, SrxlBindData info)
{
    return true;
}

// User-provided callback routine to handle reception of a VTX control packet.
void srxlOnVtx(SrxlVtxData* pVtxData)
{
#if AP_VIDEOTX_ENABLED
    AP_RCProtocol_Backend::configure_vtx(pVtxData->band, pVtxData->channel, pVtxData->power, pVtxData->pit);
#endif
}

#endif  // AP_RCPROTOCOL_SRXL2_ENABLED