ardupilot/libraries/SITL/SIM_PS_RPLidarA2.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/>.
 */
/*
  Simulator for the RPLidarA2 proximity sensor
*/

#include "SIM_PS_RPLidarA2.h"

#include <GCS_MAVLink/GCS.h>
#include <stdio.h>
#include <errno.h>

using namespace SITL;

uint32_t PS_RPLidarA2::packet_for_location(const Location &location,
                                           uint8_t *data,
                                           uint8_t buflen)
{
    return 0;
}

void PS_RPLidarA2::move_preamble_in_buffer()
{
    uint8_t i;
    for (i=0; i<_buflen; i++) {
        if ((uint8_t)_buffer[i] == PREAMBLE) {
            break;
        }
    }
    if (i == 0) {
        return;
    }
    memmove(_buffer, &_buffer[i], _buflen-i);
    _buflen = _buflen - i;
}

void PS_RPLidarA2::update_input()
{
    const ssize_t n = read_from_autopilot(&_buffer[_buflen], ARRAY_SIZE(_buffer) - _buflen - 1);
    if (n < 0) {
        // TODO: do better here
        if (errno != EAGAIN && errno != EWOULDBLOCK && errno != 0) {
            AP_HAL::panic("Failed to read from autopilot");
        }
    } else {
        _buflen += n;
    }

    switch (_inputstate) {
    case InputState::WAITING_FOR_PREAMBLE:
        move_preamble_in_buffer();
        if (_buflen == 0) {
            return;
        }
        set_inputstate(InputState::GOT_PREAMBLE);
        // consume the preamble:
        memmove(_buffer, &_buffer[1], _buflen-1);
        _buflen--;
        FALLTHROUGH;
    case InputState::GOT_PREAMBLE:
        if (_buflen == 0) {
            return;
        }
        switch ((Command)_buffer[0]) {
        case Command::STOP:
            // consume the command:
            memmove(_buffer, &_buffer[1], _buflen-1);
            _buflen--;
            set_inputstate(InputState::WAITING_FOR_PREAMBLE);
            set_state(State::IDLE);
            return;
        case Command::SCAN:
            // consume the command:
            memmove(_buffer, &_buffer[1], _buflen-1);
            _buflen--;
            send_response_descriptor(0x05, SendMode::SRMR, DataType::Unknown81);
            set_inputstate(InputState::WAITING_FOR_PREAMBLE);
            set_state(State::SCANNING);
            return;
        case Command::GET_HEALTH: {
            // consume the command:
            memmove(_buffer, &_buffer[1], _buflen-1);
            _buflen--;
            send_response_descriptor(0x03, SendMode::SRSR, DataType::Unknown06);
            // now send the health:
            const uint8_t health[3] {}; // all zeros fine for now
            const ssize_t ret = write_to_autopilot((const char*)health, ARRAY_SIZE(health));
            if (ret != ARRAY_SIZE(health)) {
                abort();
            }
            set_inputstate(InputState::WAITING_FOR_PREAMBLE);
            return;
        }
        case Command::FORCE_SCAN:
            abort();
        case Command::RESET:
            // consume the command:
            memmove(_buffer, &_buffer[1], _buflen-1);
            _buflen--;
            set_inputstate(InputState::RESETTING_START);
            return;
        default:
            AP_HAL::panic("Bad command received (%02x)", (uint8_t)_buffer[0]);
        }
    case InputState::RESETTING_START:
        _firmware_info_offset = 0;
        set_inputstate(InputState::RESETTING_SEND_FIRMWARE_INFO);
        FALLTHROUGH;
    case InputState::RESETTING_SEND_FIRMWARE_INFO: {
        const ssize_t written = write_to_autopilot(&FIRMWARE_INFO[_firmware_info_offset], strlen(FIRMWARE_INFO) - _firmware_info_offset);
        if (written <= 0) {
            AP_HAL::panic("Failed to write to autopilot");
        }
        _firmware_info_offset += written;
        if (_firmware_info_offset < strlen(FIRMWARE_INFO)) {
            return;
        }
        set_inputstate(InputState::WAITING_FOR_PREAMBLE);
        return;
    }
    }
}

void PS_RPLidarA2::update_output_scan(const Location &location)
{
    const uint32_t now = AP_HAL::millis();
    if (last_scan_output_time_ms == 0) {
        last_scan_output_time_ms = now;
        return;
    }
    const uint32_t time_delta = (now - last_scan_output_time_ms);

    const uint32_t samples_per_second = 1000;
    const float samples_per_ms = samples_per_second / 1000.0f;
    const uint32_t sample_count = time_delta / samples_per_ms;
    const float degrees_per_ms = 3600 / 1000.0f;
    const float degrees_per_sample = degrees_per_ms / samples_per_ms;

//    ::fprintf(stderr, "Packing %u samples in for %ums interval (%f degrees/sample)\n", sample_count, time_delta, degrees_per_sample);

    last_scan_output_time_ms += sample_count/samples_per_ms;

    for (uint32_t i=0; i<sample_count; i++) {
        const float current_degrees_bf = fmod((last_degrees_bf + degrees_per_sample), 360.0f);
        const uint8_t quality = 17; // random number
        const uint16_t angle_q6 = current_degrees_bf * 64;
        const bool is_start_packet = current_degrees_bf < last_degrees_bf;
        last_degrees_bf = current_degrees_bf;


        const float MAX_RANGE = 16.0f;
        float distance = measure_distance_at_angle_bf(location, current_degrees_bf);
        // ::fprintf(stderr, "SIM: %f=%fm\n", current_degrees_bf, distance);
        if (distance > MAX_RANGE) {
            // sensor returns zero for out-of-range
            distance = 0.0f;
        }
        const uint16_t distance_q2 = (distance*1000 * 4); // m->mm and *4

        struct PACKED  {
            uint8_t startbit      : 1;            ///< on the first revolution 1 else 0
            uint8_t not_startbit  : 1;            ///< complementary to startbit
            uint8_t quality       : 6;            ///< Related the reflected laser pulse strength
            uint8_t checkbit      : 1;            ///< always set to 1
            uint16_t angle_q6     : 15;           ///< Actual heading = angle_q6/64.0 Degree
            uint16_t distance_q2  : 16;           ///< Actual Distance = distance_q2/4.0 mm
        } send_buffer;
        send_buffer.startbit = is_start_packet;
        send_buffer.not_startbit = !is_start_packet;
        send_buffer.quality = quality;
        send_buffer.checkbit = 1;
        send_buffer.angle_q6 = angle_q6;
        send_buffer.distance_q2 = distance_q2;

        static_assert(sizeof(send_buffer) == 5, "send_buffer correct size");

        const ssize_t ret = write_to_autopilot((const char*)&send_buffer, sizeof(send_buffer));
        if (ret != sizeof(send_buffer)) {
            abort();
        }
    }
}

void PS_RPLidarA2::update_output(const Location &location)
{
    switch (_state) {
    case State::IDLE:
        return;
    case State::SCANNING:
        update_output_scan(location);
        return;
    }
}

void PS_RPLidarA2::update(const Location &location)
{
    update_input();
    update_output(location);
}


void PS_RPLidarA2::send_response_descriptor(uint32_t data_response_length, SendMode sendmode, DataType datatype)
{
    const uint8_t send_buffer[] = {
        0xA5,
        0x5A,
        uint8_t((data_response_length >> 0) & 0xff),
        uint8_t((data_response_length >>  8) & 0xff),
        uint8_t((data_response_length >> 16) & 0xff),
        uint8_t(((data_response_length >> 24) & 0xff) | (uint8_t) sendmode),
        (uint8_t)datatype
    };
    static_assert(ARRAY_SIZE(send_buffer) == 7, "send_buffer correct size");

    const ssize_t ret = write_to_autopilot((const char*)send_buffer, ARRAY_SIZE(send_buffer));
    if (ret != ARRAY_SIZE(send_buffer)) {
        abort();
    }
}