rplidar_driver.cpp

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          http://www.mrpt.org/                          |
   |                                                                        |
   | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file     |
   | See: http://www.mrpt.org/Authors - All rights reserved.                |
   | Released under BSD License. See details in http://www.mrpt.org/License |
   +------------------------------------------------------------------------+ */
/*
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
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#include "sdkcommon.h"
#include "hal/abs_rxtx.h"
#include "hal/thread.h"
#include "hal/locker.h"
#include "hal/event.h"
#include "rplidar_driver_serial.h"

#ifndef min
#define min(a, b) (((a) < (b)) ? (a) : (b))
#endif

namespace rp
{
namespace standalone
{
namespace rplidar
{
// Factory Impl
RPlidarDriver* RPlidarDriver::CreateDriver(_u32 drivertype)
{
        switch (drivertype)
        {
                case DRIVER_TYPE_SERIALPORT:
                        return new RPlidarDriverSerialImpl();
                default:
                        return nullptr;
        }
}

void RPlidarDriver::DisposeDriver(RPlidarDriver* drv) { delete drv; }
// Serial Driver Impl

RPlidarDriverSerialImpl::RPlidarDriverSerialImpl()
        : _isConnected(false), _isScanning(false), _isSupportingMotorCtrl(false)
{
        _rxtx = rp::hal::serial_rxtx::CreateRxTx();
        _cached_scan_node_count = 0;
        _cached_sampleduration_std = LEGACY_SAMPLE_DURATION;
        _cached_sampleduration_express = LEGACY_SAMPLE_DURATION;
}

RPlidarDriverSerialImpl::~RPlidarDriverSerialImpl()
{
        // force disconnection
        disconnect();

        rp::hal::serial_rxtx::ReleaseRxTx(_rxtx);
}

u_result RPlidarDriverSerialImpl::connect(
        const char* port_path, _u32 baudrate, _u32 flag)
{
        if (isConnected()) return RESULT_ALREADY_DONE;

        if (!_rxtx) return RESULT_INSUFFICIENT_MEMORY;

        {
                rp::hal::AutoLocker l(_lock);

                // establish the serial connection...
                if (!_rxtx->bind(port_path, baudrate) || !_rxtx->open())
                {
                        return RESULT_INVALID_DATA;
                }

                _rxtx->flush(0);
        }

        _isConnected = true;

        checkMotorCtrlSupport(_isSupportingMotorCtrl);
        stopMotor();

        return RESULT_OK;
}

void RPlidarDriverSerialImpl::disconnect()
{
        if (!_isConnected) return;
        stop();
        _rxtx->close();
}

bool RPlidarDriverSerialImpl::isConnected() { return _isConnected; }
u_result RPlidarDriverSerialImpl::reset(_u32 timeout)
{
        u_result ans;

        {
                rp::hal::AutoLocker l(_lock);

                if (IS_FAIL(ans = _sendCommand(RPLIDAR_CMD_RESET)))
                {
                        return ans;
                }
        }
        return RESULT_OK;
}

u_result RPlidarDriverSerialImpl::getHealth(
        rplidar_response_device_health_t& healthinfo, _u32 timeout)
{
        u_result ans;

        if (!isConnected()) return RESULT_OPERATION_FAIL;

        _disableDataGrabbing();

        {
                rp::hal::AutoLocker l(_lock);

                if (IS_FAIL(ans = _sendCommand(RPLIDAR_CMD_GET_DEVICE_HEALTH)))
                {
                        return ans;
                }

                rplidar_ans_header_t response_header;
                if (IS_FAIL(ans = _waitResponseHeader(&response_header, timeout)))
                {
                        return ans;
                }

                // verify whether we got a correct header
                if (response_header.type != RPLIDAR_ANS_TYPE_DEVHEALTH)
                {
                        return RESULT_INVALID_DATA;
                }

                _u32 header_size =
                        (response_header.size_q30_subtype & RPLIDAR_ANS_HEADER_SIZE_MASK);
                if (header_size < sizeof(rplidar_response_device_health_t))
                {
                        return RESULT_INVALID_DATA;
                }

                if (_rxtx->waitfordata(header_size, timeout) !=
                        rp::hal::serial_rxtx::ANS_OK)
                {
                        return RESULT_OPERATION_TIMEOUT;
                }
                _rxtx->recvdata(
                        reinterpret_cast<_u8*>(&healthinfo), sizeof(healthinfo));
        }
        return RESULT_OK;
}

u_result RPlidarDriverSerialImpl::getDeviceInfo(
        rplidar_response_device_info_t& info, _u32 timeout)
{
        u_result ans;

        if (!isConnected()) return RESULT_OPERATION_FAIL;

        _disableDataGrabbing();

        {
                rp::hal::AutoLocker l(_lock);

                if (IS_FAIL(ans = _sendCommand(RPLIDAR_CMD_GET_DEVICE_INFO)))
                {
                        return ans;
                }

                rplidar_ans_header_t response_header;
                if (IS_FAIL(ans = _waitResponseHeader(&response_header, timeout)))
                {
                        return ans;
                }

                // verify whether we got a correct header
                if (response_header.type != RPLIDAR_ANS_TYPE_DEVINFO)
                {
                        return RESULT_INVALID_DATA;
                }

                _u32 header_size =
                        (response_header.size_q30_subtype & RPLIDAR_ANS_HEADER_SIZE_MASK);
                if (header_size < sizeof(rplidar_response_device_info_t))
                {
                        return RESULT_INVALID_DATA;
                }

                if (_rxtx->waitfordata(header_size, timeout) !=
                        rp::hal::serial_rxtx::ANS_OK)
                {
                        return RESULT_OPERATION_TIMEOUT;
                }

                _rxtx->recvdata(reinterpret_cast<_u8*>(&info), sizeof(info));
        }
        return RESULT_OK;
}

u_result RPlidarDriverSerialImpl::getFrequency(
        bool inExpressMode, size_t count, float& frequency, bool& is4kmode)
{
        _u16 sample_duration = inExpressMode ? _cached_sampleduration_express
                                                                                 : _cached_sampleduration_std;
        frequency = 1000000.0f / (count * sample_duration);

        if (sample_duration <= 277)
        {
                is4kmode = true;
        }
        else
        {
                is4kmode = false;
        }

        return RESULT_OK;
}

u_result RPlidarDriverSerialImpl::startScanNormal(bool force, _u32 timeout)
{
        u_result ans;
        if (!isConnected()) return RESULT_OPERATION_FAIL;
        if (_isScanning) return RESULT_ALREADY_DONE;

        stop();  // force the previous operation to stop

        {
                rp::hal::AutoLocker l(_lock);

                if (IS_FAIL(
                                ans = _sendCommand(
                                        force ? RPLIDAR_CMD_FORCE_SCAN : RPLIDAR_CMD_SCAN)))
                {
                        return ans;
                }

                // waiting for confirmation
                rplidar_ans_header_t response_header;
                if (IS_FAIL(ans = _waitResponseHeader(&response_header, timeout)))
                {
                        return ans;
                }

                // verify whether we got a correct header
                if (response_header.type != RPLIDAR_ANS_TYPE_MEASUREMENT)
                {
                        return RESULT_INVALID_DATA;
                }

                _u32 header_size =
                        (response_header.size_q30_subtype & RPLIDAR_ANS_HEADER_SIZE_MASK);
                if (header_size < sizeof(rplidar_response_measurement_node_t))
                {
                        return RESULT_INVALID_DATA;
                }

                _isScanning = true;
                _cachethread = CLASS_THREAD(RPlidarDriverSerialImpl, _cacheScanData);
                if (_cachethread.getHandle() == 0)
                {
                        return RESULT_OPERATION_FAIL;
                }
        }
        return RESULT_OK;
}

u_result RPlidarDriverSerialImpl::checkExpressScanSupported(
        bool& support, _u32 timeout)
{
        rplidar_response_device_info_t devinfo;

        support = false;
        u_result ans = getDeviceInfo(devinfo, timeout);

        if (IS_FAIL(ans)) return ans;

        if (devinfo.firmware_version >= ((0x1 << 8) | 17))
        {
                support = true;
                rplidar_response_sample_rate_t sample_rate;
                getSampleDuration_uS(sample_rate);
                _cached_sampleduration_express = sample_rate.express_sample_duration_us;
                _cached_sampleduration_std = sample_rate.std_sample_duration_us;
        }

        return RESULT_OK;
}

u_result RPlidarDriverSerialImpl::startScanExpress(
        bool fixedAngle, _u32 timeout)
{
        u_result ans;
        if (!isConnected()) return RESULT_OPERATION_FAIL;
        if (_isScanning) return RESULT_ALREADY_DONE;

        stop();  // force the previous operation to stop

        {
                rp::hal::AutoLocker l(_lock);

                rplidar_payload_express_scan_t scanReq;
                scanReq.working_mode =
                        (fixedAngle ? RPLIDAR_EXPRESS_SCAN_MODE_FIXANGLE
                                                : RPLIDAR_EXPRESS_SCAN_MODE_NORMAL);
                scanReq.reserved = 0;

                if (IS_FAIL(
                                ans = _sendCommand(
                                        RPLIDAR_CMD_EXPRESS_SCAN, &scanReq, sizeof(scanReq))))
                {
                        return ans;
                }

                // waiting for confirmation
                rplidar_ans_header_t response_header;
                if (IS_FAIL(ans = _waitResponseHeader(&response_header, timeout)))
                {
                        return ans;
                }

                // verify whether we got a correct header
                if (response_header.type != RPLIDAR_ANS_TYPE_MEASUREMENT_CAPSULED)
                {
                        return RESULT_INVALID_DATA;
                }

                _u32 header_size =
                        (response_header.size_q30_subtype & RPLIDAR_ANS_HEADER_SIZE_MASK);
                if (header_size < sizeof(rplidar_response_capsule_measurement_nodes_t))
                {
                        return RESULT_INVALID_DATA;
                }

                _isScanning = true;
                _cachethread =
                        CLASS_THREAD(RPlidarDriverSerialImpl, _cacheCapsuledScanData);
                if (_cachethread.getHandle() == 0)
                {
                        return RESULT_OPERATION_FAIL;
                }
        }
        return RESULT_OK;
}

u_result RPlidarDriverSerialImpl::startScan(bool force, bool autoExpressMode)
{
        bool isExpressModeSupported;
        u_result ans;

        if (autoExpressMode)
        {
                ans = checkExpressScanSupported(isExpressModeSupported);

                if (IS_FAIL(ans)) return ans;

                if (isExpressModeSupported)
                {
                        return startScanExpress(false);
                }
        }

        return startScanNormal(force);
}

u_result RPlidarDriverSerialImpl::stop(_u32 timeout)
{
        u_result ans;
        _disableDataGrabbing();

        {
                rp::hal::AutoLocker l(_lock);

                if (IS_FAIL(ans = _sendCommand(RPLIDAR_CMD_STOP)))
                {
                        return ans;
                }
        }

        return RESULT_OK;
}

u_result RPlidarDriverSerialImpl::_cacheScanData()
{
        rplidar_response_measurement_node_t local_buf[128];
        size_t count = 128;
        rplidar_response_measurement_node_t local_scan[MAX_SCAN_NODES];
        size_t scan_count = 0;
        u_result ans;
        memset(local_scan, 0, sizeof(local_scan));

        _waitScanData(
                local_buf,
                count);  // // always discard the first data since it may be incomplete

        while (_isScanning)
        {
                if (IS_FAIL(ans = _waitScanData(local_buf, count)))
                {
                        if (ans != RESULT_OPERATION_TIMEOUT)
                        {
                                _isScanning = false;
                                return RESULT_OPERATION_FAIL;
                        }
                }

                for (size_t pos = 0; pos < count; ++pos)
                {
                        if (local_buf[pos].sync_quality & RPLIDAR_RESP_MEASUREMENT_SYNCBIT)
                        {
                                // only publish the data when it contains a full 360 degree scan

                                if ((local_scan[0].sync_quality &
                                         RPLIDAR_RESP_MEASUREMENT_SYNCBIT))
                                {
                                        _lock.lock();
                                        memcpy(
                                                _cached_scan_node_buf, local_scan,
                                                scan_count *
                                                        sizeof(rplidar_response_measurement_node_t));
                                        _cached_scan_node_count = scan_count;
                                        _dataEvt.set();
                                        _lock.unlock();
                                }
                                scan_count = 0;
                        }
                        local_scan[scan_count++] = local_buf[pos];
                        if (scan_count == _countof(local_scan))
                                scan_count -= 1;  // prevent overflow
                }
        }
        _isScanning = false;
        return RESULT_OK;
}

void RPlidarDriverSerialImpl::_capsuleToNormal(
        const rplidar_response_capsule_measurement_nodes_t& capsule,
        rplidar_response_measurement_node_t* nodebuffer, size_t& nodeCount)
{
        nodeCount = 0;
        if (_is_previous_capsuledataRdy)
        {
                int diffAngle_q8;
                int currentStartAngle_q8 =
                        ((capsule.start_angle_sync_q6 & 0x7FFF) << 2);
                int prevStartAngle_q8 =
                        ((_cached_previous_capsuledata.start_angle_sync_q6 & 0x7FFF) << 2);

                diffAngle_q8 = (currentStartAngle_q8) - (prevStartAngle_q8);
                if (prevStartAngle_q8 > currentStartAngle_q8)
                {
                        diffAngle_q8 += (360 << 8);
                }

                int angleInc_q16 = (diffAngle_q8 << 3);
                int currentAngle_raw_q16 = (prevStartAngle_q8 << 8);
                for (size_t pos = 0;
                         pos < _countof(_cached_previous_capsuledata.cabins); ++pos)
                {
                        int dist_q2[2];
                        int angle_q6[2];
                        int syncBit[2];

                        dist_q2[0] =
                                (_cached_previous_capsuledata.cabins[pos].distance_angle_1 &
                                 0xFFFC);
                        dist_q2[1] =
                                (_cached_previous_capsuledata.cabins[pos].distance_angle_2 &
                                 0xFFFC);

                        int angle_offset1_q3 =
                                ((_cached_previous_capsuledata.cabins[pos].offset_angles_q3 &
                                  0xF) |
                                 ((_cached_previous_capsuledata.cabins[pos].distance_angle_1 &
                                   0x3)
                                  << 4));
                        int angle_offset2_q3 =
                                ((_cached_previous_capsuledata.cabins[pos].offset_angles_q3 >>
                                  4) |
                                 ((_cached_previous_capsuledata.cabins[pos].distance_angle_2 &
                                   0x3)
                                  << 4));

                        angle_q6[0] =
                                ((currentAngle_raw_q16 - (angle_offset1_q3 << 13)) >> 10);
                        syncBit[0] = (((currentAngle_raw_q16 + angleInc_q16) %
                                                   (360 << 16)) < angleInc_q16)
                                                         ? 1
                                                         : 0;
                        currentAngle_raw_q16 += angleInc_q16;

                        angle_q6[1] =
                                ((currentAngle_raw_q16 - (angle_offset2_q3 << 13)) >> 10);
                        syncBit[1] = (((currentAngle_raw_q16 + angleInc_q16) %
                                                   (360 << 16)) < angleInc_q16)
                                                         ? 1
                                                         : 0;
                        currentAngle_raw_q16 += angleInc_q16;

                        for (int cpos = 0; cpos < 2; ++cpos)
                        {
                                if (angle_q6[cpos] < 0) angle_q6[cpos] += (360 << 6);
                                if (angle_q6[cpos] >= (360 << 6)) angle_q6[cpos] -= (360 << 6);

                                rplidar_response_measurement_node_t node;

                                node.sync_quality = (syncBit[cpos] | ((!syncBit[cpos]) << 1));
                                if (dist_q2[cpos])
                                        node.sync_quality |=
                                                (0x2F << RPLIDAR_RESP_MEASUREMENT_QUALITY_SHIFT);

                                node.angle_q6_checkbit = (1 | (angle_q6[cpos] << 1));
                                node.distance_q2 = dist_q2[cpos];

                                nodebuffer[nodeCount++] = node;
                        }
                }
        }

        _cached_previous_capsuledata = capsule;
        _is_previous_capsuledataRdy = true;
}

u_result RPlidarDriverSerialImpl::_cacheCapsuledScanData()
{
        rplidar_response_capsule_measurement_nodes_t capsule_node;
        rplidar_response_measurement_node_t local_buf[128];
        size_t count = 128;
        rplidar_response_measurement_node_t local_scan[MAX_SCAN_NODES];
        size_t scan_count = 0;
        u_result ans;
        memset(local_scan, 0, sizeof(local_scan));

        _waitCapsuledNode(capsule_node);  // // always discard the first data since
        // it may be incomplete

        while (_isScanning)
        {
                if (IS_FAIL(ans = _waitCapsuledNode(capsule_node)))
                {
                        if (ans != RESULT_OPERATION_TIMEOUT && ans != RESULT_INVALID_DATA)
                        {
                                _isScanning = false;
                                return RESULT_OPERATION_FAIL;
                        }
                        else
                        {
                                // current data is invalid, do not use it.
                                continue;
                        }
                }

                _capsuleToNormal(capsule_node, local_buf, count);

                for (size_t pos = 0; pos < count; ++pos)
                {
                        if (local_buf[pos].sync_quality & RPLIDAR_RESP_MEASUREMENT_SYNCBIT)
                        {
                                // only publish the data when it contains a full 360 degree scan

                                if ((local_scan[0].sync_quality &
                                         RPLIDAR_RESP_MEASUREMENT_SYNCBIT))
                                {
                                        _lock.lock();
                                        memcpy(
                                                _cached_scan_node_buf, local_scan,
                                                scan_count *
                                                        sizeof(rplidar_response_measurement_node_t));
                                        _cached_scan_node_count = scan_count;
                                        _dataEvt.set();
                                        _lock.unlock();
                                }
                                scan_count = 0;
                        }
                        local_scan[scan_count++] = local_buf[pos];
                        if (scan_count == _countof(local_scan))
                                scan_count -= 1;  // prevent overflow
                }
        }
        _isScanning = false;

        return RESULT_OK;
}

u_result RPlidarDriverSerialImpl::grabScanData(
        rplidar_response_measurement_node_t* nodebuffer, size_t& count,
        _u32 timeout)
{
        switch (_dataEvt.wait(timeout))
        {
                case rp::hal::Event::EVENT_TIMEOUT:
                        count = 0;
                        return RESULT_OPERATION_TIMEOUT;
                case rp::hal::Event::EVENT_OK:
                {
                        if (_cached_scan_node_count == 0)
                                return RESULT_OPERATION_TIMEOUT;  // consider as timeout

                        rp::hal::AutoLocker l(_lock);

                        size_t size_to_copy = min(count, _cached_scan_node_count);

                        memcpy(
                                nodebuffer, _cached_scan_node_buf,
                                size_to_copy * sizeof(rplidar_response_measurement_node_t));
                        count = size_to_copy;
                        _cached_scan_node_count = 0;
                }
                        return RESULT_OK;

                default:
                        count = 0;
                        return RESULT_OPERATION_FAIL;
        }
}

u_result RPlidarDriverSerialImpl::ascendScanData(
        rplidar_response_measurement_node_t* nodebuffer, size_t count)
{
        float inc_origin_angle = 360.0f / count;
        size_t i = 0;

        // Tune head
        for (i = 0; i < count && nodebuffer[i].distance_q2 == 0; i++)
                ;

        // all the data is invalid
        if (i == count) return RESULT_OPERATION_FAIL;

        while (i != 0)
        {
                i--;
                float expect_angle = (nodebuffer[i + 1].angle_q6_checkbit >>
                                                          RPLIDAR_RESP_MEASUREMENT_ANGLE_SHIFT) /
                                                                 64.0f -
                                                         inc_origin_angle;
                if (expect_angle < 0.0f) expect_angle = 0.0f;
                _u16 checkbit =
                        nodebuffer[i].angle_q6_checkbit & RPLIDAR_RESP_MEASUREMENT_CHECKBIT;
                nodebuffer[i].angle_q6_checkbit =
                        (((_u16)(expect_angle * 64.0f))
                         << RPLIDAR_RESP_MEASUREMENT_ANGLE_SHIFT) +
                        checkbit;
        }

        // Tune tail
        for (i = count - 1; nodebuffer[i].distance_q2 == 0; i--)
                ;

        while (i != (count - 1))
        {
                i++;
                float expect_angle = (nodebuffer[i - 1].angle_q6_checkbit >>
                                                          RPLIDAR_RESP_MEASUREMENT_ANGLE_SHIFT) /
                                                                 64.0f +
                                                         inc_origin_angle;
                if (expect_angle > 360.0f) expect_angle -= 360.0f;
                _u16 checkbit =
                        nodebuffer[i].angle_q6_checkbit & RPLIDAR_RESP_MEASUREMENT_CHECKBIT;
                nodebuffer[i].angle_q6_checkbit =
                        (((_u16)(expect_angle * 64.0f))
                         << RPLIDAR_RESP_MEASUREMENT_ANGLE_SHIFT) +
                        checkbit;
        }

        // Fill invalid angle in the scan
        float frontAngle = (nodebuffer[0].angle_q6_checkbit >>
                                                RPLIDAR_RESP_MEASUREMENT_ANGLE_SHIFT) /
                                           64.0f;
        for (i = 1; i < count; i++)
        {
                if (nodebuffer[i].distance_q2 == 0)
                {
                        float expect_angle = frontAngle + i * inc_origin_angle;
                        if (expect_angle > 360.0f) expect_angle -= 360.0f;
                        _u16 checkbit = nodebuffer[i].angle_q6_checkbit &
                                                        RPLIDAR_RESP_MEASUREMENT_CHECKBIT;
                        nodebuffer[i].angle_q6_checkbit =
                                (((_u16)(expect_angle * 64.0f))
                                 << RPLIDAR_RESP_MEASUREMENT_ANGLE_SHIFT) +
                                checkbit;
                }
        }

        // Reorder the scan according to the angle value
        for (i = 0; i < (count - 1); i++)
        {
                for (size_t j = (i + 1); j < count; j++)
                {
                        if (nodebuffer[i].angle_q6_checkbit >
                                nodebuffer[j].angle_q6_checkbit)
                        {
                                rplidar_response_measurement_node_t temp = nodebuffer[i];
                                nodebuffer[i] = nodebuffer[j];
                                nodebuffer[j] = temp;
                        }
                }
        }

        return RESULT_OK;
}

u_result RPlidarDriverSerialImpl::_waitNode(
        rplidar_response_measurement_node_t* node, _u32 timeout)
{
        int recvPos = 0;
        _u32 startTs = getms();
        _u8 recvBuffer[sizeof(rplidar_response_measurement_node_t)];
        _u8* nodeBuffer = (_u8*)node;
        _u32 waitTime;

        while ((waitTime = getms() - startTs) <= timeout)
        {
                size_t remainSize =
                        sizeof(rplidar_response_measurement_node_t) - recvPos;
                size_t recvSize;

                int ans = _rxtx->waitfordata(remainSize, timeout - waitTime, &recvSize);
                if (ans == rp::hal::serial_rxtx::ANS_DEV_ERR)
                        return RESULT_OPERATION_FAIL;
                else if (ans == rp::hal::serial_rxtx::ANS_TIMEOUT)
                        return RESULT_OPERATION_TIMEOUT;

                if (recvSize > remainSize) recvSize = remainSize;

                _rxtx->recvdata(recvBuffer, recvSize);

                for (size_t pos = 0; pos < recvSize; ++pos)
                {
                        _u8 currentByte = recvBuffer[pos];
                        switch (recvPos)
                        {
                                case 0:  // expect the sync bit and its reverse in this byte
                                {
                                        _u8 tmp = (currentByte >> 1);
                                        if ((tmp ^ currentByte) & 0x1)
                                        {
                                                // pass
                                        }
                                        else
                                        {
                                                continue;
                                        }
                                }
                                break;
                                case 1:  // expect the highest bit to be 1
                                {
                                        if (currentByte & RPLIDAR_RESP_MEASUREMENT_CHECKBIT)
                                        {
                                                // pass
                                        }
                                        else
                                        {
                                                recvPos = 0;
                                                continue;
                                        }
                                }
                                break;
                        }
                        nodeBuffer[recvPos++] = currentByte;

                        if (recvPos == sizeof(rplidar_response_measurement_node_t))
                        {
                                return RESULT_OK;
                        }
                }
        }

        return RESULT_OPERATION_TIMEOUT;
}

u_result RPlidarDriverSerialImpl::_waitScanData(
        rplidar_response_measurement_node_t* nodebuffer, size_t& count,
        _u32 timeout)
{
        if (!_isConnected)
        {
                count = 0;
                return RESULT_OPERATION_FAIL;
        }

        size_t recvNodeCount = 0;
        _u32 startTs = getms();
        _u32 waitTime;
        u_result ans;

        while ((waitTime = getms() - startTs) <= timeout && recvNodeCount < count)
        {
                rplidar_response_measurement_node_t node;
                if (IS_FAIL(ans = _waitNode(&node, timeout - waitTime)))
                {
                        return ans;
                }

                nodebuffer[recvNodeCount++] = node;

                if (recvNodeCount == count) return RESULT_OK;
        }
        count = recvNodeCount;
        return RESULT_OPERATION_TIMEOUT;
}

u_result RPlidarDriverSerialImpl::_waitCapsuledNode(
        rplidar_response_capsule_measurement_nodes_t& node, _u32 timeout)
{
        int recvPos = 0;
        _u32 startTs = getms();
        _u8 recvBuffer[sizeof(rplidar_response_capsule_measurement_nodes_t)];
        _u8* nodeBuffer = (_u8*)&node;
        _u32 waitTime;

        while ((waitTime = getms() - startTs) <= timeout)
        {
                size_t remainSize =
                        sizeof(rplidar_response_capsule_measurement_nodes_t) - recvPos;
                size_t recvSize;

                int ans = _rxtx->waitfordata(remainSize, timeout - waitTime, &recvSize);
                if (ans == rp::hal::serial_rxtx::ANS_DEV_ERR)
                        return RESULT_OPERATION_FAIL;
                else if (ans == rp::hal::serial_rxtx::ANS_TIMEOUT)
                        return RESULT_OPERATION_TIMEOUT;

                if (recvSize > remainSize) recvSize = remainSize;

                _rxtx->recvdata(recvBuffer, recvSize);

                for (size_t pos = 0; pos < recvSize; ++pos)
                {
                        _u8 currentByte = recvBuffer[pos];
                        switch (recvPos)
                        {
                                case 0:  // expect the sync bit 1
                                {
                                        _u8 tmp = (currentByte >> 4);
                                        if (tmp == RPLIDAR_RESP_MEASUREMENT_EXP_SYNC_1)
                                        {
                                                // pass
                                        }
                                        else
                                        {
                                                _is_previous_capsuledataRdy = false;
                                                continue;
                                        }
                                }
                                break;
                                case 1:  // expect the sync bit 2
                                {
                                        _u8 tmp = (currentByte >> 4);
                                        if (tmp == RPLIDAR_RESP_MEASUREMENT_EXP_SYNC_2)
                                        {
                                                // pass
                                        }
                                        else
                                        {
                                                recvPos = 0;
                                                _is_previous_capsuledataRdy = false;
                                                continue;
                                        }
                                }
                                break;
                        }
                        nodeBuffer[recvPos++] = currentByte;

                        if (recvPos == sizeof(rplidar_response_capsule_measurement_nodes_t))
                        {
                                // calc the checksum ...
                                _u8 checksum = 0;
                                _u8 recvChecksum =
                                        ((node.s_checksum_1 & 0xF) | (node.s_checksum_2 << 4));
                                for (size_t cpos = offsetof(
                                                 rplidar_response_capsule_measurement_nodes_t,
                                                 start_angle_sync_q6);
                                         cpos <
                                         sizeof(rplidar_response_capsule_measurement_nodes_t);
                                         ++cpos)
                                {
                                        checksum ^= nodeBuffer[cpos];
                                }
                                if (recvChecksum == checksum)
                                {
                                        // only consider vaild if the checksum matches...
                                        if (node.start_angle_sync_q6 &
                                                RPLIDAR_RESP_MEASUREMENT_EXP_SYNCBIT)
                                        {
                                                // this is the first capsule frame in logic, discard the
                                                // previous cached data...
                                                _is_previous_capsuledataRdy = false;
                                                return RESULT_OK;
                                        }
                                        return RESULT_OK;
                                }
                                _is_previous_capsuledataRdy = false;
                                return RESULT_INVALID_DATA;
                        }
                }
        }
        _is_previous_capsuledataRdy = false;
        return RESULT_OPERATION_TIMEOUT;
}

u_result RPlidarDriverSerialImpl::_sendCommand(
        _u8 cmd, const void* payload, size_t payloadsize)
{
        _u8 pkt_header[10];
        rplidar_cmd_packet_t* header =
                reinterpret_cast<rplidar_cmd_packet_t*>(pkt_header);
        _u8 checksum = 0;

        if (!_isConnected) return RESULT_OPERATION_FAIL;

        if (payloadsize && payload)
        {
                cmd |= RPLIDAR_CMDFLAG_HAS_PAYLOAD;
        }

        header->syncByte = RPLIDAR_CMD_SYNC_BYTE;
        header->cmd_flag = cmd;

        // send header first
        _rxtx->senddata(pkt_header, 2);

        if (cmd & RPLIDAR_CMDFLAG_HAS_PAYLOAD)
        {
                checksum ^= RPLIDAR_CMD_SYNC_BYTE;
                checksum ^= cmd;
                checksum ^= (payloadsize & 0xFF);

                // calc checksum
                for (size_t pos = 0; pos < payloadsize; ++pos)
                {
                        checksum ^= ((_u8*)payload)[pos];
                }

                // send size
                _u8 sizebyte = payloadsize;
                _rxtx->senddata(&sizebyte, 1);

                // send payload
                _rxtx->senddata((const _u8*)payload, sizebyte);

                // send checksum
                _rxtx->senddata(&checksum, 1);
        }

        return RESULT_OK;
}

u_result RPlidarDriverSerialImpl::_waitResponseHeader(
        rplidar_ans_header_t* header, _u32 timeout)
{
        int recvPos = 0;
        _u32 startTs = getms();
        _u8 recvBuffer[sizeof(rplidar_ans_header_t)];
        _u8* headerBuffer = reinterpret_cast<_u8*>(header);
        _u32 waitTime;

        while ((waitTime = getms() - startTs) <= timeout)
        {
                size_t remainSize = sizeof(rplidar_ans_header_t) - recvPos;
                size_t recvSize;

                int ans = _rxtx->waitfordata(remainSize, timeout - waitTime, &recvSize);
                if (ans == rp::hal::serial_rxtx::ANS_DEV_ERR)
                        return RESULT_OPERATION_FAIL;
                else if (ans == rp::hal::serial_rxtx::ANS_TIMEOUT)
                        return RESULT_OPERATION_TIMEOUT;

                if (recvSize > remainSize) recvSize = remainSize;

                _rxtx->recvdata(recvBuffer, recvSize);

                for (size_t pos = 0; pos < recvSize; ++pos)
                {
                        _u8 currentByte = recvBuffer[pos];
                        switch (recvPos)
                        {
                                case 0:
                                        if (currentByte != RPLIDAR_ANS_SYNC_BYTE1)
                                        {
                                                continue;
                                        }

                                        break;
                                case 1:
                                        if (currentByte != RPLIDAR_ANS_SYNC_BYTE2)
                                        {
                                                recvPos = 0;
                                                continue;
                                        }
                                        break;
                        }
                        headerBuffer[recvPos++] = currentByte;

                        if (recvPos == sizeof(rplidar_ans_header_t))
                        {
                                return RESULT_OK;
                        }
                }
        }

        return RESULT_OPERATION_TIMEOUT;
}

void RPlidarDriverSerialImpl::_disableDataGrabbing()
{
        _isScanning = false;
        _cachethread.join();
}

u_result RPlidarDriverSerialImpl::getSampleDuration_uS(
        rplidar_response_sample_rate_t& rateInfo, _u32 timeout)
{
        if (!isConnected()) return RESULT_OPERATION_FAIL;

        _disableDataGrabbing();

        rplidar_response_device_info_t devinfo;
        // 1. fetch the device version first...
        u_result ans = getDeviceInfo(devinfo, timeout);

        rateInfo.express_sample_duration_us = _cached_sampleduration_express;
        rateInfo.std_sample_duration_us = _cached_sampleduration_std;

        if (devinfo.firmware_version < ((0x1 << 8) | 17))
        {
                // provide fake data...

                return RESULT_OK;
        }

        {
                rp::hal::AutoLocker l(_lock);

                if (IS_FAIL(ans = _sendCommand(RPLIDAR_CMD_GET_SAMPLERATE)))
                {
                        return ans;
                }

                rplidar_ans_header_t response_header;
                if (IS_FAIL(ans = _waitResponseHeader(&response_header, timeout)))
                {
                        return ans;
                }

                // verify whether we got a correct header
                if (response_header.type != RPLIDAR_ANS_TYPE_SAMPLE_RATE)
                {
                        return RESULT_INVALID_DATA;
                }

                _u32 header_size =
                        (response_header.size_q30_subtype & RPLIDAR_ANS_HEADER_SIZE_MASK);
                if (header_size < sizeof(rplidar_response_sample_rate_t))
                {
                        return RESULT_INVALID_DATA;
                }

                if (_rxtx->waitfordata(header_size, timeout) !=
                        rp::hal::serial_rxtx::ANS_OK)
                {
                        return RESULT_OPERATION_TIMEOUT;
                }
                _rxtx->recvdata(reinterpret_cast<_u8*>(&rateInfo), sizeof(rateInfo));
        }
        return RESULT_OK;
}

u_result RPlidarDriverSerialImpl::checkMotorCtrlSupport(
        bool& support, _u32 timeout)
{
        u_result ans;
        support = false;

        if (!isConnected()) return RESULT_OPERATION_FAIL;

        _disableDataGrabbing();

        {
                rp::hal::AutoLocker l(_lock);

                rplidar_payload_acc_board_flag_t flag;
                flag.reserved = 0;

                if (IS_FAIL(
                                ans = _sendCommand(
                                        RPLIDAR_CMD_GET_ACC_BOARD_FLAG, &flag, sizeof(flag))))
                {
                        return ans;
                }

                rplidar_ans_header_t response_header;
                if (IS_FAIL(ans = _waitResponseHeader(&response_header, timeout)))
                {
                        return ans;
                }

                // verify whether we got a correct header
                if (response_header.type != RPLIDAR_ANS_TYPE_ACC_BOARD_FLAG)
                {
                        return RESULT_INVALID_DATA;
                }

                _u32 header_size =
                        (response_header.size_q30_subtype & RPLIDAR_ANS_HEADER_SIZE_MASK);
                if (header_size < sizeof(rplidar_response_acc_board_flag_t))
                {
                        return RESULT_INVALID_DATA;
                }

                if (_rxtx->waitfordata(header_size, timeout) !=
                        rp::hal::serial_rxtx::ANS_OK)
                {
                        return RESULT_OPERATION_TIMEOUT;
                }
                rplidar_response_acc_board_flag_t acc_board_flag;
                _rxtx->recvdata(
                        reinterpret_cast<_u8*>(&acc_board_flag), sizeof(acc_board_flag));

                if (acc_board_flag.support_flag &
                        RPLIDAR_RESP_ACC_BOARD_FLAG_MOTOR_CTRL_SUPPORT_MASK)
                {
                        support = true;
                }
        }
        return RESULT_OK;
}

u_result RPlidarDriverSerialImpl::setMotorPWM(_u16 pwm)
{
        u_result ans;
        rplidar_payload_motor_pwm_t motor_pwm;
        motor_pwm.pwm_value = pwm;

        {
                rp::hal::AutoLocker l(_lock);

                if (IS_FAIL(
                                ans = _sendCommand(
                                        RPLIDAR_CMD_SET_MOTOR_PWM, (const _u8*)&motor_pwm,
                                        sizeof(motor_pwm))))
                {
                        return ans;
                }
        }

        return RESULT_OK;
}

u_result RPlidarDriverSerialImpl::startMotor()
{
        if (_isSupportingMotorCtrl)
        {  // RPLIDAR A2
                setMotorPWM(DEFAULT_MOTOR_PWM);
                delay(500);
                return RESULT_OK;
        }
        else
        {  // RPLIDAR A1
                rp::hal::AutoLocker l(_lock);
                _rxtx->clearDTR();
                delay(500);
                return RESULT_OK;
        }
}

u_result RPlidarDriverSerialImpl::stopMotor()
{
        if (_isSupportingMotorCtrl)
        {  // RPLIDAR A2
                setMotorPWM(0);
                delay(500);
                return RESULT_OK;
        }
        else
        {  // RPLIDAR A1
                rp::hal::AutoLocker l(_lock);
                _rxtx->setDTR();
                delay(500);
                return RESULT_OK;
        }
}
}
}
}