telemetry.cpp

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/****************************************************************************
 *
 *   Copyright (c) 2019 PX4 Development Team. All rights reserved.
 *
 * 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.
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 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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#include "telemetry.h"

#include <px4_platform_common/log.h>

#include <unistd.h>
#include <fcntl.h>
#include <termios.h>
#include <errno.h>

using namespace time_literals;

#define DSHOT_TELEMETRY_UART_BAUDRATE 115200

DShotTelemetry::~DShotTelemetry()
{
    deinit();
}

int DShotTelemetry::init(const char *uart_device)
{
    deinit();
    _uart_fd = ::open(uart_device, O_RDONLY | O_NOCTTY);

    if (_uart_fd < 0) {
        PX4_ERR("failed to open serial port: %s err: %d", uart_device, errno);
        return -errno;
    }

    _num_timeouts = 0;
    _num_successful_responses = 0;
    _current_motor_index_request = -1;
    return setBaudrate(DSHOT_TELEMETRY_UART_BAUDRATE);
}

void DShotTelemetry::deinit()
{
    if (_uart_fd >= 0) {
        close(_uart_fd);
        _uart_fd = -1;
    }
}

int DShotTelemetry::redirectOutput(OutputBuffer &buffer)
{
    if (expectingData()) {
        // Error: cannot override while we already expect data
        return -EBUSY;
    }

    _current_motor_index_request = buffer.motor_index;
    _current_request_start = hrt_absolute_time();
    _redirect_output = &buffer;
    _redirect_output->buf_pos = 0;
    return 0;
}

int DShotTelemetry::update()
{
    if (_uart_fd < 0) {
        return -1;
    }

    if (_current_motor_index_request == -1) {
        // nothing in progress, start a request
        _current_motor_index_request = 0;
        _current_request_start = 0;
        _frame_position = 0;
        return -1;
    }

    // read from the uart. This must be non-blocking, so check first if there is data available
    int bytes_available = 0;
    int ret = ioctl(_uart_fd, FIONREAD, (unsigned long)&bytes_available);

    if (ret != 0 || bytes_available <= 0) {
        // no data available. Check for a timeout
        const hrt_abstime now = hrt_absolute_time();

        if (_current_request_start > 0 && now - _current_request_start > 30_ms) {
            if (_redirect_output) {
                // clear and go back to internal buffer
                _redirect_output = nullptr;
                _current_motor_index_request = -1;

            } else {
                PX4_DEBUG("ESC telemetry timeout for motor %i (frame pos=%i)", _current_motor_index_request, _frame_position);
                ++_num_timeouts;
            }

            requestNextMotor();
            return -2;
        }

        return -1;
    }

    const int buf_length = ESC_FRAME_SIZE;
    uint8_t buf[buf_length];

    int num_read = read(_uart_fd, buf, buf_length);
    ret = -1;

    for (int i = 0; i < num_read && ret == -1; ++i) {
        if (_redirect_output) {
            _redirect_output->buffer[_redirect_output->buf_pos++] = buf[i];

            if (_redirect_output->buf_pos == sizeof(_redirect_output->buffer)) {
                // buffer full: return & go back to internal buffer
                _redirect_output = nullptr;
                ret = _current_motor_index_request;
                _current_motor_index_request = -1;
                requestNextMotor();
            }

        } else {
            bool successful_decoding;

            if (decodeByte(buf[i], successful_decoding)) {
                if (successful_decoding) {
                    ret = _current_motor_index_request;
                }

                requestNextMotor();
            }
        }
    }

    return ret;
}

bool DShotTelemetry::decodeByte(uint8_t byte, bool &successful_decoding)
{
    _frame_buffer[_frame_position++] = byte;
    successful_decoding = false;

    if (_frame_position == ESC_FRAME_SIZE) {
        PX4_DEBUG("got ESC frame for motor %i", _current_motor_index_request);
        uint8_t checksum = crc8(_frame_buffer, ESC_FRAME_SIZE - 1);
        uint8_t checksum_data = _frame_buffer[ESC_FRAME_SIZE - 1];

        if (checksum == checksum_data) {
            _latest_data.time = hrt_absolute_time();
            _latest_data.temperature = _frame_buffer[0];
            _latest_data.voltage = (_frame_buffer[1] << 8) | _frame_buffer[2];
            _latest_data.current = (_frame_buffer[3] << 8) | _frame_buffer[4];
            _latest_data.consumption = (_frame_buffer[5]) << 8 | _frame_buffer[6];
            _latest_data.erpm = (_frame_buffer[7] << 8) | _frame_buffer[8];
            PX4_DEBUG("Motor %i: temp=%i, V=%i, cur=%i, consumpt=%i, rpm=%i", _current_motor_index_request,
                  _latest_data.temperature, _latest_data.voltage, _latest_data.current, _latest_data.consumption,
                  _latest_data.erpm);
            ++_num_successful_responses;
            successful_decoding = true;
        }

        return true;
    }

    return false;
}

void DShotTelemetry::printStatus() const
{
    PX4_INFO("Number of successful ESC frames: %i", _num_successful_responses);
    PX4_INFO("Number of timeouts: %i", _num_timeouts);
}

uint8_t DShotTelemetry::updateCrc8(uint8_t crc, uint8_t crc_seed)
{
    uint8_t crc_u = crc ^ crc_seed;

    for (int i = 0; i < 8; ++i) {
        crc_u = (crc_u & 0x80) ? 0x7 ^ (crc_u << 1) : (crc_u << 1);
    }

    return crc_u;
}


uint8_t DShotTelemetry::crc8(const uint8_t *buf, uint8_t len)
{
    uint8_t crc = 0;

    for (int i = 0; i < len; ++i) {
        crc = updateCrc8(buf[i], crc);
    }

    return crc;
}


void DShotTelemetry::requestNextMotor()
{
    _current_motor_index_request = (_current_motor_index_request + 1) % _num_motors;
    _current_request_start = 0;
    _frame_position = 0;
}

int DShotTelemetry::getRequestMotorIndex()
{
    if (_current_request_start != 0) {
        // already in progress, do not send another request
        return -1;
    }

    _current_request_start = hrt_absolute_time();
    return _current_motor_index_request;
}

void DShotTelemetry::decodeAndPrintEscInfoPacket(const OutputBuffer &buffer)
{
    static constexpr int version_position = 12;
    const uint8_t *data = buffer.buffer;

    if (buffer.buf_pos < version_position) {
        PX4_ERR("Not enough data received");
        return;
    }

    enum class ESCVersionInfo {
        BLHELI32,
        KissV1,
        KissV2,
    };
    ESCVersionInfo version;
    int packet_length;

    if (data[version_position] == 254) {
        version = ESCVersionInfo::BLHELI32;
        packet_length = esc_info_size_blheli32;

    } else if (data[version_position] == 255) {
        version = ESCVersionInfo::KissV2;
        packet_length = esc_info_size_kiss_v2;

    } else {
        version = ESCVersionInfo::KissV1;
        packet_length = esc_info_size_kiss_v1;
    }

    if (buffer.buf_pos != packet_length) {
        PX4_ERR("Packet length mismatch (%i != %i)", buffer.buf_pos, packet_length);
        return;
    }

    if (DShotTelemetry::crc8(data, packet_length - 1) != data[packet_length - 1]) {
        PX4_ERR("Checksum mismatch");
        return;
    }

    uint8_t esc_firmware_version = 0;
    uint8_t esc_firmware_subversion = 0;
    uint8_t esc_type = 0;

    switch (version) {
    case ESCVersionInfo::KissV1:
        esc_firmware_version = data[12];
        esc_firmware_subversion = (data[13] & 0x1f) + 97;
        esc_type = (data[13] & 0xe0) >> 5;
        break;

    case ESCVersionInfo::KissV2:
    case ESCVersionInfo::BLHELI32:
        esc_firmware_version = data[13];
        esc_firmware_subversion = data[14];
        esc_type = data[15];
        break;
    }

    const char *esc_type_str = "";

    switch (version) {
    case ESCVersionInfo::KissV1:
    case ESCVersionInfo::KissV2:
        switch (esc_type) {
        case 1: esc_type_str = "KISS8A";
            break;

        case 2: esc_type_str = "KISS16A";
            break;

        case 3: esc_type_str = "KISS24A";
            break;

        case 5: esc_type_str = "KISS Ultralite";
            break;

        default: esc_type_str = "KISS (unknown)";
            break;
        }

        break;

    case ESCVersionInfo::BLHELI32: {
            char *esc_type_mutable = (char *)(data + 31);
            esc_type_mutable[32] = 0;
            esc_type_str = esc_type_mutable;
        }
        break;
    }

    PX4_INFO("ESC Type: %s", esc_type_str);

    PX4_INFO("MCU Serial Number: %02x%02x%02x-%02x%02x%02x-%02x%02x%02x-%02x%02x%02x",
         data[0], data[1], data[2], data[3], data[4], data[5], data[6], data[7], data[8],
         data[9], data[10], data[11]);

    switch (version) {
    case ESCVersionInfo::KissV1:
    case ESCVersionInfo::KissV2:
        PX4_INFO("Firmware version: %d.%d%c", esc_firmware_version / 100, esc_firmware_version % 100,
             (char)esc_firmware_subversion);
        break;

    case ESCVersionInfo::BLHELI32:
        PX4_INFO("Firmware version: %d.%d", esc_firmware_version, esc_firmware_subversion);
        break;
    }

    if (version == ESCVersionInfo::KissV2 || version == ESCVersionInfo::BLHELI32) {
        PX4_INFO("Rotation Direction: %s", data[16] ? "reversed" : "normal");
        PX4_INFO("3D Mode: %s", data[17] ? "on" : "off");
    }

    if (version == ESCVersionInfo::BLHELI32) {
        uint8_t setting = data[18];

        switch (setting) {
        case 0:
            PX4_INFO("Low voltage Limit: off");
            break;

        case 255:
            PX4_INFO("Low voltage Limit: unsupported");
            break;

        default:
            PX4_INFO("Low voltage Limit: %d.%01d V", setting / 10, setting % 10);
            break;
        }

        setting = data[19];

        switch (setting) {
        case 0:
            PX4_INFO("Current Limit: off");
            break;

        case 255:
            PX4_INFO("Current Limit: unsupported");
            break;

        default:
            PX4_INFO("Current Limit: %d A", setting);
            break;
        }

        for (int i = 0; i < 4; ++i) {
            setting = data[i + 20];
            PX4_INFO("LED %d: %s", i, setting ? (setting == 255 ? "unsupported" : "on") : "off");
        }
    }


}

int DShotTelemetry::setBaudrate(unsigned baud)
{
    int speed;

    switch (baud) {
    case 9600:   speed = B9600;   break;

    case 19200:  speed = B19200;  break;

    case 38400:  speed = B38400;  break;

    case 57600:  speed = B57600;  break;

    case 115200: speed = B115200; break;

    case 230400: speed = B230400; break;

    default:
        return -EINVAL;
    }

    struct termios uart_config;

    int termios_state;

    /* fill the struct for the new configuration */
    tcgetattr(_uart_fd, &uart_config);

    //
    // Input flags - Turn off input processing
    //
    // convert break to null byte, no CR to NL translation,
    // no NL to CR translation, don't mark parity errors or breaks
    // no input parity check, don't strip high bit off,
    // no XON/XOFF software flow control
    //
    uart_config.c_iflag &= ~(IGNBRK | BRKINT | ICRNL |
                 INLCR | PARMRK | INPCK | ISTRIP | IXON);
    //
    // Output flags - Turn off output processing
    //
    // no CR to NL translation, no NL to CR-NL translation,
    // no NL to CR translation, no column 0 CR suppression,
    // no Ctrl-D suppression, no fill characters, no case mapping,
    // no local output processing
    //
    // config.c_oflag &= ~(OCRNL | ONLCR | ONLRET |
    //                     ONOCR | ONOEOT| OFILL | OLCUC | OPOST);
    uart_config.c_oflag = 0;

    //
    // No line processing
    //
    // echo off, echo newline off, canonical mode off,
    // extended input processing off, signal chars off
    //
    uart_config.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN | ISIG);

    /* no parity, one stop bit, disable flow control */
    uart_config.c_cflag &= ~(CSTOPB | PARENB | CRTSCTS);

    /* set baud rate */
    if ((termios_state = cfsetispeed(&uart_config, speed)) < 0) {
        return -errno;
    }

    if ((termios_state = cfsetospeed(&uart_config, speed)) < 0) {
        return -errno;
    }

    if ((termios_state = tcsetattr(_uart_fd, TCSANOW, &uart_config)) < 0) {
        return -errno;
    }

    return 0;
}