modbus-connect/function-codes/read-device-identification.js

Modbus RTU over Web Serial and Node.js SerialPort

// function-codes/read-device-identification.js

const { sliceUint8Array, fromBytes } = require('../utils/utils.js');
const { FUNCTION_CODES } = require('../constants/constants.js');

const FUNCTION_CODE = FUNCTION_CODES.READ_DEVICE_IDENTIFICATION;
const MEI_TYPE = 0x0E;

function buildReadDeviceIdentificationRequest(categoryId = 0x01, objectId = 0x00) {
    return fromBytes(
        FUNCTION_CODE,
        MEI_TYPE,
        categoryId,
        objectId
    );
}

/**
 * Разбирает ответ функции 0x2B/0x0E (чтение идентификатора устройства).
 * @param {Uint8Array} response
 * @returns {{
 *   functionCode: number,
 *   meiType: number,
 *   category: number,
 *   conformityLevel: number,
 *   moreFollows: number,
 *   nextObjectId: number,
 *   numberOfObjects: number,
 *   objects: Record<number, string>
 * }}
 */
function parseReadDeviceIdentificationResponse(response) {
    if (response.length < 7) {
        throw new Error('Invalid Device Identification response length');
    }

    const functionCode = response[0];
    const meiType = response[1];
    const category = response[2];
    const conformityLevel = response[3];
    const moreFollows = response[4];
    const nextObjectId = response[5];
    const numberOfObjects = response[6];

    let offset = 7;
    const objects = {};

    // Используем windows-1251 для декодирования текста
    const decoder = new TextDecoder('windows-1251');

    for (let i = 0; i < numberOfObjects; i++) {
        const objectId = response[offset];
        const length = response[offset + 1];
        const stringBytes = sliceUint8Array(response, offset + 2, offset + 2 + length);
        const value = decoder.decode(stringBytes);
        objects[objectId] = value;
        offset += 2 + length;
    }

    return {
        functionCode,
        meiType,
        category,
        conformityLevel,
        moreFollows,
        nextObjectId,
        numberOfObjects,
        objects
    };
}

module.exports = {
    buildReadDeviceIdentificationRequest,
    parseReadDeviceIdentificationResponse
}