Function parse

app/rcc/scripts/parser/js/modbus.js:165–308

* Parses a Modbus response frame into an array of values. * * @param {Uint8Array|Array} frame - Binary Modbus ADU (no CRC) * @returns {Array} Parsed values array for Serial Studio * * Frame Structure: * Byte 0: Slave/Unit address (1-247) * Byte 1: Function code (1-127) or Exception (1

(frame)

 *   Byte 2+:  Data payload (varies by function)
 */
function parse(frame) {
  frameCount++;

  if (!frame || frame.length < 3) {
    debugLog("Frame too short: " + (frame ? frame.length : 0) + " bytes");
    return parsedValues;
  }

  var slaveAddress = frame[0];
  var functionCode = frame[1];

  debugLog("Frame #" + frameCount + ": Slave=" + slaveAddress +
           " FC=0x" + functionCode.toString(16) + " Len=" + frame.length);

  //----------------------------------------------------------------------------
  // Exception Response (FC >= 0x80)
  //----------------------------------------------------------------------------
  if (functionCode >= 0x80) {
    var originalFC  = functionCode & 0x7F;
    var exceptionCode = frame[2];
    var exception   = MODBUS_EXCEPTIONS[exceptionCode] || { name: "UNKNOWN", desc: "Unknown exception" };

    lastException = {
      functionCode:  originalFC,
      exceptionCode: exceptionCode,
      name:          exception.name,
      description:   exception.desc,
      timestamp:     Date.now()
    };

    console.log("[Modbus Exception] FC=0x" + originalFC.toString(16) +
                " Error=0x" + exceptionCode.toString(16) +
                " (" + exception.name + ": " + exception.desc + ")");

    return parsedValues;
  }

  //----------------------------------------------------------------------------
  // Read Coils (0x01) / Read Discrete Inputs (0x02)
  //----------------------------------------------------------------------------
  if (functionCode === 0x01 || functionCode === 0x02) {
    var byteCount = frame[2];
    var bitIndex = 0;

    debugLog("Reading " + (byteCount * 8) + " bits");

    for (var byteIdx = 0; byteIdx < byteCount && bitIndex < CONFIG.numItems; byteIdx++) {
      var dataByte = frame[3 + byteIdx];
      for (var bit = 0; bit < 8 && bitIndex < CONFIG.numItems; bit++)
        parsedValues[bitIndex++] = (dataByte >> bit) & 0x01;
    }
  }

  //----------------------------------------------------------------------------
  // Read Holding Registers (0x03) / Read Input Registers (0x04)
  //----------------------------------------------------------------------------
  else if (functionCode === 0x03 || functionCode === 0x04) {
    var byteCount = frame[2];