CRC16 Modbus implemented

CRC16_0x18005.js

@@ -0,0 +1,98 @@
+// Implements the CRC16 algorithm for MODBUS polynomial (0x18005)
+//
+//-----------------------------------------------------------------------
+// Date        Author      Change
+//-----------------------------------------------------------------------
+// 07.06.2020  D.Steidl    Created
+//-----------------------------------------------------------------------
+
+//-----------------------------------------------------------------------
+// Global variables
+//-----------------------------------------------------------------------
+
+// variables have to be declared explicitly
+'use strict'
+
+/** @const {Object} aCRCTable             Table for 8-bit fast calculation */
+const aCRCTable   = 
+[  0x0000, 0x8005, 0x800F, 0x000A, 0x801B, 0x001E, 0x0014, 0x8011, 0x8033, 0x0036, 0x003C, 0x8039, 0x0028, 0x802D, 0x8027, 0x0022,
+   0x8063, 0x0066, 0x006C, 0x8069, 0x0078, 0x807D, 0x8077, 0x0072, 0x0050, 0x8055, 0x805F, 0x005A, 0x804B, 0x004E, 0x0044, 0x8041,
+   0x80C3, 0x00C6, 0x00CC, 0x80C9, 0x00D8, 0x80DD, 0x80D7, 0x00D2, 0x00F0, 0x80F5, 0x80FF, 0x00FA, 0x80EB, 0x00EE, 0x00E4, 0x80E1,
+   0x00A0, 0x80A5, 0x80AF, 0x00AA, 0x80BB, 0x00BE, 0x00B4, 0x80B1, 0x8093, 0x0096, 0x009C, 0x8099, 0x0088, 0x808D, 0x8087, 0x0082,
+   0x8183, 0x0186, 0x018C, 0x8189, 0x0198, 0x819D, 0x8197, 0x0192, 0x01B0, 0x81B5, 0x81BF, 0x01BA, 0x81AB, 0x01AE, 0x01A4, 0x81A1,
+   0x01E0, 0x81E5, 0x81EF, 0x01EA, 0x81FB, 0x01FE, 0x01F4, 0x81F1, 0x81D3, 0x01D6, 0x01DC, 0x81D9, 0x01C8, 0x81CD, 0x81C7, 0x01C2,
+   0x0140, 0x8145, 0x814F, 0x014A, 0x815B, 0x015E, 0x0154, 0x8151, 0x8173, 0x0176, 0x017C, 0x8179, 0x0168, 0x816D, 0x8167, 0x0162,
+   0x8123, 0x0126, 0x012C, 0x8129, 0x0138, 0x813D, 0x8137, 0x0132, 0x0110, 0x8115, 0x811F, 0x011A, 0x810B, 0x010E, 0x0104, 0x8101,
+   0x8303, 0x0306, 0x030C, 0x8309, 0x0318, 0x831D, 0x8317, 0x0312, 0x0330, 0x8335, 0x833F, 0x033A, 0x832B, 0x032E, 0x0324, 0x8321,
+   0x0360, 0x8365, 0x836F, 0x036A, 0x837B, 0x037E, 0x0374, 0x8371, 0x8353, 0x0356, 0x035C, 0x8359, 0x0348, 0x834D, 0x8347, 0x0342,
+   0x03C0, 0x83C5, 0x83CF, 0x03CA, 0x83DB, 0x03DE, 0x03D4, 0x83D1, 0x83F3, 0x03F6, 0x03FC, 0x83F9, 0x03E8, 0x83ED, 0x83E7, 0x03E2,
+   0x83A3, 0x03A6, 0x03AC, 0x83A9, 0x03B8, 0x83BD, 0x83B7, 0x03B2, 0x0390, 0x8395, 0x839F, 0x039A, 0x838B, 0x038E, 0x0384, 0x8381,
+   0x0280, 0x8285, 0x828F, 0x028A, 0x829B, 0x029E, 0x0294, 0x8291, 0x82B3, 0x02B6, 0x02BC, 0x82B9, 0x02A8, 0x82AD, 0x82A7, 0x02A2,
+   0x82E3, 0x02E6, 0x02EC, 0x82E9, 0x02F8, 0x82FD, 0x82F7, 0x02F2, 0x02D0, 0x82D5, 0x82DF, 0x02DA, 0x82CB, 0x02CE, 0x02C4, 0x82C1,
+   0x8243, 0x0246, 0x024C, 0x8249, 0x0258, 0x825D, 0x8257, 0x0252, 0x0270, 0x8275, 0x827F, 0x027A, 0x826B, 0x026E, 0x0264, 0x8261,
+   0x0220, 0x8225, 0x822F, 0x022A, 0x823B, 0x023E, 0x0234, 0x8231, 0x8213, 0x0216, 0x021C, 0x8219, 0x0208, 0x820D, 0x8207, 0x0202]; 
+
+/** @const {Object} aReverseBitOrder      Table for reversing the bit-order */
+const aReverseBitOrder   = [0x0, 0x8, 0x4, 0xC, 0x2, 0xA, 0x6, 0xE, 0x1, 0x9, 0x5, 0xD, 0x3, 0xB, 0x7, 0xF]; 
+
+//-----------------------------------------------------------------------
+// Imports
+//-----------------------------------------------------------------------
+
+// from JavaScript
+
+// from InkbirdBtThermohumiditySensor
+
+//-----------------------------------------------------------------------
+// Classes 
+//-----------------------------------------------------------------------
+
+//-----------------------------------------------------------------------
+// Exports
+//-----------------------------------------------------------------------
+
+/**
+ * Function to calculate the CRC-16 with the polynomial MODNUS (0x18005) for a buffer
+ * 
+ * @param {Buffer} cBuffer                Buffer object with data
+ * @param {number} iFrom                  Index of first data byte
+ * @param {number} iTo                    Index of last data byte
+ * @param {boolean} bInputReflected       Change the order of the 8 input bits
+ * @param {boolean} bResultReflected      Change the order of the 16 output bits
+ * @param {number} iInitialValue          Initial value to start calculation (usually 0x0000 or 0xFFFF)
+ * @param {number} iFinalXORValue         Value that will be XORed with the result (usually 0x0000 or 0xFFFF)
+ * @returns {number}                      CRC value (undefined if error)
+ */
+module.exports = function (cBuffer, iFrom, iTo, bInputReflected, bResultReflected, iInitialValue, iFinalXORValue)
+{
+   var iCRC = iInitialValue;
+   var iIndex;
+   var iData;
+
+   // Check parameter on plausibility
+   if (((iTo-iFrom+1) > cBuffer.length) || (iTo < iFrom) || (iTo > (cBuffer.length - 1)))
+      return undefined;
+
+   for (var iCnt = iFrom; iCnt <= iTo; iCnt++)
+   {  // work through all the bytes
+      // get byte from buffer
+      iData    = cBuffer.readUIntLE(iCnt, 1);
+      if (bInputReflected)
+      {  // Reverse bitorder on incomming bytes (use table to reverse bitorder in nibbles and swap nibbles)
+         iData = (aReverseBitOrder[iData & 0xF] << 4) | (aReverseBitOrder[(iData >> 4) & 0xF])
+      }
+
+      // Upper byte CRC xor Data for the index to the table
+      iIndex   = iData ^ (iCRC >> 8);
+      // New CRC = Table XOR CRC<<8
+      iCRC     = (aCRCTable[iIndex] ^ (iCRC << 8)) & 0xFFFF;
+   }
+
+   iCRC = ((iCRC ^ iFinalXORValue) & 0xFFFF);
+   if (bResultReflected)
+   {  // Reverse bitorder on result word (use table to reverse bitorder in nibbles and swap nibbles)
+      iCRC = (aReverseBitOrder[ iCRC       & 0xF] << 12) | (aReverseBitOrder[(iCRC >>  4) & 0xF] << 8) | 
+             (aReverseBitOrder[(iCRC >> 8) & 0xF] <<  4) | (aReverseBitOrder[(iCRC >> 12) & 0xF]     );
+   }
+   return iCRC;
+}