CRC-CCITT to CRC16 Modbus implementation

我在使用 PHP 生成 modbus CRC16 代码时遇到了很多麻烦。我在互联网上找到了很多不同的代码，但我已经尝试过了，但由于某种原因我没有得到正确的结果。我找到了一个用于生成CRC16-CCITT的PHP代码。我已经将查找表添加到modbus CRC对应的表，但结果仍然不正确。代码是波纹管。我需要做什么才能将CRC16-CCITT代码转换为CRC16-MODBUS代码。

<?php 
/*************************************************************************
 * phpCrc16 v1.1 -- CRC16/CCITT implementation 
 *
 * By Matteo Beccati <matteo@beccati.com>
 * 
 * Original code by:
 * Ashley Roll
 * Digital Nemesis Pty Ltd
 * www.digitalnemesis.com
 * ash@digitalnemesis.com 
 *
 * Test Vector: "123456789" (character string, no quotes)
 * Generated CRC: 0x29B1
 * 
 *************************************************************************/

/*
 * Returns CRC16 of a string as int value
 */
function CRC16($str)
{
    static $CRC16_Lookup = array(
              0X0000, 0XC0C1, 0XC181, 0X0140, 0XC301, 0X03C0, 0X0280, 0XC241,
        0XC601, 0X06C0, 0X0780, 0XC741, 0X0500, 0XC5C1, 0XC481, 0X0440,
        0XCC01, 0X0CC0, 0X0D80, 0XCD41, 0X0F00, 0XCFC1, 0XCE81, 0X0E40,
        0X0A00, 0XCAC1, 0XCB81, 0X0B40, 0XC901, 0X09C0, 0X0880, 0XC841,
        0XD801, 0X18C0, 0X1980, 0XD941, 0X1B00, 0XDBC1, 0XDA81, 0X1A40,
        0X1E00, 0XDEC1, 0XDF81, 0X1F40, 0XDD01, 0X1DC0, 0X1C80, 0XDC41,
        0X1400, 0XD4C1, 0XD581, 0X1540, 0XD701, 0X17C0, 0X1680, 0XD641,
        0XD201, 0X12C0, 0X1380, 0XD341, 0X1100, 0XD1C1, 0XD081, 0X1040,
        0XF001, 0X30C0, 0X3180, 0XF141, 0X3300, 0XF3C1, 0XF281, 0X3240,
        0X3600, 0XF6C1, 0XF781, 0X3740, 0XF501, 0X35C0, 0X3480, 0XF441,
        0X3C00, 0XFCC1, 0XFD81, 0X3D40, 0XFF01, 0X3FC0, 0X3E80, 0XFE41,
        0XFA01, 0X3AC0, 0X3B80, 0XFB41, 0X3900, 0XF9C1, 0XF881, 0X3840,
        0X2800, 0XE8C1, 0XE981, 0X2940, 0XEB01, 0X2BC0, 0X2A80, 0XEA41,
        0XEE01, 0X2EC0, 0X2F80, 0XEF41, 0X2D00, 0XEDC1, 0XEC81, 0X2C40,
        0XE401, 0X24C0, 0X2580, 0XE541, 0X2700, 0XE7C1, 0XE681, 0X2640,
        0X2200, 0XE2C1, 0XE381, 0X2340, 0XE101, 0X21C0, 0X2080, 0XE041,
        0XA001, 0X60C0, 0X6180, 0XA141, 0X6300, 0XA3C1, 0XA281, 0X6240,
        0X6600, 0XA6C1, 0XA781, 0X6740, 0XA501, 0X65C0, 0X6480, 0XA441,
        0X6C00, 0XACC1, 0XAD81, 0X6D40, 0XAF01, 0X6FC0, 0X6E80, 0XAE41,
        0XAA01, 0X6AC0, 0X6B80, 0XAB41, 0X6900, 0XA9C1, 0XA881, 0X6840,
        0X7800, 0XB8C1, 0XB981, 0X7940, 0XBB01, 0X7BC0, 0X7A80, 0XBA41,
        0XBE01, 0X7EC0, 0X7F80, 0XBF41, 0X7D00, 0XBDC1, 0XBC81, 0X7C40,
        0XB401, 0X74C0, 0X7580, 0XB541, 0X7700, 0XB7C1, 0XB681, 0X7640,
        0X7200, 0XB2C1, 0XB381, 0X7340, 0XB101, 0X71C0, 0X7080, 0XB041,
        0X5000, 0X90C1, 0X9181, 0X5140, 0X9301, 0X53C0, 0X5280, 0X9241,
        0X9601, 0X56C0, 0X5780, 0X9741, 0X5500, 0X95C1, 0X9481, 0X5440,
        0X9C01, 0X5CC0, 0X5D80, 0X9D41, 0X5F00, 0X9FC1, 0X9E81, 0X5E40,
        0X5A00, 0X9AC1, 0X9B81, 0X5B40, 0X9901, 0X59C0, 0X5880, 0X9841,
        0X8801, 0X48C0, 0X4980, 0X8941, 0X4B00, 0X8BC1, 0X8A81, 0X4A40,
        0X4E00, 0X8EC1, 0X8F81, 0X4F40, 0X8D01, 0X4DC0, 0X4C80, 0X8C41,
        0X4400, 0X84C1, 0X8581, 0X4540, 0X8701, 0X47C0, 0X4680, 0X8641,
        0X8201, 0X42C0, 0X4380, 0X8341, 0X4100, 0X81C1, 0X8081, 0X4040
    );
    $crc16 = 0xFFFF; // the CRC
    $len = strlen($str);
    for($i = 0; $i < $len; $i++ )
    {
        $t = ($crc16 >> 8) ^ ord($str[$i]); // High byte Xor Message Byte to get index
        $crc16 = (($crc16 << 8) & 0xffff) ^ $CRC16_Lookup[$t]; // Update the CRC from table
    }
    // crc16 now contains the CRC value
    return $crc16;
}
/*
 * Returns CRC16 of a string as hexadecimal string
 */
function CRC16HexDigest($str)
{
    return sprintf('%04X', crc16($str));
}
echo CRC16HexDigest('123456789');
?>

这个Pascal代码段是MODBUS RTU（ASCII不同）协议在线计算，没有任何表格：

function mb_CalcCRC16(ptr: pointer to byte; ByteCount: byte): word;
var
  crc: word;
  b, i, n: byte;
begin
  crc := $FFFF;
  for i := 0 to ByteCount do
    if i = 0 then           // device id is 1st byte in message, and it is not in the buffer
      b := mb_GetMessageID; // so we have to calculate it and put it as 1st crc byte
    else
      b := ptr^;
      Inc(ptr);
    endif;
    crc := crc xor word(b);
    for n := 1 to 8 do
      if (crc and 1) = 1 then
        crc := (crc shr 1) xor $A001;
      else
        crc := crc shr 1;
      endif;
    endfor;
  endfor;
  Return(crc);
end;
function mb_CalcCRC: word; // Calculate CRC for message in mb_pdu
begin // this message can be one that is just received, or in a reply we have just composed
  Return(mb_CalcCRC16(@mb_pdu[1], mb_GetEndOfData));
end;

这是来自具有

MODBUS RTU从站协议的工作嵌入式AVR设备的引述。

这

比查找表快

 function crc16($data)
 {
   $crc = 0xFFFF;
   for ($i = 0; $i < strlen($data); $i++)
   {
     $crc ^=ord($data[$i]);
        for ($j = 8; $j !=0; $j--)
        {
            if (($crc & 0x0001) !=0)
            {
                $crc >>= 1;
                $crc ^= 0xA001;
            }
            else
                $crc >>= 1;
        }
    }   
   return $crc;
 }

多年后，你的答案对我来说非常有用。我将你的答案组合在一个非查找表解决方案中：

function crc16_modbus($msg)
{
    $data = pack('H*',$msg);
    $crc = 0xFFFF;
    for ($i = 0; $i < strlen($data); $i++)
    {
        $crc ^=ord($data[$i]);
        for ($j = 8; $j !=0; $j--)
        {
            if (($crc & 0x0001) !=0)
            {
                $crc >>= 1;
                $crc ^= 0xA001;
            }
            else $crc >>= 1;
        }
    }   
    return sprintf('%04X', $crc);
}

我等待的结果与在线工具一致，例如：

拉默特比斯
塔哈帕克苏

感谢您的回复。我能够使用以下代码在PHP中执行Modbus crc检查：

<?php   
    //Calcula o CRC para uma mensagem modbus
    function modbus_crc($modbus_msg){
        $crctab16 = [0X0000, 0XC0C1, 0XC181, 0X0140, 0XC301, 0X03C0, 0X0280, 0XC241,
            0XC601, 0X06C0, 0X0780, 0XC741, 0X0500, 0XC5C1, 0XC481, 0X0440,
            0XCC01, 0X0CC0, 0X0D80, 0XCD41, 0X0F00, 0XCFC1, 0XCE81, 0X0E40,
            0X0A00, 0XCAC1, 0XCB81, 0X0B40, 0XC901, 0X09C0, 0X0880, 0XC841,
            0XD801, 0X18C0, 0X1980, 0XD941, 0X1B00, 0XDBC1, 0XDA81, 0X1A40,
            0X1E00, 0XDEC1, 0XDF81, 0X1F40, 0XDD01, 0X1DC0, 0X1C80, 0XDC41,
            0X1400, 0XD4C1, 0XD581, 0X1540, 0XD701, 0X17C0, 0X1680, 0XD641,
            0XD201, 0X12C0, 0X1380, 0XD341, 0X1100, 0XD1C1, 0XD081, 0X1040,
            0XF001, 0X30C0, 0X3180, 0XF141, 0X3300, 0XF3C1, 0XF281, 0X3240,
            0X3600, 0XF6C1, 0XF781, 0X3740, 0XF501, 0X35C0, 0X3480, 0XF441,
            0X3C00, 0XFCC1, 0XFD81, 0X3D40, 0XFF01, 0X3FC0, 0X3E80, 0XFE41,
            0XFA01, 0X3AC0, 0X3B80, 0XFB41, 0X3900, 0XF9C1, 0XF881, 0X3840,
            0X2800, 0XE8C1, 0XE981, 0X2940, 0XEB01, 0X2BC0, 0X2A80, 0XEA41,
            0XEE01, 0X2EC0, 0X2F80, 0XEF41, 0X2D00, 0XEDC1, 0XEC81, 0X2C40,
            0XE401, 0X24C0, 0X2580, 0XE541, 0X2700, 0XE7C1, 0XE681, 0X2640,
            0X2200, 0XE2C1, 0XE381, 0X2340, 0XE101, 0X21C0, 0X2080, 0XE041,
            0XA001, 0X60C0, 0X6180, 0XA141, 0X6300, 0XA3C1, 0XA281, 0X6240,
            0X6600, 0XA6C1, 0XA781, 0X6740, 0XA501, 0X65C0, 0X6480, 0XA441,
            0X6C00, 0XACC1, 0XAD81, 0X6D40, 0XAF01, 0X6FC0, 0X6E80, 0XAE41,
            0XAA01, 0X6AC0, 0X6B80, 0XAB41, 0X6900, 0XA9C1, 0XA881, 0X6840,
            0X7800, 0XB8C1, 0XB981, 0X7940, 0XBB01, 0X7BC0, 0X7A80, 0XBA41,
            0XBE01, 0X7EC0, 0X7F80, 0XBF41, 0X7D00, 0XBDC1, 0XBC81, 0X7C40,
            0XB401, 0X74C0, 0X7580, 0XB541, 0X7700, 0XB7C1, 0XB681, 0X7640,
            0X7200, 0XB2C1, 0XB381, 0X7340, 0XB101, 0X71C0, 0X7080, 0XB041,
            0X5000, 0X90C1, 0X9181, 0X5140, 0X9301, 0X53C0, 0X5280, 0X9241,
            0X9601, 0X56C0, 0X5780, 0X9741, 0X5500, 0X95C1, 0X9481, 0X5440,
            0X9C01, 0X5CC0, 0X5D80, 0X9D41, 0X5F00, 0X9FC1, 0X9E81, 0X5E40,
            0X5A00, 0X9AC1, 0X9B81, 0X5B40, 0X9901, 0X59C0, 0X5880, 0X9841,
            0X8801, 0X48C0, 0X4980, 0X8941, 0X4B00, 0X8BC1, 0X8A81, 0X4A40,
            0X4E00, 0X8EC1, 0X8F81, 0X4F40, 0X8D01, 0X4DC0, 0X4C80, 0X8C41,
            0X4400, 0X84C1, 0X8581, 0X4540, 0X8701, 0X47C0, 0X4680, 0X8641,
            0X8201, 0X42C0, 0X4380, 0X8341, 0X4100, 0X81C1, 0X8081, 0X4040];
        $hexdata = pack('H*',$modbus_msg);
        $nLength = strlen($hexdata);
        $fcs = 0xFFFF;
        $pos = 0;
        while($nLength > 0)
        {
            $fcs = ($fcs >> 8) ^ $crctab16[($fcs ^ ord($hexdata[$pos])) & 0xFF];
            $nLength--;
            $pos++;
        }
        $crc_semi_inverted = sprintf('%04X', $fcs);//modbus crc invert the hight and low bit so we need to put the last two letter in the begining
        $crc_modbus = substr($crc_semi_inverted,2,2).substr($crc_semi_inverted,0,2);
        return $crc_modbus;
    }
?>

您应该输入一个带有十六进制消息的字符串：

$modbus_msg='01040000002';$modbus_msg_crc=modbus_crc（$modbus_msg）;

这是用于ModBus RTU的CRC16-ANSI（IBM）算法的紧凑版本。

function crc16_ansi($data) {
  $crc = 0xFFFF;
  for ($i = 0; $i < strlen($data); $i++){
    $crc ^= ord($data[$i]);
    for($j = 8; $j--;)
      $crc = $crc & 0x0001 ? $crc = ($crc >> 1) ^ 0xA001 : $crc >> 1;
  }
  return $crc;
}

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