Created
March 7, 2013 22:05
-
-
Save chitchcock/5112270 to your computer and use it in GitHub Desktop.
A quick and dirty copy of a C routine for generating a CRC16-CCITT with an intial value of 0xFFFF in Javascript
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
// Modified from http://automationwiki.com/index.php?title=CRC-16-CCITT | |
var crcTable = [0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, | |
0x60c6, 0x70e7, 0x8108, 0x9129, 0xa14a, 0xb16b, | |
0xc18c, 0xd1ad, 0xe1ce, 0xf1ef, 0x1231, 0x0210, | |
0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6, | |
0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, | |
0xf3ff, 0xe3de, 0x2462, 0x3443, 0x0420, 0x1401, | |
0x64e6, 0x74c7, 0x44a4, 0x5485, 0xa56a, 0xb54b, | |
0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d, | |
0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, | |
0x5695, 0x46b4, 0xb75b, 0xa77a, 0x9719, 0x8738, | |
0xf7df, 0xe7fe, 0xd79d, 0xc7bc, 0x48c4, 0x58e5, | |
0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823, | |
0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, | |
0xa90a, 0xb92b, 0x5af5, 0x4ad4, 0x7ab7, 0x6a96, | |
0x1a71, 0x0a50, 0x3a33, 0x2a12, 0xdbfd, 0xcbdc, | |
0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a, | |
0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, | |
0x0c60, 0x1c41, 0xedae, 0xfd8f, 0xcdec, 0xddcd, | |
0xad2a, 0xbd0b, 0x8d68, 0x9d49, 0x7e97, 0x6eb6, | |
0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70, | |
0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, | |
0x9f59, 0x8f78, 0x9188, 0x81a9, 0xb1ca, 0xa1eb, | |
0xd10c, 0xc12d, 0xf14e, 0xe16f, 0x1080, 0x00a1, | |
0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067, | |
0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, | |
0xe37f, 0xf35e, 0x02b1, 0x1290, 0x22f3, 0x32d2, | |
0x4235, 0x5214, 0x6277, 0x7256, 0xb5ea, 0xa5cb, | |
0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d, | |
0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, | |
0x5424, 0x4405, 0xa7db, 0xb7fa, 0x8799, 0x97b8, | |
0xe75f, 0xf77e, 0xc71d, 0xd73c, 0x26d3, 0x36f2, | |
0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634, | |
0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, | |
0xb98a, 0xa9ab, 0x5844, 0x4865, 0x7806, 0x6827, | |
0x18c0, 0x08e1, 0x3882, 0x28a3, 0xcb7d, 0xdb5c, | |
0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a, | |
0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, | |
0x2ab3, 0x3a92, 0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, | |
0xbdaa, 0xad8b, 0x9de8, 0x8dc9, 0x7c26, 0x6c07, | |
0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1, | |
0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, | |
0x8fd9, 0x9ff8, 0x6e17, 0x7e36, 0x4e55, 0x5e74, | |
0x2e93, 0x3eb2, 0x0ed1, 0x1ef0]; | |
function crc16(s) { | |
var crc = 0xFFFF; | |
var j, i; | |
for (i = 0; i < s.length; i++) { | |
c = s.charCodeAt(i); | |
if (c > 255) { | |
throw new RangeError(); | |
} | |
j = (c ^ (crc >> 8)) & 0xFF; | |
crc = crcTable[j] ^ (crc << 8); | |
} | |
return ((crc ^ 0) & 0xFFFF); | |
} | |
document.write("CRC16 of test is 0x" + crc16('test').toString(16) + "<br>"); |
I just wanted to thank you for this JS script.
I was searching online for a [CRC-16 XMODEM] JS script to get me thru a task and found yours, which can be modified to meet the XMODEM CRC
by doing the following:
... just change var crc = 0xFFFF;
to var crc = 0x0000;
NOTE: As far as I know CRC16-CCITT-FALSE
(which is what the change above does) is "%100" equivalent to CRC16-XMODEM
Again: Thank you!
Thanks, working well!
In case of CRC-16/AUG-CCITT initial value should be
var crc = 0x1d0f;
// CCITT-FALSE
// var crc = 0xFFFF;
// https://crates.io/crates/crc16
If you need to pass hex (as i do )
function crc16Hex(...s) {
var crc = 0x1D0F;
var j, i;
for (let c of s) {
if (c > 255) {
throw new RangeError();
}
j = (c ^ (crc >> 8)) & 0xFF;
crc = crcTable[j] ^ (crc << 8);
}
return ((crc ^ 0) & 0xFFFF).toString(16);
}
this works, too, with no lookup table, for buffers & strings:
export const crc16ccitt = (regInit, message) => {
if (typeof message === 'undefined') {
message = regInit
regInit = 0xFFFF
}
if (typeof message === 'string') {
message = message.split('').map(c => c.charCodeAt(0))
}
let crc = regInit + 0
const polynomial = 0x1021
for (const b of message) {
for (let i = 0; i < 8; i++) {
const bit = ((b >> (7 - i) & 1) === 1)
const c15 = ((crc >> 15 & 1) === 1)
crc <<= 1
if (c15 ^ bit) crc ^= polynomial
}
}
crc &= 0xffff
return crc
}
code run success and correct, thank you.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Thanks for the code. FYI, if using the buffer type in node.js , you would need to change from charCodeAt to readUInt8(). There might be a way to auto detect this.
Also for modbus, I was using