Based on one of the many examples in this forum: How can CRC16 XModem accept Hex Input - #2 by Steve-Mcl
A common approach is to use a well established lib. e.g. easy-crc.
Demo of easy-crc
Flow (use CTRL-I to import)
[{"id":"e2beeb574d982801","type":"inject","z":"b0865f2b12f5f1a6","name":"","props":[{"p":"payload"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"01C80101C900000000000000","payloadType":"str","x":1090,"y":140,"wires":[["4bf21b40a1445e15"]]},{"id":"4bf21b40a1445e15","type":"function","z":"b0865f2b12f5f1a6","name":"easy-crc","func":"//See https://www.npmjs.com/package/easy-crc?activeTab=readme for list of supported algorithms\n\n/*\nSupported CRC32 algorithms:\nCRC-32\nCRC-32C\nCRC-32D\nCRC-32Q\nBZIP2\nJAMCRC\nMPEG-2\nPOSIX\nXFER\n*/\n\nconst { crc32 } = easyCrc;\nconst data = Buffer.from(msg.payload, 'hex');\nmsg.payload = {} \n\nmsg.payload.CRC32 = crc32('CRC-32', data)\nmsg.payload.CRC32C = crc32('CRC-32C', data)\nmsg.payload.CRC32D = crc32('CRC-32D', data)\nmsg.payload.CRC32Q = crc32('CRC-32Q', data)\nmsg.payload.BZIP2 = crc32('BZIP2', data)\nmsg.payload.JAMCRC = crc32('JAMCRC', data)\nmsg.payload.MPEG2 = crc32('MPEG-2', data)\nmsg.payload.POSIX = crc32('POSIX', data)\nmsg.payload.XFER = crc32('XFER', data)\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[{"var":"easyCrc","module":"easy-crc"}],"x":1100,"y":200,"wires":[["25cd665db5eaa0d9"]]},{"id":"25cd665db5eaa0d9","type":"debug","z":"b0865f2b12f5f1a6","name":"","active":true,"tosidebar":true,"console":false,"tostatus":true,"complete":"payload","targetType":"msg","statusVal":"payload","statusType":"auto","x":1130,"y":260,"wires":[]}]
If you are adverse to using NPM modules in your function nodes then here is a hand coded "CRC-32"
[{"id":"8cfbeeef9e2ee878","type":"inject","z":"b0865f2b12f5f1a6","name":"","props":[{"p":"payload"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"01C80101C900000000000000","payloadType":"str","x":1090,"y":400,"wires":[["d72681dcdc9878a5"]]},{"id":"d72681dcdc9878a5","type":"function","z":"b0865f2b12f5f1a6","name":"hand coded CRC32","func":"\nconst buffer = Buffer.from(msg.payload, 'hex');\n\nconst makeCRCTable = function () {\n let c;\n const crcTable = [];\n for (let n = 0; n < 256; n++) {\n c = n;\n for (let k = 0; k < 8; k++) {\n c = ((c & 1) ? (0xEDB88320 ^ (c >>> 1)) : (c >>> 1));\n }\n crcTable[n] = c;\n }\n return crcTable;\n}\n\nconst crc32 = function (buffer) {\n const crcTable = context.crcTable || (context.crcTable = makeCRCTable());\n context.crcTable = crcTable\n let crc = 0 ^ (-1);\n for (let i = 0; i < buffer.length; i++) {\n crc = (crc >>> 8) ^ crcTable[(crc ^ buffer[i]) & 0xFF];\n }\n return (crc ^ (-1)) >>> 0;\n};\n\n\nmsg.payload = crc32(buffer)\nreturn msg\n\n\n","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":1130,"y":460,"wires":[["76586e5b0b84bcc8"]]},{"id":"76586e5b0b84bcc8","type":"debug","z":"b0865f2b12f5f1a6","name":"","active":true,"tosidebar":true,"console":false,"tostatus":true,"complete":"payload","targetType":"msg","statusVal":"payload","statusType":"auto","x":1130,"y":520,"wires":[]}]
