I need to communicate with a RS232 device, I have no specs or information available. I send a 16 byte command and get a 16 byte result back. The last byte looks like some kind of crc or checksum, I have tried using this http://miscel.dk/MiscEl/miscelCRCandChecksum.html with no luck. Anyone can reverse engineer the crc/checksum algorithm? here is some data captured with an RS-232 monitor program: 01 80 42 00 00 00 00 00 00 00 00 00 00 00 01 B3 01 80 42 00 00 00 00 00 00 00 00 00 00 00 02 51 01 80 42 00 00 00 00 00 00 00 00 00 00 00 03 0F 01 80 42 00 00 00 00 00 00 00 00 00 00 00 04 8C 01 80 42 00 00 00 00 00 00 00 00 00 00 00 05 D2 01 80 42 00 00 00 00 00 00 00 00 00 00 00 06 30 01 80 42 00 00 00 00 00 00 00 00 00 00 00 07 6E 01 80 42 00 00 00 00 00 00 00 00 00 00 00 08 2F 01 80 42 00 00 00 00 00 00 00 00 00 00 00 09 71 01 80 42 00 00 00 00 00 00 00 00 00 00 00 0A 93 01 80 42 00 00 00 00 00 00 00 00 00 00 00 0B CD 01 80 42 00 00 00 00 00 00 00 00 00 00 00 0C 4E 01 80 42 00 00 00 00 00 00 00 00 00 00 00 0D 10 01 80 42 00 00 00 00 00 00 00 00 00 00 00 0E F2 01 80 42 00 00 00 00 00 00 00 00 00 00 00 0F AC 01 80 42 00 00 00 00 00 00 00 00 00 00 00 10 70 01 80 42 00 00 00 00 00 00 00 00 00 00 00 11 2E 01 80 42 00 00 00 00 00 00 00 00 00 00 00 12 CC 01 80 42 00 00 00 00 00 00 00 00 00 00 00 13 92 01 80 42 00 00 00 00 00 00 00 00 00 00 00 14 11 01 80 42 00 00 00 00 00 00 00 00 00 00 00 15 4F 01 80 42 00 00 00 00 00 00 00 00 00 00 00 16 AD 01 80 42 00 00 00 00 00 00 00 00 00 00 00 17 F3 01 80 42 00 00 00 00 00 00 00 00 00 00 00 18 B2 01 80 42 00 00 00 00 00 00 00 00 00 00 00 19 EC 01 80 42 00 00 00 00 00 00 00 00 00 00 00 1A 0E 01 80 42 00 00 00 00 00 00 00 00 00 00 00 1B 50 01 80 42 00 00 00 00 00 00 00 00 00 00 00 1C D3 01 80 42 00 00 00 00 00 00 00 00 00 00 00 1D 8D 01 80 42 00 00 00 00 00 00 00 00 00 00 00 1E 6F 01 80 42 00 00 00 00 00 00 00 00 00 00 00 1F 31 01 80 42 00 00 00 00 00 00 00 00 00 00 00 20 CE 01 80 42 00 00 00 00 00 00 00 00 00 00 00 21 90 01 80 42 00 00 00 00 00 00 00 00 00 00 00 22 72 01 80 42 00 00 00 00 00 00 00 00 00 00 00 23 2C 01 80 42 00 00 00 00 00 00 00 00 00 00 00 24 AF 01 80 42 00 00 00 00 00 00 00 00 00 00 00 25 F1 01 80 42 00 00 00 00 00 00 00 00 00 00 00 26 13 01 80 42 00 00 00 00 00 00 00 00 00 00 00 27 4D 01 80 42 00 00 00 00 00 00 00 00 00 00 00 28 0C 01 80 42 00 00 00 00 00 00 00 00 00 00 00 29 52 01 80 42 00 00 00 00 00 00 00 00 00 00 00 2A B0 01 80 42 00 00 00 00 00 00 00 00 00 00 00 2B EE 01 80 42 00 00 00 00 00 00 00 00 00 00 00 2C 6D 01 80 42 00 00 00 00 00 00 00 00 00 00 00 2D 33 01 80 42 00 00 00 00 00 00 00 00 00 00 00 2E D1 01 80 42 00 00 00 00 00 00 00 00 00 00 00 2F 8F 01 80 42 00 00 00 00 00 00 00 00 00 00 00 30 53 01 80 42 00 00 00 00 00 00 00 00 00 00 00 31 0D 01 80 42 00 00 00 00 00 00 00 00 00 00 00 32 EF 01 80 42 00 00 00 00 00 00 00 00 00 00 00 33 B1 01 80 42 00 00 00 00 00 00 00 00 00 00 00 34 32 01 80 42 00 00 00 00 00 00 00 00 00 00 00 35 6C 01 80 42 00 00 00 00 00 00 00 00 00 00 00 36 8E 01 80 42 00 00 00 00 00 00 00 00 00 00 00 37 D0 01 80 42 00 00 00 00 00 00 00 00 00 00 00 38 91 01 80 42 00 00 00 00 00 00 00 00 00 00 00 39 CF 01 80 42 00 00 00 00 00 00 00 00 00 00 00 3A 2D 01 80 42 00 00 00 00 00 00 00 00 00 00 00 3B 73 01 80 42 00 00 00 00 00 00 00 00 00 00 00 3C F0 01 80 42 00 00 00 00 00 00 00 00 00 00 00 3D AE 01 80 42 00 00 00 00 00 00 00 00 00 00 00 3E 4C 01 80 42 00 00 00 00 00 00 00 00 00 00 00 3F 12 01 80 42 00 00 00 00 00 00 00 00 00 00 00 40 AB 01 80 42 00 00 00 00 00 00 00 00 00 00 00 41 F5 01 80 42 00 00 00 00 00 00 00 00 00 00 00 42 17 01 80 42 00 00 00 00 00 00 00 00 00 00 00 43 49 01 80 42 00 00 00 00 00 00 00 00 00 00 00 44 CA 01 80 42 00 00 00 00 00 00 00 00 00 00 00 45 94 01 80 42 00 00 00 00 00 00 00 00 00 00 00 46 76 01 80 42 00 00 00 00 00 00 00 00 00 00 00 47 28 01 80 42 00 00 00 00 00 00 00 00 00 00 00 48 69 01 80 42 00 00 00 00 00 00 00 00 00 00 00 49 37 01 80 42 00 00 00 00 00 00 00 00 00 00 00 4A D5 01 80 42 00 00 00 00 00 00 00 00 00 00 00 4B 8B 01 80 42 00 00 00 00 00 00 00 00 00 00 00 4C 08 01 80 42 00 00 00 00 00 00 00 00 00 00 00 4D 56 01 80 42 00 00 00 00 00 00 00 00 00 00 00 4E B4 01 80 42 00 00 00 00 00 00 00 00 00 00 00 4F EA 01 80 42 00 00 00 00 00 00 00 00 00 00 00 50 36 01 80 42 00 00 00 00 00 00 00 00 00 00 00 51 68 01 80 42 00 00 00 00 00 00 00 00 00 00 00 52 8A 01 80 42 00 00 00 00 00 00 00 00 00 00 00 53 D4 01 80 42 00 00 00 00 00 00 00 00 00 00 00 54 57 01 80 42 00 00 00 00 00 00 00 00 00 00 00 55 09 01 80 42 00 00 00 00 00 00 00 00 00 00 00 56 EB 01 80 42 00 00 00 00 00 00 00 00 00 00 00 57 B5 01 80 42 00 00 00 00 00 00 00 00 00 00 00 58 F4 01 80 42 00 00 00 00 00 00 00 00 00 00 00 59 AA 01 80 42 00 00 00 00 00 00 00 00 00 00 00 5A 48 01 80 42 00 00 00 00 00 00 00 00 00 00 00 5B 16 01 80 42 00 00 00 00 00 00 00 00 00 00 00 5C 95 01 80 42 00 00 00 00 00 00 00 00 00 00 00 5D CB 01 80 42 00 00 00 00 00 00 00 00 00 00 00 5E 29 01 80 42 00 00 00 00 00 00 00 00 00 00 00 5F 77 01 80 42 00 00 00 00 00 00 00 00 00 00 00 60 88 01 80 42 00 00 00 00 00 00 00 00 00 00 00 61 D6 01 80 42 00 00 00 00 00 00 00 00 00 00 00 62 34 01 80 42 00 00 00 00 00 00 00 00 00 00 00 63 6A 01 80 42 00 00 00 00 00 00 00 00 00 00 00 64 E9 01 80 42 00 00 00 00 00 00 00 00 00 00 00 65 B7 01 80 42 00 00 00 00 00 00 00 00 00 00 00 66 55 01 80 42 00 00 00 00 00 00 00 00 00 00 00 67 0B 01 80 42 00 00 00 00 00 00 00 00 00 00 00 68 4A 01 80 42 00 00 00 00 00 00 00 00 00 00 00 69 14 01 80 42 00 00 00 00 00 00 00 00 00 00 00 6A F6 01 80 42 00 00 00 00 00 00 00 00 00 00 00 6B A8 01 80 42 00 00 00 00 00 00 00 00 00 00 00 6C 2B 01 80 42 00 00 00 00 00 00 00 00 00 00 00 6D 75 01 80 42 00 00 00 00 00 00 00 00 00 00 00 6E 97 01 80 42 00 00 00 00 00 00 00 00 00 00 00 6F C9 01 80 42 00 00 00 00 00 00 00 00 00 00 00 70 15 01 80 42 00 00 00 00 00 00 00 00 00 00 00 71 4B 01 80 42 00 00 00 00 00 00 00 00 00 00 00 72 A9 01 80 42 00 00 00 00 00 00 00 00 00 00 00 73 F7 01 80 42 00 00 00 00 00 00 00 00 00 00 00 74 74 01 80 42 00 00 00 00 00 00 00 00 00 00 00 75 2A 01 80 42 00 00 00 00 00 00 00 00 00 00 00 76 C8 01 80 42 00 00 00 00 00 00 00 00 00 00 00 77 96 01 80 42 00 00 00 00 00 00 00 00 00 00 00 78 D7 01 80 42 00 00 00 00 00 00 00 00 00 00 00 79 89 01 80 42 00 00 00 00 00 00 00 00 00 00 00 7A 6B 01 80 42 00 00 00 00 00 00 00 00 00 00 00 7B 35 01 80 42 00 00 00 00 00 00 00 00 00 00 00 7C B6 01 80 42 00 00 00 00 00 00 00 00 00 00 00 7D E8 01 80 42 00 00 00 00 00 00 00 00 00 00 00 7E 0A 01 80 42 00 00 00 00 00 00 00 00 00 00 00 7F 54 01 80 42 00 00 00 00 00 00 00 00 00 00 00 80 61 01 80 42 00 00 00 00 00 00 00 00 00 00 00 81 3F 01 80 42 00 00 00 00 00 00 00 00 00 00 00 82 DD 01 80 42 00 00 00 00 00 00 00 00 00 00 00 83 83 01 80 42 00 00 00 00 00 00 00 00 00 00 00 84 00 01 80 42 00 00 00 00 00 00 00 00 00 00 00 85 5E 01 80 42 00 00 00 00 00 00 00 00 00 00 00 86 BC 01 80 42 00 00 00 00 00 00 00 00 00 00 00 87 E2 01 80 42 00 00 00 00 00 00 00 00 00 00 00 88 A3 01 80 42 00 00 00 00 00 00 00 00 00 00 00 89 FD 01 80 42 00 00 00 00 00 00 00 00 00 00 00 8A 1F 01 80 42 00 00 00 00 00 00 00 00 00 00 00 8B 41 01 80 42 00 00 00 00 00 00 00 00 00 00 00 8C C2 01 80 42 00 00 00 00 00 00 00 00 00 00 00 8D 9C 01 80 42 00 00 00 00 00 00 00 00 00 00 00 8E 7E 01 80 42 00 00 00 00 00 00 00 00 00 00 00 8F 20 01 80 42 00 00 00 00 00 00 00 00 00 00 00 90 FC 01 80 42 00 00 00 00 00 00 00 00 00 00 00 91 A2 01 80 42 00 00 00 00 00 00 00 00 00 00 00 92 40 01 80 42 00 00 00 00 00 00 00 00 00 00 00 93 1E 01 80 42 00 00 00 00 00 00 00 00 00 00 00 94 9D 01 80 42 00 00 00 00 00 00 00 00 00 00 00 95 C3 01 80 42 00 00 00 00 00 00 00 00 00 00 00 96 21 01 80 42 00 00 00 00 00 00 00 00 00 00 00 97 7F 01 80 42 00 00 00 00 00 00 00 00 00 00 00 98 3E 01 80 42 00 00 00 00 00 00 00 00 00 00 00 99 60 01 80 42 00 00 00 00 00 00 00 00 00 00 00 9A 82 01 80 42 00 00 00 00 00 00 00 00 00 00 00 9B DC 01 80 42 00 00 00 00 00 00 00 00 00 00 00 9C 5F 01 80 42 00 00 00 00 00 00 00 00 00 00 00 9D 01 01 80 42 00 00 00 00 00 00 00 00 00 00 00 9E E3 01 80 42 00 00 00 00 00 00 00 00 00 00 00 9F BD 01 80 42 00 00 00 00 00 00 00 00 00 00 00 A0 42 01 80 42 00 00 00 00 00 00 00 00 00 00 00 A1 1C 01 80 42 00 00 00 00 00 00 00 00 00 00 00 A2 FE 01 80 42 00 00 00 00 00 00 00 00 00 00 00 A3 A0 01 80 42 00 00 00 00 00 00 00 00 00 00 00 A4 23 01 80 42 00 00 00 00 00 00 00 00 00 00 00 A5 7D 01 80 42 00 00 00 00 00 00 00 00 00 00 00 A6 9F 01 80 42 00 00 00 00 00 00 00 00 00 00 00 A7 C1 01 80 42 00 00 00 00 00 00 00 00 00 00 00 A8 80 01 80 42 00 00 00 00 00 00 00 00 00 00 00 A9 DE 01 80 42 00 00 00 00 00 00 00 00 00 00 00 AA 3C 01 80 42 00 00 00 00 00 00 00 00 00 00 00 AB 62 01 80 42 00 00 00 00 00 00 00 00 00 00 00 AC E1 01 80 42 00 00 00 00 00 00 00 00 00 00 00 AD BF 01 80 42 00 00 00 00 00 00 00 00 00 00 00 AE 5D 01 80 42 00 00 00 00 00 00 00 00 00 00 00 AF 03 01 80 42 00 00 00 00 00 00 00 00 00 00 00 B0 DF 01 80 42 00 00 00 00 00 00 00 00 00 00 00 B1 81 01 80 42 00 00 00 00 00 00 00 00 00 00 00 B2 63 01 80 42 00 00 00 00 00 00 00 00 00 00 00 B3 3D 01 80 42 00 00 00 00 00 00 00 00 00 00 00 B4 BE 01 80 42 00 00 00 00 00 00 00 00 00 00 00 B5 E0 01 80 42 00 00 00 00 00 00 00 00 00 00 00 B6 02 01 80 42 00 00 00 00 00 00 00 00 00 00 00 B7 5C 01 80 42 00 00 00 00 00 00 00 00 00 00 00 B8 1D 01 80 42 00 00 00 00 00 00 00 00 00 00 00 B9 43 01 80 42 00 00 00 00 00 00 00 00 00 00 00 BA A1 01 80 42 00 00 00 00 00 00 00 00 00 00 00 BB FF 01 80 42 00 00 00 00 00 00 00 00 00 00 00 BC 7C 01 80 42 00 00 00 00 00 00 00 00 00 00 00 BD 22 01 80 42 00 00 00 00 00 00 00 00 00 00 00 BE C0 01 80 42 00 00 00 00 00 00 00 00 00 00 00 BF 9E 01 80 42 00 00 00 00 00 00 00 00 00 00 00 C0 27 01 80 42 00 00 00 00 00 00 00 00 00 00 00 C1 79 01 80 42 00 00 00 00 00 00 00 00 00 00 00 C2 9B 01 80 42 00 00 00 00 00 00 00 00 00 00 00 C3 C5 01 80 42 00 00 00 00 00 00 00 00 00 00 00 C4 46 01 80 42 00 00 00 00 00 00 00 00 00 00 00 C5 18 01 80 42 00 00 00 00 00 00 00 00 00 00 00 C6 FA 01 80 42 00 00 00 00 00 00 00 00 00 00 00 C7 A4 01 80 42 00 00 00 00 00 00 00 00 00 00 00 C8 E5 01 80 42 00 00 00 00 00 00 00 00 00 00 00 C9 BB 01 80 42 00 00 00 00 00 00 00 00 00 00 00 CA 59 01 80 42 00 00 00 00 00 00 00 00 00 00 00 CB 07 01 80 42 00 00 00 00 00 00 00 00 00 00 00 CC 84 01 80 42 00 00 00 00 00 00 00 00 00 00 00 CD DA 01 80 42 00 00 00 00 00 00 00 00 00 00 00 CE 38 01 80 42 00 00 00 00 00 00 00 00 00 00 00 CF 66 01 80 42 00 00 00 00 00 00 00 00 00 00 00 D0 BA 01 80 42 00 00 00 00 00 00 00 00 00 00 00 D1 E4 01 80 42 00 00 00 00 00 00 00 00 00 00 00 D2 06 01 80 42 00 00 00 00 00 00 00 00 00 00 00 D3 58 01 80 42 00 00 00 00 00 00 00 00 00 00 00 D4 DB 01 80 42 00 00 00 00 00 00 00 00 00 00 00 D5 85 01 80 42 00 00 00 00 00 00 00 00 00 00 00 D6 67 01 80 42 00 00 00 00 00 00 00 00 00 00 00 D7 39 01 80 42 00 00 00 00 00 00 00 00 00 00 00 D8 78 01 80 42 00 00 00 00 00 00 00 00 00 00 00 D9 26 01 80 42 00 00 00 00 00 00 00 00 00 00 00 DA C4 01 80 42 00 00 00 00 00 00 00 00 00 00 00 DB 9A 01 80 42 00 00 00 00 00 00 00 00 00 00 00 DC 19 01 80 42 00 00 00 00 00 00 00 00 00 00 00 DD 47 01 80 42 00 00 00 00 00 00 00 00 00 00 00 DE A5 01 80 42 00 00 00 00 00 00 00 00 00 00 00 DF FB 01 80 42 00 00 00 00 00 00 00 00 00 00 00 E0 04 01 80 42 00 00 00 00 00 00 00 00 00 00 00 E1 5A 01 80 42 00 00 00 00 00 00 00 00 00 00 00 E2 B8 01 80 42 00 00 00 00 00 00 00 00 00 00 00 E3 E6 01 80 42 00 00 00 00 00 00 00 00 00 00 00 E4 65 01 80 42 00 00 00 00 00 00 00 00 00 00 00 E5 3B 01 80 42 00 00 00 00 00 00 00 00 00 00 00 E6 D9 01 80 42 00 00 00 00 00 00 00 00 00 00 00 E7 87 01 80 42 00 00 00 00 00 00 00 00 00 00 00 E8 C6 01 80 42 00 00 00 00 00 00 00 00 00 00 00 E9 98 01 80 42 00 00 00 00 00 00 00 00 00 00 00 EA 7A 01 80 42 00 00 00 00 00 00 00 00 00 00 00 EB 24 01 80 42 00 00 00 00 00 00 00 00 00 00 00 EC A7 01 80 42 00 00 00 00 00 00 00 00 00 00 00 ED F9 01 80 42 00 00 00 00 00 00 00 00 00 00 00 EE 1B 01 80 42 00 00 00 00 00 00 00 00 00 00 00 EF 45 01 80 42 00 00 00 00 00 00 00 00 00 00 00 F0 99 01 80 42 00 00 00 00 00 00 00 00 00 00 00 F1 C7 01 80 42 00 00 00 00 00 00 00 00 00 00 00 F2 25 01 80 42 00 00 00 00 00 00 00 00 00 00 00 F3 7B 01 80 42 00 00 00 00 00 00 00 00 00 00 00 F4 F8 01 80 42 00 00 00 00 00 00 00 00 00 00 00 F5 A6 01 80 42 00 00 00 00 00 00 00 00 00 00 00 F6 44 01 80 42 00 00 00 00 00 00 00 00 00 00 00 F7 1A 01 80 42 00 00 00 00 00 00 00 00 00 00 00 F8 5B 01 80 42 00 00 00 00 00 00 00 00 00 00 00 F9 05 01 80 42 00 00 00 00 00 00 00 00 00 00 00 FA E7 01 80 42 00 00 00 00 00 00 00 00 00 00 00 FB B9 01 80 42 00 00 00 00 00 00 00 00 00 00 00 FC 3A 01 80 42 00 00 00 00 00 00 00 00 00 00 00 FD 64 01 80 42 00 00 00 00 00 00 00 00 00 00 00 FE 86 01 80 42 00 00 00 00 00 00 00 00 00 00 00 FF D8 The second to last byte seems to be a sequential number that starts over at 00 when it reaches FF. I have included the whole range from 00 to FF to make it easier to guess the crc/checksum method.