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Discussion Groups | Piclist | 16 bit CRC code for PIC

A discussion group for the PICMicro microcontroller. Also called the Microchip PIC, this list is dedicated to the use and abuse of this fine, simple, microcontroller. Close to topic posts are welcome, ie. general electronics.

16 bit CRC code for PIC - taipei6969 - Nov 26 0:43:00 2003

I need to communicate with a device over RS232 and check/generate a
16-bit CRC. Can somebody give me the code to compute 16-bit CRC on
an array of bytes in BASIC or C? The CRC type is called "CRC16
V41". I know there is a standard polynomial used for CRC16 but what
does the "V41" part mean? Thanks for any help.





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Re: 16 bit CRC code for PIC - Phil - Nov 26 12:48:00 2003

its a ccitt standard v4.1. google for "crc v4.1". there is some
source code out there.

--- In , "taipei6969" <taipei6969@y...> wrote:
> I need to communicate with a device over RS232 and check/generate a
> 16-bit CRC. Can somebody give me the code to compute 16-bit CRC on
> an array of bytes in BASIC or C? The CRC type is called "CRC16
> V41". I know there is a standard polynomial used for CRC16 but
what
> does the "V41" part mean? Thanks for any help.



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Re: 16 bit CRC code for PIC - martin de lange - Nov 27 5:53:00 2003

Hi
 
Never seen a V41 but all crc checking results in the same value as we use them across the spectrum for many types of plc's and this is all we use
 
/******************************************************************************
*  Make CRC 16 Look-up Table.                                            *
******************************************************************************/
 
const unsigned int far crc_table[0x100] =
{
 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
};
 
/******************************************************************************
*  Make CRC 16 Calculation Function.                                     *
******************************************************************************/
 
unsigned int Make_Crc (unsigned char __far *data, unsigned int __far len)
{
   unsigned int accum;
 
   /* Pre-conditioning */
   accum = 0xFFFF;
  
   hitdog();  // clock DS1763 Watch dog  //hit the watchdog
 
   while (len--)
   {  accum = ((accum & 0x00FF) << 8) ^
                  crc_table[( (accum >> 8) ^ *data ++ ) & 0x00FF];
   }
 
   hitdog();  // clock DS1763 Watch dog  //hit the watchdog
 
   return(accum);
}
 
regards
Martin
----- Original Message -----
From: taipei6969
To: p...@yahoogroups.com
Sent: Wednesday, November 26, 2003 6:43 PM
Subject: [piclist] 16 bit CRC code for PIC

I need to communicate with a device over RS232 and check/generate a
16-bit CRC.  Can somebody give me the code to compute 16-bit CRC on
an array of bytes in BASIC or C?  The CRC type is called "CRC16
V41".  I know there is a standard polynomial used for CRC16 but what
does the "V41" part mean?  Thanks for any help.

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