CRC

[Carlos Bruno Silva]

My board is an Atmel TSC695. I have checked the docs I have but so far 
did not find anything about a CRC routine in the debug monitor. Do you 
know if it has one?

Carlos S.

Kamen Penev wrote:

> Carlos,
>
> Depending on the generative polynomial you can get different formulas 
> for computing a CRC. I am attaching a program that generates several 
> popular varieties of CRC routines. I've used a couple of them 
> successfully.
> I don't know who the author is. I got this off the Net.
>
> But before you go any further, see if the debug monitor (if you have 
> one) on your board already provides a CRC routine. Many do.
>
> Kamen
>
> ----------------------
> /* This program will write six C routines for the calculation of
> * the following CRC's. */
>
> /* The CRC polynomial.
> * These 4 values define the crc-polynomial.
> * If you change them, you must change crctab[]'s initial value to what is
> * printed by initcrctab() [see 'compile with -DMAKETAB' above].
> */
>
> /* This tables assumes CCITT is MSB first.  Swapped means LSB first.   
> In that
> * case the polynomial is also swapped
> */
>
> /* 16 bit crc's */
> /* Value used by:            CCITT    KERMIT    ARC    BINHEX    */
> /* the poly:                0x1021    0x8408    0xA001    0x1021    */
> /* original:                0x1021    0x1021    0x8005    0x1021    */
> /* init value:                -1    0    0    0    */
> /* swapped:                no    yes    yes    no    */
> /* bits in CRC:                16    16    16    16    */
> /* ARC used by LHARC, ZOO, STUFFIT                    */
> /* BINHEX used by XMODEM, PACKIT                    */
>
> /* 32 bit crc's */
> /* Value used by:            CCITT32        ZIP        */
> /* the poly:                0x04c11db7    0xedb88320    */
> /* original:                0x04c11db7    0x04c11db7    */
> /* init value:                -1        -1        */
> /* swapped                no        yes        */
> /* bits in CRC:                32        32        */
> /* ZIP used by COMPACTOR                        */
>
> #include <stdio.h>
>
> extern void exit();
> extern char *strcat();
>
> static void initcrctab();
>
> main()
> {
>    initcrctab("ccitt", 0x1021, 0xffff, 0, 16);
>    initcrctab("kermit", 0x8408, 0, 1, 16);
>    initcrctab("arc", 0xa001, 0, 1, 16);
>    initcrctab("binhex", 0x1021, 0, 0, 16);
>    initcrctab("ccitt32",0x04c11db7,0xffffffff,0,32);
>    initcrctab("zip",0xedb88320,0xffffffff,1,32);
>    exit(0);
>    /*NOTREACHED*/
> }
>
> static void initcrctab(name, poly, init, swapped, bits)
> char *name;
> int poly, init, swapped, bits;
> {
>    register  int b, i;
>    unsigned short v;
>    unsigned long vv;
>    FILE *fd;
>    char buf[20];
>      buf[0] = 0;
>    (void)strcat(buf, name);
>    (void)strcat(buf, ".c");
>    if((fd = fopen(buf, "w")) == NULL) {
>    (void)fprintf(stderr, "Cannot open %s for writing\n", buf);
>    exit(1);
>    }
>    (void)fprintf(fd, "unsigned long %s_crcinit = %d;\n", name, init);
>    (void)fprintf(fd, "\n");
>    if(bits == 16) {
>    (void)fprintf(fd, "static unsigned short crctab[256] = {\n");
>    } else {
>    (void)fprintf(fd, "static unsigned long crctab[256] = {\n");
>    }
>    (void)fprintf(fd, "    ");
>    if(bits == 16) {
>    for(b = 0; b < 256; ++b) {
>        if(swapped) {
>        for(v = b, i = 8; --i >= 0;)
>            v = v & 1 ? (v>>1)^poly : v>>1;
>        } else {
>        for(v = b<<8, i = 8; --i >= 0;)
>            v = v & 0x8000 ? (v<<1)^poly : v<<1;
>        }
>        (void)fprintf(fd, "0x%.4x,", v & 0xffff);
>        if((b&7) == 7) {
>        (void)fprintf(fd, "\n");
>        if(b != 255) (void)fprintf(fd, "    ");
>        } else {
>        (void)fprintf(fd, " ");
>        }
>    }
>    } else {
>    for(b = 0; b < 256; ++b) {
>        if(swapped) {
>        for(vv = b, i = 8; --i >= 0;)
>            vv = vv & 1 ? (vv>>1)^poly : vv>>1;
>        } else {
>        for(vv = b<<24, i = 8; --i >= 0;)
>            vv = vv & 0x80000000 ? (vv<<1)^poly : vv<<1;
>        }
>        (void)fprintf(fd, "0x%.8x,", vv & 0xffffffff);
>        if((b&3) == 3) {
>        (void)fprintf(fd, "\n");
>        if(b != 255) (void)fprintf(fd, "    ");
>        } else {
>        (void)fprintf(fd, " ");
>        }
>    }
>    }
>    (void)fprintf(fd, "};\n");
>    (void)fprintf(fd, "\n");
>    (void)fprintf(fd, "unsigned long %s_updcrc(icrc, icp, icnt)\n", name);
>    (void)fprintf(fd, "    unsigned long icrc;\n");
>    (void)fprintf(fd, "    unsigned char *icp;\n");
>    (void)fprintf(fd, "    int icnt;\n");
>    (void)fprintf(fd, "{\n");
>    if(bits == 16) {
>    (void)fprintf(fd, "#define M1 0xff\n");
>    (void)fprintf(fd, "#define M2 0xff00\n");
>    } else {
>    (void)fprintf(fd, "#define M1 0xffffff\n");
>    (void)fprintf(fd, "#define M2 0xffffff00\n");
>    }
>    (void)fprintf(fd, "    register unsigned long crc = icrc;\n");
>    (void)fprintf(fd, "    register unsigned char *cp = icp;\n");
>    (void)fprintf(fd, "    register int cnt = icnt;\n");
>    (void)fprintf(fd, "\n");
>    (void)fprintf(fd, "    while(cnt--) {\n");
>    if(bits == 16) {
>    if (swapped) {
>        (void)fprintf(fd,
>            "\tcrc=((crc>>8)&M1)^crctab[(crc&0xff)^*cp++];\n");
>    } else {
>        (void)fprintf(fd,
>            "\tcrc=((crc<<8)&M2)^crctab[((crc>>8)&0xff)^*cp++];\n");
>    }
>    } else {
>    if(swapped) {
>        (void)fprintf(fd,
>            "\tcrc=((crc>>8)&M1)^crctab[(crc&0xff)^*cp++];\n");
>    } else {
>        (void)fprintf(fd,
>            "\tcrc=((crc<<8)&M2)^crctab[((crc>>24)&0xff)^*cp++];\n");
>    }
>    }
>    (void)fprintf(fd, "    }\n");
>    (void)fprintf(fd, "\n");
>    (void)fprintf(fd, "    return(crc);\n");
>    (void)fprintf(fd, "}\n");
>    (void)fprintf(fd, "\n");
>    (void)fclose(fd);
> }
>
>