AVR Freaks

yes awneil. i gone through it but not getting.

And also i read the http://www.barrgroup.com/Embedded-Systems/How-To/CRC-Calculation-C-Code

And i tried this also.

/*****************************************************
This program was produced by the
CodeWizardAVR V2.05.3 Standard
Automatic Program Generator
© Copyright 1998-2011 Pavel Haiduc, HP InfoTech s.r.l.
http://www.hpinfotech.com

Project :
Version :
Date    : 4/9/2015
Author  : Dev6
Company : sass
Comments:


Chip type               : ATmega128
Program type            : Application
AVR Core Clock frequency: 14.745600 MHz
Memory model            : Small
External RAM size       : 0
Data Stack size         : 1024
*****************************************************/

#include <mega128.h>
#include <stdio.h>
#include <string.h>



#define WIDTH  16    //(8 * sizeof(unsigned char))
#define TOPBIT (1 << (WIDTH - 1))
#define POLYNOMIAL 0x8005

unsigned char crcTable[256];

#ifndef RXB8
#define RXB8 1
#endif

#ifndef TXB8
#define TXB8 0
#endif

#ifndef UPE
#define UPE 2
#endif

#ifndef DOR
#define DOR 3
#endif

#ifndef FE
#define FE 4
#endif

#ifndef UDRE
#define UDRE 5
#endif

#ifndef RXC
#define RXC 7
#endif

#define FRAMING_ERROR (1<<FE)
#define PARITY_ERROR (1<<UPE)
#define DATA_OVERRUN (1<<DOR)
#define DATA_REGISTER_EMPTY (1<<UDRE)
#define RX_COMPLETE (1<<RXC)

// USART0 Receiver buffer
#define RX_BUFFER_SIZE0 256
char rx_buffer0[RX_BUFFER_SIZE0];

#if RX_BUFFER_SIZE0 <= 256
unsigned char rx_wr_index0,rx_rd_index0,rx_counter0;
#else
unsigned int rx_wr_index0,rx_rd_index0,rx_counter0;
#endif

// This flag is set on USART0 Receiver buffer overflow
bit rx_buffer_overflow0;

// USART0 Receiver interrupt service routine
interrupt [USART0_RXC] void usart0_rx_isr(void)
{
char status,data;
status=UCSR0A;
data=UDR0;
if ((status & (FRAMING_ERROR | PARITY_ERROR | DATA_OVERRUN))==0)
   {
   rx_buffer0[rx_wr_index0++]=data;
#if RX_BUFFER_SIZE0 == 256
   // special case for receiver buffer size=256
   if (++rx_counter0 == 0) rx_buffer_overflow0=1;
#else
   if (rx_wr_index0 == RX_BUFFER_SIZE0) rx_wr_index0=0;
   if (++rx_counter0 == RX_BUFFER_SIZE0)
      {
      rx_counter0=0;
      rx_buffer_overflow0=1;
      }
#endif
   }
}

#ifndef _DEBUG_TERMINAL_IO_
// Get a character from the USART0 Receiver buffer
#define _ALTERNATE_GETCHAR_
#pragma used+
char getchar(void)
{
char data;
while (rx_counter0==0);
data=rx_buffer0[rx_rd_index0++];
#if RX_BUFFER_SIZE0 != 256
if (rx_rd_index0 == RX_BUFFER_SIZE0) rx_rd_index0=0;
#endif
#asm("cli")
--rx_counter0;
#asm("sei")
return data;
}
#pragma used-
#endif



void crcInit(void)
{
    unsigned int  remainder;
    unsigned int dividend = 0;
    unsigned char b;

    printf("\nwidth: %d", WIDTH);
    /*
     * Compute the remainder of each possible dividend.
     */
    for (dividend = 0; dividend < 256; ++dividend)
    {
        /*
         * Start with the dividend followed by zeros.
         */
        remainder = dividend << (WIDTH - 8);

        /*
         * Perform modulo-2 division, a bit at a time.
         */
        for (b = 8; b > 0; --b)
        {
            /*
             * Try to divide the current data bit.
             */
            if (remainder & TOPBIT)
            {
                remainder = (remainder << 1) ^ POLYNOMIAL;
            }
            else
            {
                remainder = (remainder << 1);
            }
        }

        /*
         * Store the result into the table.
         */
        crcTable[dividend] = remainder;
    }

}   /* crcInit() */

unsigned char crcFast(unsigned char const message[], unsigned int nBytes)
{
    unsigned char data;
    unsigned char remainder = 0;
    unsigned int byte = 0;


    /*
     * Divide the message by the polynomial, a byte at a time.
     */
    for (byte = 0; byte < nBytes; ++byte)
    {
        data = message[byte] ^ (remainder >> (WIDTH - 8));
        remainder = crcTable[data] ^ (remainder << 8);
    }

    printf("\nremainder: 0x%X", remainder);

    /*
     * The final remainder is the CRC.
     */
    return (remainder);

}   /* crcFast() */

void main(void)
{
// Declare your local variables here

unsigned char checksum;
unsigned char arr[] = "123456789";

// Input/Output Ports initialization
// Port A initialization
// Func7=In Func6=In Func5=In Func4=In Func3=In Func2=In Func1=In Func0=In
// State7=T State6=T State5=T State4=T State3=T State2=T State1=T State0=T
PORTA=0x00;
DDRA=0x00;

// Port B initialization
// Func7=In Func6=In Func5=In Func4=In Func3=In Func2=In Func1=In Func0=In
// State7=T State6=T State5=T State4=T State3=T State2=T State1=T State0=T
PORTB=0x00;
DDRB=0x00;

// Port C initialization
// Func7=In Func6=In Func5=In Func4=In Func3=In Func2=In Func1=In Func0=In
// State7=T State6=T State5=T State4=T State3=T State2=T State1=T State0=T
PORTC=0x00;
DDRC=0x00;

// Port D initialization
// Func7=In Func6=In Func5=In Func4=In Func3=In Func2=In Func1=In Func0=In
// State7=T State6=T State5=T State4=T State3=T State2=T State1=T State0=T
PORTD=0x00;
DDRD=0x00;

// Port E initialization
// Func7=In Func6=In Func5=In Func4=In Func3=In Func2=In Func1=In Func0=In
// State7=T State6=T State5=T State4=T State3=T State2=T State1=T State0=T
PORTE=0x00;
DDRE=0x00;

// Port F initialization
// Func7=In Func6=In Func5=In Func4=In Func3=In Func2=In Func1=In Func0=In
// State7=T State6=T State5=T State4=T State3=T State2=T State1=T State0=T
PORTF=0x00;
DDRF=0x00;

// Port G initialization
// Func4=In Func3=In Func2=In Func1=In Func0=In
// State4=T State3=T State2=T State1=T State0=T
PORTG=0x00;
DDRG=0x00;

// USART0 initialization
// Communication Parameters: 8 Data, 1 Stop, No Parity
// USART0 Receiver: On
// USART0 Transmitter: On
// USART0 Mode: Asynchronous
// USART0 Baud Rate: 9600
UCSR0A=0x00;
UCSR0B=0x98;
UCSR0C=0x06;
UBRR0H=0x00;
UBRR0L=0x5F;

// Global enable interrupts
#asm("sei")

puts("\nStart");

crcInit();

checksum = crcFast(arr, strlen(arr));
printf("\nl: %d", strlen(arr));
//printf("\nlength: %d", sizeof(arr));
printf("\nchecksum: 0x%X", checksum);

puts("\nEnd");

while (1)
      {
      // Place your code here

      }
}

output is:

 Start

                                                     width: 16
                                                              remainder: 0x96
                                                                             l:
9
 checksum: 0x96
               End

Thanks a lot clawson. I tried your code.

In this for 0xA001 output is  0x4b37

for 0x8005  output is 0x3d7b

not getting the expected value

Okay clawson. Thanks  a lot for great help :)

hi clawson,

   in OP  code i changed polynomial value as 0xA001 and initial crc as 0x0000 and now i am getting the result as 0xBB3D.

But in online calculator the used polynomial value as 0x8005 for this 0x8005 polynomial result is 0xBB3D. i am getting confusing which one is correct.

yes it is okay. why it should be like that.  really i am getting confused why it is reversed.  please 

yes okay. Thanks a lot. i will google it.

Yes jerry. i have downloaded the zip file. in that .exe is not running.

Hai clawson, 

    Good day! very very sorry for troubles. now i edited the post.