msp430fr413x_CRC.c

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//******************************************************************************
//   MSP430FR413x Demo - CRC16, Compare CRC output with software-based algorithm
//
//   Description: An array of 16 random 16-bit values are moved through the CRC
//   module, as well as a software-based CRC-CCIT-BR algorithm. Due to the fact
//   that the software-based algorithm handles 8-bit inputs only, the 16-bit
//   words are broken into two 8-bit words before being run through (lower byte
//   first). The outputs of both methods are then compared to ensure that the
//   operation of the CRC module is consistent with the expected outcome. If
//   the values of each output are equal, set P1.0, else reset.
//
//   ACLK = default REFO ~32768Hz, MCLK = SMCLK = default DCODIV ~1MHz.
//
//                MSP430FR4133
//             -----------------
//         /|\|                 |
//          | |                 |
//          --|RST              |
//            |                 |
//            |             P1.0|--> LED
//
//   Cen Fang
//   Texas Instruments Inc.
//   June 2013
//   Built with IAR Embedded Workbench v5.60 & Code Composer Studio v5.5
//******************************************************************************
#include <msp430.h>

unsigned int CRC_Init = 0xFFFF;
unsigned int i;
unsigned int CRC_Input[]= {0x0fc0, 0x1096, 0x5042, 0x0010,  // 16 random 16-bit numbers
                           0x7ff7, 0xf86a, 0xb58e, 0x7651,  // these numbers can be
                           0x8b88, 0x0679, 0x0123, 0x9599,  // modified if desired
                           0xc58c, 0xd1e2, 0xe144, 0xb691 };
unsigned int CRC_Results;
unsigned int SW_Results;
unsigned int CRC_New;

// Software Algorithm Function Definition
unsigned int CCITT_Update(unsigned int, unsigned int);

int main(void)
{
    WDTCTL = WDTPW | WDTHOLD;               // Stop watchdog timer

    P1OUT &= ~BIT0;                         // Clear P1.0 output state
    P1DIR |= BIT0;                          // Set P1.0 to output direction

    PM5CTL0 &= ~LOCKLPM5;                   // Disable the GPIO power-on default high-impedance mode
                                            // to activate previously configured port settings

    // Init CRC
    CRCINIRES = CRC_Init;                   // Init CRC with 0xFFFF

    for(i=0;i<16;i++)
    {
        // Input random values into CRC Hardware
        CRCDIRB = CRC_Input[i];             // Input data in CRC
        __no_operation();
    }
    CRC_Results = CRCINIRES;                // Save results (per CRC-CCITT standard)

    CRC_New = CRC_Init;                     // Put CRC Init value into CRC_New
    for(i = 0; i < 16; i++)
    {
        // Input values into Software algorithm (requires 8-bit inputs)
        // Clear upper 8 bits to get lower byte
        unsigned int LowByte = (CRC_Input[i] & 0x00FF);
        // Shift right 8 bits to get upper byte
        unsigned int UpByte = (CRC_Input[i] >> 8);
        // First input lower byte
        CRC_New = CCITT_Update(CRC_New,LowByte);
        // Then input upper byte
        CRC_New = CCITT_Update(CRC_New,UpByte);
    }
    SW_Results = CRC_New;

    // Compare data output results
    if(CRC_Results==SW_Results)             // if data is equal
        P1OUT |= BIT0;                      // set the LED
    else
        P1OUT &= ~BIT0;                     // if not, clear LED

    while(1);                               // infinite loop
}

// Software algorithm - CCITT CRC16 code
unsigned int CCITT_Update(unsigned int init, unsigned int input)
{
    unsigned int CCITT;
    CCITT =(unsigned char)(init >> 8)|(init << 8);
    CCITT ^= input;
    CCITT ^= (unsigned char)(CCITT & 0xFF) >> 4;
    CCITT ^= (CCITT << 8) << 4;
    CCITT ^= ((CCITT & 0xFF) << 4) << 1;
    return CCITT;
}