mirror of https://github.com/ARMmbed/mbed-os.git
Martin Kojtal
commit
a15892332f
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@ -0,0 +1,234 @@
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/**********************************************************************
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*
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* Filename: crc.c
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*
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* Description: Slow and fast implementations of the CRC standards.
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*
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* Notes: The parameters for each supported CRC standard are
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* defined in the header file crc.h. The implementations
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* here should stand up to further additions to that list.
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*
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*
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* Copyright (c) 2000 by Michael Barr. This software is placed into
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* the public domain and may be used for any purpose. However, this
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* notice must not be changed or removed and no warranty is either
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* expressed or implied by its publication or distribution.
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**********************************************************************/
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#include "crc.h"
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/*
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* Derive parameters from the standard-specific parameters in crc.h.
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*/
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#define WIDTH (8 * sizeof(crc))
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#define TOPBIT (1 << (WIDTH - 1))
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#if (REFLECT_DATA == TRUE)
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#undef REFLECT_DATA
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#define REFLECT_DATA(X) ((unsigned char) reflect((X), 8))
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#else
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#undef REFLECT_DATA
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#define REFLECT_DATA(X) (X)
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#endif
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#if (REFLECT_REMAINDER == TRUE)
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#undef REFLECT_REMAINDER
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#define REFLECT_REMAINDER(X) ((crc) reflect((X), WIDTH))
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#else
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#undef REFLECT_REMAINDER
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#define REFLECT_REMAINDER(X) (X)
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#endif
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/*********************************************************************
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*
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* Function: reflect()
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*
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* Description: Reorder the bits of a binary sequence, by reflecting
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* them about the middle position.
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*
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* Notes: No checking is done that nBits <= 32.
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*
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* Returns: The reflection of the original data.
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*
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*********************************************************************/
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static unsigned long
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reflect(unsigned long data, unsigned char nBits)
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{
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unsigned long reflection = 0x00000000;
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unsigned char bit;
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/*
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* Reflect the data about the center bit.
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*/
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for (bit = 0; bit < nBits; ++bit)
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{
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/*
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* If the LSB bit is set, set the reflection of it.
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*/
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if (data & 0x01)
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{
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reflection |= (1 << ((nBits - 1) - bit));
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}
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data = (data >> 1);
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}
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return (reflection);
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} /* reflect() */
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/*********************************************************************
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*
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* Function: crcSlow()
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*
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* Description: Compute the CRC of a given message.
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*
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* Notes:
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*
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* Returns: The CRC of the message.
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*
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*********************************************************************/
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crc
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crcSlow(unsigned char const message[], int nBytes)
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{
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crc remainder = INITIAL_REMAINDER;
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int byte;
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unsigned char bit;
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/*
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* Perform modulo-2 division, a byte at a time.
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*/
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for (byte = 0; byte < nBytes; ++byte)
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{
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/*
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* Bring the next byte into the remainder.
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*/
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remainder ^= (REFLECT_DATA(message[byte]) << (WIDTH - 8));
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/*
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* Perform modulo-2 division, a bit at a time.
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*/
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for (bit = 8; bit > 0; --bit)
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{
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/*
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* Try to divide the current data bit.
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*/
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if (remainder & TOPBIT)
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{
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remainder = (remainder << 1) ^ POLYNOMIAL;
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}
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else
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{
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remainder = (remainder << 1);
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}
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}
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}
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/*
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* The final remainder is the CRC result.
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*/
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return (REFLECT_REMAINDER(remainder) ^ FINAL_XOR_VALUE);
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} /* crcSlow() */
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crc crcTable[256];
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/*********************************************************************
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*
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* Function: crcInit()
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*
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* Description: Populate the partial CRC lookup table.
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*
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* Notes: This function must be rerun any time the CRC standard
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* is changed. If desired, it can be run "offline" and
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* the table results stored in an embedded system's ROM.
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*
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* Returns: None defined.
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*
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*********************************************************************/
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void
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crcInit(void)
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{
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crc remainder;
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int dividend;
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unsigned char bit;
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/*
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* Compute the remainder of each possible dividend.
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*/
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for (dividend = 0; dividend < 256; ++dividend)
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{
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/*
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* Start with the dividend followed by zeros.
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*/
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remainder = dividend << (WIDTH - 8);
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/*
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* Perform modulo-2 division, a bit at a time.
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*/
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for (bit = 8; bit > 0; --bit)
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{
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/*
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* Try to divide the current data bit.
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*/
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if (remainder & TOPBIT)
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{
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remainder = (remainder << 1) ^ POLYNOMIAL;
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}
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else
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{
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remainder = (remainder << 1);
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}
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}
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/*
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* Store the result into the table.
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*/
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crcTable[dividend] = remainder;
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}
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} /* crcInit() */
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/*********************************************************************
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*
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* Function: crcFast()
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*
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* Description: Compute the CRC of a given message.
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*
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* Notes: crcInit() must be called first.
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*
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* Returns: The CRC of the message.
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*
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*********************************************************************/
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crc
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crcFast(unsigned char const message[], int nBytes)
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{
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crc remainder = INITIAL_REMAINDER;
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unsigned char data;
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int byte;
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/*
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* Divide the message by the polynomial, a byte at a time.
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*/
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for (byte = 0; byte < nBytes; ++byte)
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{
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data = REFLECT_DATA(message[byte]) ^ (remainder >> (WIDTH - 8));
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remainder = crcTable[data] ^ (remainder << 8);
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}
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/*
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* The final remainder is the CRC.
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*/
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return (REFLECT_REMAINDER(remainder) ^ FINAL_XOR_VALUE);
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} /* crcFast() */
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@ -0,0 +1,77 @@
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/**********************************************************************
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*
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* Filename: crc.h
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*
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* Description: A header file describing the various CRC standards.
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*
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* Notes:
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*
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*
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* Copyright (c) 2000 by Michael Barr. This software is placed into
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* the public domain and may be used for any purpose. However, this
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* notice must not be changed or removed and no warranty is either
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* expressed or implied by its publication or distribution.
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**********************************************************************/
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#ifndef _crc_h
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#define _crc_h
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#define FALSE 0
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#define TRUE !FALSE
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/*
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* Select the CRC standard from the list that follows.
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*/
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#define CRC16
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#if defined(CRC_CCITT)
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typedef unsigned short crc;
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#define CRC_NAME "CRC-CCITT"
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#define POLYNOMIAL 0x1021
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#define INITIAL_REMAINDER 0xFFFF
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#define FINAL_XOR_VALUE 0x0000
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#define REFLECT_DATA FALSE
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#define REFLECT_REMAINDER FALSE
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#define CHECK_VALUE 0x29B1
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#elif defined(CRC16)
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typedef unsigned short crc;
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#define CRC_NAME "CRC-16"
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#define POLYNOMIAL 0x8005
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#define INITIAL_REMAINDER 0x0000
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#define FINAL_XOR_VALUE 0x0000
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#define REFLECT_DATA TRUE
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#define REFLECT_REMAINDER TRUE
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#define CHECK_VALUE 0xBB3D
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#elif defined(CRC32)
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typedef unsigned long crc;
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#define CRC_NAME "CRC-32"
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#define POLYNOMIAL 0x04C11DB7
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#define INITIAL_REMAINDER 0xFFFFFFFF
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#define FINAL_XOR_VALUE 0xFFFFFFFF
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#define REFLECT_DATA TRUE
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#define REFLECT_REMAINDER TRUE
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#define CHECK_VALUE 0xCBF43926
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#else
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#error "One of CRC_CCITT, CRC16, or CRC32 must be #define'd."
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#endif
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void crcInit(void);
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crc crcSlow(unsigned char const message[], int nBytes);
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crc crcFast(unsigned char const message[], int nBytes);
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#endif /* _crc_h */
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@ -15,6 +15,9 @@
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*/
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#include "gpio_api.h"
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#define CRC16
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#include "crc.h"
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// called before main - implement here if board needs it ortherwise, let
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// the application override this if necessary
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//void mbed_sdk_init()
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@ -34,21 +37,36 @@ void NMI_Handler(void)
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// Provide ethernet devices with a semi-unique MAC address from the UUID
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void mbed_mac_address(char *mac)
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{
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// Fetch word 0
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uint32_t word0 = *(uint32_t *)0x40048060;
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// Fetch word 1
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// we only want bottom 16 bits of word1 (MAC bits 32-47)
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// and bit 1 forced to 1, bit 0 forced to 0
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// Locally administered MAC, reduced conflicts
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// http://en.wikipedia.org/wiki/MAC_address
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uint32_t word1 = *(uint32_t *)0x4004805C;
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word1 |= 0x00000002;
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word1 &= 0x0000FFFE;
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mac[0] = (word1 & 0x000000ff);
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mac[1] = (word1 & 0x0000ff00) >> 8;
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mac[2] = (word0 & 0xff000000) >> 24;
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mac[3] = (word0 & 0x00ff0000) >> 16;
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mac[4] = (word0 & 0x0000ff00) >> 8;
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mac[5] = (word0 & 0x000000ff);
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unsigned int UUID_LOC_BASE = 0x40048054; // First adddress of the 4-word UUID
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char uuid[16]; // So we can take a local copy of the UUID
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uint32_t MAC[3]; // 3 16 bits words for the MAC
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// copy the UUID to the variable MAC[]
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memcpy(uuid,(const void*)UUID_LOC_BASE,sizeof(uuid));
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// generate three CRC16's using different slices of the UUID
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MAC[0] = crcSlow(uuid, 8); // most significant half-word
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MAC[1] = crcSlow(uuid, 12);
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MAC[2] = crcSlow(uuid, 16); // least significant half word
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// The network stack expects an array of 6 bytes
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// so we copy, and shift and copy from the half-word array to the byte array
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mac[0] = MAC[0] >> 8;
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mac[1] = MAC[0];
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mac[2] = MAC[1] >> 8;
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mac[3] = MAC[1];
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mac[4] = MAC[2] >> 8;
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mac[5] = MAC[2];
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// We want to force bits [1:0] of the most significant byte [0]
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// to be "10"
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// http://en.wikipedia.org/wiki/MAC_address
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mac[0] |= 0x02; // force bit 1 to a "1" = "Locally Administered"
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mac[0] &= 0xFE; // force bit 0 to a "0" = Unicast
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}
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