101 lines
3.6 KiB
C
101 lines
3.6 KiB
C
/**
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* This software is subject to the ANT+ Shared Source License
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* www.thisisant.com/swlicenses
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* Copyright (c) Garmin Canada Inc. 2012
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or
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* without modification, are permitted provided that the following
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* conditions are met:
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*
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* 1) Redistributions of source code must retain the above
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* copyright notice, this list of conditions and the following
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* disclaimer.
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*
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* 2) Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials
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* provided with the distribution.
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*
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* 3) Neither the name of Garmin nor the names of its
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* contributors may be used to endorse or promote products
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* derived from this software without specific prior
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* written permission.
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*
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* The following actions are prohibited:
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*
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* 1) Redistribution of source code containing the ANT+ Network
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* Key. The ANT+ Network Key is available to ANT+ Adopters.
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* Please refer to http://thisisant.com to become an ANT+
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* Adopter and access the key.
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*
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* 2) Reverse engineering, decompilation, and/or disassembly of
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* software provided in binary form under this license.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE HEREBY
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES(INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; DAMAGE TO ANY DEVICE, LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
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* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE. SOME STATES DO NOT ALLOW
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* THE EXCLUSION OF INCIDENTAL OR CONSEQUENTIAL DAMAGES, SO THE
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* ABOVE LIMITATIONS MAY NOT APPLY TO YOU.
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*
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*/
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#include "crc.h"
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#include "compiler_abstraction.h"
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/**@brief Function for updating the current CRC-16 value for a single byte input.
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*
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* @param[in] current_crc The current calculated CRC-16 value.
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* @param[in] byte The input data byte for the computation.
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*
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* @return The updated CRC-16 value, based on the input supplied.
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*/
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static __INLINE uint16_t crc16_get(uint16_t current_crc, uint8_t byte)
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{
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static const uint16_t crc16_table[16] =
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{
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0x0000, 0xCC01, 0xD801, 0x1400, 0xF001, 0x3C00, 0x2800, 0xE401,
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0xA001, 0x6C00, 0x7800, 0xB401, 0x5000, 0x9C01, 0x8801, 0x4400
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};
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uint16_t temp;
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// Compute checksum of lower four bits of a byte.
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temp = crc16_table[current_crc & 0xF];
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current_crc = (current_crc >> 4u) & 0x0FFFu;
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current_crc = current_crc ^ temp ^ crc16_table[byte & 0xF];
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// Now compute checksum of upper four bits of a byte.
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temp = crc16_table[current_crc & 0xF];
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current_crc = (current_crc >> 4u) & 0x0FFFu;
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current_crc = current_crc ^ temp ^ crc16_table[(byte >> 4u) & 0xF];
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return current_crc;
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}
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uint16_t crc_crc16_update(uint16_t current_crc, const volatile void * p_data, uint32_t size)
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{
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uint8_t * p_block = (uint8_t *)p_data;
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while (size != 0)
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{
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current_crc = crc16_get(current_crc, *p_block);
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p_block++;
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size--;
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}
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return current_crc;
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}
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