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57 lines
1.8 KiB
57 lines
1.8 KiB
/******************************************************************************
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*
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* Copyright (C) 2018 ST Microelectronics S.A.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*
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******************************************************************************/
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#include "Iso13239CRC.h"
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//************************************ Functions *******************************
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/*******************************************************************************
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**
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** Function computeCrc
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**
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** Description Computes the 16-bit CRC of the specified function.
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**
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** Parameters data - data to compute the CRC over.
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** len - data length.
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**
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** Returns CRC of the data. -1 if something went wrong.
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**
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*******************************************************************************/
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uint16_t computeCrc(uint8_t *data, int len) {
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uint16_t tempCrc;
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tempCrc = (unsigned short)CRC_PRESET;
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int i, k;
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for (i = 0; i < len; i++) {
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tempCrc = tempCrc ^ ((unsigned short)data[i]);
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for (k = 0; k < 8; k++) {
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if ((tempCrc & 0x0001) == 0x0001) {
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tempCrc = (tempCrc >> 1) ^ CRC_POLYNOMIAL;
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} else {
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tempCrc = tempCrc >> 1;
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}
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}
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}
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tempCrc = ~tempCrc;
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data[len] = (uint8_t)tempCrc;
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data[len + 1] = (uint8_t)(tempCrc >> 8);
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return tempCrc;
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}
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