83 lines
2.5 KiB
C
83 lines
2.5 KiB
C
/****************************************************************************
|
|
* include/nuttx/sensors/msxxxx_crc4.h
|
|
*
|
|
* Licensed to the Apache Software Foundation (ASF) under one or more
|
|
* contributor license agreements. See the NOTICE file distributed with
|
|
* this work for additional information regarding copyright ownership. The
|
|
* ASF licenses this file to you under the Apache License, Version 2.0 (the
|
|
* "License"); you may not use this file except in compliance with the
|
|
* License. You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
|
|
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
|
|
* License for the specific language governing permissions and limitations
|
|
* under the License.
|
|
*
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Included Files
|
|
****************************************************************************/
|
|
|
|
#ifndef __INCLUDE_NUTTX_SENSORS_MSXXXX_CRC4_H
|
|
#define __INCLUDE_NUTTX_SENSORS_MSXXXX_CRC4_H
|
|
|
|
/****************************************************************************
|
|
* Public Function Prototypes
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Name: ms58xx_crc
|
|
*
|
|
* Description:
|
|
* Calculate the CRC.
|
|
*
|
|
****************************************************************************/
|
|
|
|
static uint8_t msxxxx_crc4(FAR uint16_t *src,
|
|
uint8_t crcndx,
|
|
uint16_t crcmask)
|
|
{
|
|
uint16_t cnt;
|
|
uint16_t n_rem;
|
|
uint16_t crc_read;
|
|
uint8_t n_bit;
|
|
|
|
n_rem = 0x00;
|
|
crc_read = src[crcndx];
|
|
src[crcndx] &= ~crcmask;
|
|
|
|
for (cnt = 0; cnt < 16; cnt++)
|
|
{
|
|
if (cnt % 2 == 1)
|
|
{
|
|
n_rem ^= src[cnt >> 1] & 0x00ff;
|
|
}
|
|
else
|
|
{
|
|
n_rem ^= src[cnt >> 1] >> 8;
|
|
}
|
|
|
|
for (n_bit = 8; n_bit > 0; n_bit--)
|
|
{
|
|
if (n_rem & (0x8000) != 0)
|
|
{
|
|
n_rem = (n_rem << 1) ^ 0x3000;
|
|
}
|
|
else
|
|
{
|
|
n_rem <<= 1;
|
|
}
|
|
}
|
|
}
|
|
|
|
n_rem = (n_rem >> 12) & 0x000f;
|
|
src[crcndx] = crc_read;
|
|
return n_rem ^ 0x00;
|
|
}
|
|
|
|
#endif /* __INCLUDE_NUTTX_SENSORS_MSXXXX_CRC4_H */
|