67 lines
1.7 KiB
C
67 lines
1.7 KiB
C
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/****************************************************************************
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* drivers/sensors/msxxxx_crc4.c
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#ifndef __INCLUDE_NUTTX_SENSORS_MSXXXX_CRC4_H
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#define __INCLUDE_NUTTX_SENSORS_MSXXXX_CRC4_H
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/****************************************************************************
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* Public Function Prototypes
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****************************************************************************/
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/****************************************************************************
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* Name: ms58xx_crc
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*
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* Description:
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* Calculate the CRC.
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*
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****************************************************************************/
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static uint8_t msxxxx_crc4(FAR uint16_t *src,
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uint8_t crcndx,
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uint16_t crcmask)
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{
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uint16_t cnt;
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uint16_t n_rem;
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uint16_t crc_read;
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uint8_t n_bit;
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n_rem = 0x00;
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crc_read = src[crcndx];
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src[crcndx] &= ~crcmask;
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for (cnt = 0; cnt < 16; cnt++)
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{
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if (cnt % 2 == 1)
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{
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n_rem ^= src[cnt >> 1] & 0x00ff;
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}
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else
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{
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n_rem ^= src[cnt >> 1] >> 8;
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}
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for (n_bit = 8; n_bit > 0; n_bit--)
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{
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if (n_rem & (0x8000) != 0)
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{
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n_rem = (n_rem << 1) ^ 0x3000;
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}
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else
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{
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n_rem <<= 1;
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}
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}
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}
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n_rem = (n_rem >> 12) & 0x000f;
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src[crcndx] = crc_read;
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return n_rem ^ 0x00;
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}
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#endif /* __INCLUDE_NUTTX_SENSORS_MSXXXX_CRC4_H */
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