ms5837 0.2.1

A driver for the MS5837 pressure/temperature sensor from Texas Instruments.
Documentation 
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#include <stdint.h>
// This implementation is slightly modified from the datasheet to used fixed
// width types.

// n_prom defined as 8x unsigned int (n_prom[8])
unsigned char crc4(uint16_t n_prom[]) {
  int cnt;                 // simple counter
  unsigned int n_rem = 0;  // crc remainder
  unsigned char n_bit;
  n_prom[0] = ((n_prom[0]) & 0x0FFF);  // CRC byte is replaced by 0
  n_prom[7] = 0;                       // Subsidiary value, set to 0
                                       // operation is performed on bytes
  for (cnt = 0; cnt < 16; cnt++) {
    // choose LSB or MSB
    if (cnt % 2 == 1)
      n_rem ^= (unsigned short)((n_prom[cnt >> 1]) & 0x00FF);
    else
      n_rem ^= (unsigned short)(n_prom[cnt >> 1] >> 8);
    for (n_bit = 8; n_bit > 0; n_bit--) {
      if (n_rem & (0x8000))
        n_rem = (n_rem << 1) ^ 0x3000;
      else
        n_rem = (n_rem << 1);
    }
  }
  // final 4-bit remainder is CRC code
  n_rem = ((n_rem >> 12) & 0x000F);
  return (n_rem ^ 0x00);
}