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50 lines
1.5 KiB
C
50 lines
1.5 KiB
C
/**
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* Various utility functions for use by device drivers
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*
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* Copyright (C) 2015 Tommy Vestermark
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*/
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#ifndef INCLUDE_UTIL_H_
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#define INCLUDE_UTIL_H_
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#include <stdint.h>
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#include <time.h>
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// Helper macros
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#define max(a,b) ((a) > (b) ? (a) : (b))
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#define min(a,b) ((a) < (b) ? (a) : (b))
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/// Generic Cyclic Redundancy Check CRC-8
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///
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/// Example polynomial: 0x31 = x8 + x5 + x4 + 1 (x8 is implicit)
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/// Example polynomial: 0x80 = x8 + x7 (a normal bit-by-bit parity XOR)
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///
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/// @param message[]: array of bytes to check
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/// @param nBytes: number of bytes in message
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/// @param polynomial: byte is from x^7 to x^0 (x^8 is implicitly one)
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/// @return CRC value
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uint8_t crc8(uint8_t const message[], unsigned nBytes, uint8_t polynomial);
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// buffer to hold localized timestamp YYYY-MM-DD HH:MM:SS
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#define LOCAL_TIME_BUFLEN 32
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/// Printable timestamp in local time
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///
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/// @param time_secs: 0 for now, or seconds since the epoch
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/// @param buf: output buffer, long enough for YYYY-MM-DD HH:MM:SS
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void local_time_str(time_t time_secs, char *buf);
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/**
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* convert unit from celsius to fahrenheit
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* @param celsius input temperature in Celsius
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* @return temperature value in Fahrenheit
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*/
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float celsius2fahrenheit(float celsius);
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#endif /* INCLUDE_UTIL_H_ */
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