34 lines
680 B
C
34 lines
680 B
C
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/**
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Copyright (c) 2017, Łukasz Marcin Podkalicki <lpodkalicki@gmail.com>
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Lightweight library of 16 bit random number generator based on LFSR.
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*/
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#include <avr/eeprom.h>
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#include "random_avr.h"
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static uint16_t random_number = 0;
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static uint16_t
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lfsr16_next(uint16_t n)
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{
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return (n >> 0x01U) ^ (-(n & 0x01U) & 0xB400U);
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}
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void random_init(uint16_t seed)
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{
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#ifdef USE_RANDOM_SEED
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random_number = lfsr16_next(eeprom_read_word((uint16_t *)RANDOM_SEED_ADDRESS) ^ seed);
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eeprom_write_word((uint16_t *)0, random_number);
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#else
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random_number = seed;
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#endif /* !USE_RANDOM_SEED */
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}
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uint16_t
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random_avr(void)
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{
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return (random_number = lfsr16_next(random_number));
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}
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