Version 1

code/random_avr.c

@@ -0,0 +1,33 @@
+/**
+   Copyright (c) 2017, Łukasz Marcin Podkalicki <lpodkalicki@gmail.com>
+   Lightweight library of 16 bit random number generator based on LFSR.
+*/
+
+#include <avr/eeprom.h>
+#include "random_avr.h"
+
+static uint16_t random_number = 0;
+
+static uint16_t
+lfsr16_next(uint16_t n)
+{
+
+  return (n >> 0x01U) ^ (-(n & 0x01U) & 0xB400U);
+}
+
+void random_init(uint16_t seed)
+{
+#ifdef USE_RANDOM_SEED
+  random_number = lfsr16_next(eeprom_read_word((uint16_t *)RANDOM_SEED_ADDRESS) ^ seed);
+  eeprom_write_word((uint16_t *)0, random_number);
+#else
+  random_number = seed;
+#endif /* !USE_RANDOM_SEED */
+}
+
+uint16_t
+random_avr(void)
+{
+
+  return (random_number = lfsr16_next(random_number));
+}