-void print_result(char *name, uint8_t *buf, size_t len);
-size_t nbytes(size_t nbits);
-uint32_t SwapBits(uint32_t value, int nrbits);
-void num_to_bytes(uint64_t n, size_t len, uint8_t* dest);
-uint64_t bytes_to_num(uint8_t* src, size_t len);
-void rol(uint8_t *data, const size_t len);
-void lsl (uint8_t *data, size_t len);
-
-void LED(int led, int ms);
-void LEDsoff();
-void LEDson();
-void LEDsinvert();
-int BUTTON_CLICKED(int ms);
-int BUTTON_HELD(int ms);
-void FormatVersionInformation(char *dst, int len, const char *prefix, void *version_information);
+extern void print_result(char *name, uint8_t *buf, size_t len);
+extern size_t nbytes(size_t nbits);
+extern uint32_t SwapBits(uint32_t value, int nrbits);
+extern void num_to_bytes(uint64_t n, size_t len, uint8_t* dest);
+extern uint64_t bytes_to_num(uint8_t* src, size_t len);
+extern void rol(uint8_t *data, const size_t len);
+extern void lsl (uint8_t *data, size_t len);
+
+extern void LED(int led, int ms);
+extern void LEDsoff();
+extern void LEDson();
+extern void LEDsinvert();
+extern int BUTTON_CLICKED(int ms);
+extern int BUTTON_HELD(int ms);
+extern void FormatVersionInformation(char *dst, int len, const char *prefix, void *version_information);