diff --git a/src/usart/usart.c b/src/usart/usart.c
index 6ea7109..896adc0 100644
--- a/src/usart/usart.c
+++ b/src/usart/usart.c
@@ -9,7 +9,7 @@
 #include <avr/io.h>
 #include <string.h>
 
-
+#define F_CPU 3333333UL
 #define F_PER F_CPU / 6
 #define USART0_BAUD_RATE(BAUD_RATE) ((float)(F_PER * 64 / (16 * (float)BAUD_RATE)) + 0.5)