Implement USART with bot RX and TX interrupts

src/common/common.c

@@ -0,0 +1,24 @@
+#include "common.h"
+#include "bus/usart.h"
+#include <stdio.h>
+
+static void Puts(const char *str)
+{
+	while (*str) {
+		USART_Putc(*str++);
+	}
+}
+
+void Info(const char *fmt, ...)
+{
+	va_list ap;
+	char msg[256];
+
+	va_start(ap, fmt);
+	vsnprintf(msg, sizeof(msg), fmt, ap);
+	va_end(ap);
+
+	Puts("[CORE] ");
+	Puts(msg);
+	Puts("\r\n");
+}