provide version with and without ttl decrease

uart.c

@@ -29,8 +29,8 @@ unsigned char BUF_TX[20];
 unsigned char *TX;
 
 TX = &BUF_TX[0];
-*TX++ = 'R'; // -> decrease TTL
-//*TX++ = 'P'; // -> do NOT decrease TTL
+//*TX++ = 'R'; // -> decrease TTL
+*TX++ = 'P'; // -> do NOT decrease TTL
 /*
 *TX++ = 'a';
 *TX++ = 's';