-register uint8_t bypass asm("r2");
-register uint8_t done asm("r3");
-register uint8_t portval asm("r4");
-register uint8_t rxidx asm("r5");
+static volatile uint8_t bypass;
+static volatile uint8_t done;
+static volatile uint8_t portval;
+static volatile uint8_t rxidx;
+
+#define BYPASS_ENABLE 14
+#define BYPASS_DISABLE 15