extern char getchar(void);
extern void ao_avr_stdio_init(void);
-extern const uint16_t ao_serial_number;
+#define AO_ROMCONFIG_VERSION 2
+
+#define AO_ROMCONFIG_SYMBOL(a) const
+
+extern AO_ROMCONFIG_SYMBOL(0) uint16_t ao_serial_number;
#define AVR_PUSH8(stack, val) (*((stack)--) = (val))