diff --git a/analog.c b/analog.c
index e618e19..2d1478e 100644
--- a/analog.c
+++ b/analog.c
@@ -1,5 +1,7 @@
 #include "analog.h"
 
+#include	"arduino.h"
+
 void analog_init() {
 	PRR &= ~MASK(PRADC);
 	ADMUX = REFERENCE;
diff --git a/analog.h b/analog.h
index 49bc7b5..10e2f93 100644
--- a/analog.h
+++ b/analog.h
@@ -1,10 +1,14 @@
 #ifndef	_ANALOG_H
 #define	_ANALOG_H
 
+#include	<stdint.h>
+
 #define	REFERENCE_AREF	0
 #define	REFERENCE_AVCC	64
 #define	REFERENCE_1V1		192
 
+#include	"machine.h"
+
 #ifndef	REFERENCE
 #warning	define REFERENCE as one of
 #warning	REFERENCE_AREF, REFERENCE_AVCC or REFERENCE_1V1
@@ -12,7 +16,7 @@
 #error REFERENCE undefined
 #endif
 
-void 			analog_init();
+void 			analog_init(void);
 uint16_t	analog_read(uint8_t channel);
 
 #endif	/* _ANALOG_H */
diff --git a/machine.h b/machine.h
index 067391e..13ff441 100644
--- a/machine.h
+++ b/machine.h
@@ -70,4 +70,8 @@
 */
 #define	MOVEBUFFER_SIZE	8
 
+/*
+*/
+#define	REFERENCE	REFERENCE_AREF
+
 #endif	/* _MACHINE_H */