diff --git a/fw/sweep.c b/fw/sweep.c
index 1f98f77..4bc3e15 100644
--- a/fw/sweep.c
+++ b/fw/sweep.c
@@ -70,9 +70,7 @@ ISR(TIMER1_OVF_vect)
 
 	/* output the next line */
 
-	PORTB = (PORTB & 0x3f) | (curr_line->cb & 0xc0);
-	PORTC = curr_line->cb;
-	PORTD = curr_line->d;
+	set_line(*curr_line);
 
 	/* move to the next line */
 
diff --git a/fw/sweep.h b/fw/sweep.h
index d9bdcb5..329316c 100644
--- a/fw/sweep.h
+++ b/fw/sweep.h
@@ -17,6 +17,10 @@
 #include <stdbool.h>
 #include <stdint.h>
 
+#include <avr/io.h>
+
+#include "image.h"
+
 
 struct sweep {
 	uint32_t start_ticks;	/* absolute start time */
@@ -29,6 +33,15 @@ struct sweep {
 
 extern volatile bool sweeping;
 
+
+static inline void set_line(struct line line)
+{
+	PORTB = (PORTB & 0x3f) | (line.cb & 0xc0);
+	PORTC = line.cb;
+	PORTD = line.d;
+}
+
+
 uint32_t uptime_irq(void);
 uint32_t uptime(void);