diff --git a/main.c b/main.c
index 442a1e5..13d8e81 100644
--- a/main.c
+++ b/main.c
@@ -4,10 +4,12 @@
  */
 #include <stdint.h>
 #include <stdbool.h>
-#include "stm8s.h"
+#include <stdlib.h>
+
+#include "stm8s.h"
+#include "main.h"
+
 
-// get length of array
-#define ARRAY_LENGTH(x) (sizeof(x) / sizeof((x)[0]))
 
 // blocking wait (in 10 us steps, up to UINT32_MAX / 10)
 static void wait_10us(uint32_t us10)
diff --git a/main.h b/main.h
new file mode 100644
index 0000000..f3ea966
--- /dev/null
+++ b/main.h
@@ -0,0 +1,2 @@
+// get length of array
+#define ARRAY_LENGTH(x) (sizeof(x) / sizeof((x)[0]))