added test macro in readme

README.md

@@ -79,3 +79,38 @@ avrdude: safemode: Fuses OK (E:00, H:00, L:00)
 
 avrdude done.  Thank you.
 ```
+
+## test macros
+
+#include <stdio.h>
+#include <avr/io.h>
+
+// // stringify
+#define STRINGIFY_HELPER(x) #x
+#define STRINGIFY(x) STRINGIFY_HELPER(x)
+
+#define CONCAT_HELPER(x, y) x ## y
+#define CONCAT(x, y) CONCAT_HELPER(x, y)
+
+// get argument at nth position
+#define ARG_1(v1, v2) v1
+#define ARG_2(v1, v2) v2
+#define GET_PORT(args) ARG_1 args
+#define GET_BIT(args) ARG_2 args
+
+// actions on registers
+#define SET(register, bit) register |= 1 << bit
+
+// actions on ports
+#define MODE_OUTPUT(elem) SET(CONCAT(DDR, GET_PORT(elem)), GET_BIT(elem))
+
+// elements
+#define LED1 (B, 0)
+
+int main()
+{
+MODE_OUTPUT(LED1);
+
+    return 0;
+
+}