diff --git a/test/DueSerialTest/src/main.cpp b/test/DueSerialTest/src/main.cpp
index 56b48cc..2fbed5f 100644
--- a/test/DueSerialTest/src/main.cpp
+++ b/test/DueSerialTest/src/main.cpp
@@ -43,10 +43,13 @@ void loop() {
   // send data only when you receive data:
   if (SEND_MODE == SendModes::ONLY_WRITE or SEND_MODE == SendModes::WRITE_READ) {
     Serial.println("Sending string..");
+    Serial1.write(STRINGS[STRING_IDX].c_str());
     if(STRING_MODE == StringModes::VARIABLE) {
       STRING_IDX += 1;
+      if(STRING_IDX > 3) {
+        STRING_IDX = 0;
+      }
     }
-    Serial1.write(STRINGS[STRING_IDX].c_str());
   }
   if(
     SEND_MODE == SendModes::WRITE_READ or