diff --git a/controller_teensy/src/main.cpp b/controller_teensy/src/main.cpp
index 6b456aa..5a4309e 100644
--- a/controller_teensy/src/main.cpp
+++ b/controller_teensy/src/main.cpp
@@ -418,9 +418,19 @@ void readADC() {
 
   
   if (digitalRead(PIN_MODE_SWITCH)) { //pushed in, also high if cable got disconnected
-    speedmode=SPEEDMODE_SLOW;
+    if (speedmode!=SPEEDMODE_SLOW) {
+      speedmode=SPEEDMODE_SLOW;
+      if (loopmillis>WRITE_HEADER_TIME) {
+        writeLogComment(Serial1,loopmillis, "Mode switched to SPEEDMODE_SLOW");
+      }
+    }
   }else{ //button not pushed in
-    speedmode=SPEEDMODE_NORMAL;
+    if (speedmode!=SPEEDMODE_NORMAL) {
+      speedmode=SPEEDMODE_NORMAL;
+      if (loopmillis>WRITE_HEADER_TIME) {
+        writeLogComment(Serial1,loopmillis, "Mode switched to SPEEDMODE_NORMAL");
+      }
+    }
   }