diff --git a/software/GToE/GToE.ino b/software/GToE/GToE.ino
index 650f248..bca387f 100644
--- a/software/GToE/GToE.ino
+++ b/software/GToE/GToE.ino
@@ -55,6 +55,9 @@ int needToResetChannel;
 bool beatCounted = false;
 bool pulseCounted = false;
 
+int masterClockMode = 0; // 0 - internal, 1 - external 24ppqn
+bool externalPulseCounted = true;
+
 int displayTab = 0;
 int displayTabOld;
 int insideTab = 0;
@@ -86,7 +89,7 @@ void setup() {
   pinMode(ENC_BTN_PIN, INPUT_PULLUP);
   pinMode(START_STOP_BTN_PIN, INPUT_PULLUP);
   pinMode(START_STOP_BTN_PIN, ANALOGUE_INPUT_1_PIN);
-  pinMode(INPUT_PIN, INPUT_PULLUP); //probably will need interrupt
+  pinMode(INPUT_PIN, INPUT_PULLUP);
   attachInterrupt(digitalPinToInterrupt(INPUT_PIN), externalClock, RISING);
 
   for (int i=0; i<6; i++) {
@@ -98,7 +101,7 @@ void setup() {
   updateScreen();
   updateTiming();
 
-  FlexiTimer2::set(1, 1.0/1000, internalClock); // 1.0/1000 = 1ms period
+  FlexiTimer2::set(1, 1.0/1000, clock); // 1.0/1000 = 1ms period
   FlexiTimer2::start();
 }
 
@@ -106,7 +109,7 @@ void loop() {
   checkInputs();
 }
 
-void internalClock() {
+void clock() {
   if (isPlaying) {
 
     // Action on each pulse
@@ -162,13 +165,24 @@ void internalClock() {
       pulseCounted = true;
     }
 
-    //internal pulse
-    if (pulseClockCount == 0) {
-      pulseCount++;
-      beatCounted = false;
-      pulseCounted = false;
-    } 
-    if (pulseClockCount < pulsePeriod) {
+    switch (masterClockMode) {
+      case 0:  //internal
+        if (pulseClockCount == 0) {
+          pulseCount++;
+          beatCounted = false;
+          pulseCounted = false;
+        } 
+        break;
+      case 1: //external 24ppqn
+        if (externalPulseCounted == false) {
+          pulseCount++;
+          externalPulseCounted = true;
+          beatCounted = false;
+          pulseCounted = false;
+        }
+        break;
+    }
+    if (pulseClockCount < pulsePeriod) {  
       pulseClockCount++;
     } else {
       pulseClockCount = 0;
@@ -183,12 +197,11 @@ void internalClock() {
         digitalWrite(outsPins[i], LOW);
       }
     }
-
   }
 }
 
 void externalClock() {
- digitalWrite(outsPins[0], !digitalRead(outsPins[0]));
+  externalPulseCounted = false;
 }
 
 void updateTiming() {
@@ -238,6 +251,14 @@ void checkInputs() {
       }
       updateScreen();
     }
+    else if (encReleasedTime - encPressedTime < 2000 && displayTab == 0) { // switch to external clock mode
+      if (masterClockMode == 0) {
+        masterClockMode = 1;
+      } else {
+        masterClockMode = 0;
+      }
+      updateScreen();
+    }
   }
 
   //encoder
@@ -245,7 +266,7 @@ void checkInputs() {
   int encPosition = encoder.getPosition();
   if (encPositionOld != encPosition) {
     int change = encPositionOld - encPosition;
-    if (displayTab == 0) {
+    if (displayTab == 0 && masterClockMode == 0) {
       bpm = bpm + change;
       if (bpm > MAXBPM) {
         bpm = MAXBPM;
@@ -333,9 +354,11 @@ void updateScreen() {
   display.setCursor(4,16);
   display.setTextSize(3);
   display.setTextColor(SSD1306_WHITE);
-  if (displayTab == 0) {
+  if (displayTab == 0 && masterClockMode == 0) {
     display.print(bpm);
     display.println(F("bpm")); 
+  } else if (displayTab == 0 && masterClockMode != 0) {
+    display.println(F("EXT")); 
   } else {
       if (clockModes[channels[displayTab-1].mode] == 0) {
         display.print(F("OFF"));