diff --git a/CosmicPiV2Simulator.ino b/CosmicPiV2Simulator.ino
index df7dc9d..10d4c23 100644
--- a/CosmicPiV2Simulator.ino
+++ b/CosmicPiV2Simulator.ino
@@ -8,12 +8,17 @@
 //Strig A out -> 10Hz, sync with trigout
 //Strig B out -> 10Hz, sync with trigout
 //inputs - to check detection is working
-//Flag 0
-//Flag 1
-//Flag 2
+//Flag 0 - digital pin 3
+//Flag 1 - digital pin 4
+//Flag 2 - digital pin 5
 
 //Serial output at 115200
 
+//STM32 flag output detection
+bool flag0 = false;
+bool flag1 = false;
+bool flag2 = false;
+
 
 //variables
 int evt0;
@@ -86,7 +91,13 @@ digitalWrite(TRIG,0);
 digitalWrite(STRIGA,0);
 digitalWrite(STRIGB,0);
 
-  Serial.begin(115200); 
+//attach interrupts
+attachInterrupt(2, Flag0ISR, RISING);
+attachInterrupt(3, Flag1ISR, RISING);
+attachInterrupt(4, Flag2ISR, RISING);
+
+
+Serial.begin(115200); 
 }
 
 void loop() {
@@ -280,7 +291,28 @@ analogWrite(DAC0, psusetpoint);
   
 Serial.print("The loop took ");
 Serial.println(duration);
+if (flag0==true) Serial.println("Saw Flag 0");
+if (flag1==true) Serial.println("Saw Flag 1");
+if (flag2==true) Serial.println("Saw Flag 2");
+flag0=false;
+flag1=false;
+flag2=false;
+
 
 stop_time = micros();
 duration = stop_time - start_time;
-}
\ No newline at end of file
+}
+
+void Flag0ISR()
+{
+  flag0=true;
+}
+
+void Flag1ISR()
+{
+  flag1=true;
+}
+void Flag2ISR()
+{
+  flag2=true;
+}