diff --git a/tach/tach.ino b/tach/tach.ino
index 3ffbfa1..5057d31 100644
--- a/tach/tach.ino
+++ b/tach/tach.ino
@@ -7,6 +7,14 @@
 
 Adafruit_7segment matrix = Adafruit_7segment();
 
+// --- Tachometer variables ---
+const int TACH_INTERRUPT_PIN = A0; // Or any other digital pin capable of interrupts
+volatile unsigned long pulse_count = 0;
+
+// --- Interrupt Service Routine (ISR) ---
+void count_pulse() {
+  pulse_count++;
+}
 
 void show(int num) {
 	matrix.print(num, DEC);
@@ -19,6 +27,10 @@ void setup() {
 	Serial.begin(115200);
 	// Serial.setDebugOutput(true);
 
+  // --- Setup Tachometer Interrupt ---
+  pinMode(TACH_INTERRUPT_PIN, INPUT_PULLUP); // Set pin as input with internal pull-up resistor
+  attachInterrupt(digitalPinToInterrupt(TACH_INTERRUPT_PIN), count_pulse, RISING);
+
 	delay(1000);
 
 	Serial.println();