diff --git a/firmware/src/main.cpp b/firmware/src/main.cpp
index 7bd9288..116f515 100644
--- a/firmware/src/main.cpp
+++ b/firmware/src/main.cpp
@@ -19,7 +19,6 @@ typedef struct note {
 
 // 61 Notes from C2 to C7
 const int NUM_NOTES = 61;
-
 const Note notes[] = {
     {"C2", 36}, {"C#2", 37}, {"D2", 38}, {"D#2", 39}, {"E2", 40}, {"F2", 41}, {"F#2", 42}, {"G2", 43}, {"G#2", 44}, {"A2", 45}, {"A#2", 46}, {"B2", 47},
     {"C3", 48}, {"C#3", 49}, {"D3", 50}, {"D#3", 51}, {"E3", 52}, {"F3", 53}, {"F#3", 54}, {"G3", 55}, {"G#3", 56}, {"A3", 57}, {"A#3", 58}, {"B3", 59},
@@ -30,8 +29,13 @@ const Note notes[] = {
 };
 
 // 4 Multiplexers: GPIO pins for each analog multiplexer that handles 16 sensors
+// Notes are connected in order: Mux #1 (0-15), Mux #2 (16-31), Mux #3 (32-47), Mux #4 (48-61)
 const int NUM_MUX = 4;
-const int mux[] = {35, 34, 36, 39};
+const int PINS_PER_MUX = 16;
+const int mux_in[] = {35, 34, 36, 39};  // Analog signal input
+// Select pins for every multiplexer, each multiplexer has 4 select pins, all sel0 are connected to 14, etc.
+const int NUM_MUX_SEL = 4;
+const int mux_sel[4] = {14, 27, 16, 17};
 
 int lasts[NUM_NOTES];  // variable to store the value coming from the sensor
 u64 last_hit_times[NUM_NOTES];
@@ -43,10 +47,15 @@ int active_threshold = 400;  // Minimum value to be considered as a hit
 void setup()
 {
     // Initialize pin and serial
-    for (int pin : pins) pinMode(pin, INPUT);
+    for (int pin: mux_in) pinMode(pin, INPUT);
+    for (int pin: mux_sel) pinMode(pin, OUTPUT);
     Serial.begin(9600);
     Serial.printf("Initialized\r\n");
 
+    // Testing pin
+    pinMode(2, OUTPUT);
+    analogWrite(2, 255);
+
     start_time = timeMillis();
 }
 
@@ -58,9 +67,11 @@ void setup()
 void on_sensor_update(int id, u64 time, int last, int current)
 {
     // If the last value is larger than the current value, check timeout
-    if (last > current && last > active_threshold) {
+    if (last > current && last > active_threshold)
+    {
         u64 elapsed = time - last_hit_times[id];
-        if (elapsed < 150) {
+        if (elapsed < 150)
+        {
             // If the last hit is too close, ignore this hit
             return;
         }
@@ -68,25 +79,47 @@ void on_sensor_update(int id, u64 time, int last, int current)
         // The last value is a local maximum,
         // and we read it as the hit strength of our note. Send midi command to the host.
         // /hit <note> <velocity>
-        Serial.printf("/hit %d %d\r\n", notes[id], min((last - active_threshold) * 127 / (max_threshold - active_threshold), 127));
+        Serial.printf("/hit %d %d\r\n", notes[id].midi,
+                      min((last - active_threshold) * 127 / (max_threshold - active_threshold), 127));
 
         // Update last hit time
         last_hit_times[id] = time;
     }
 }
 
-void loop() {
+void loop()
+{
     u64 time = timeMillis();
+    u64 elapsed = time - start_time;
 
-    // Read sensor value from each pin
-    for (int i = 0; i < NUM_SENSORS; i++) {
-        int v = analogRead(pins[i]);
-        if (v != lasts[i]) {
-            u64 elapsed = time - start_time;
-            Serial.printf("Sensor #%d - %" PRIu64 ": %d\r\n", i, elapsed, v);
+    Serial.printf("%" PRIu64 "=============\r\n", elapsed);
 
-            on_sensor_update(i, time, lasts[i], v);
+    // Loop through each multiplexer state
+    for (int i = 0; i < PINS_PER_MUX; i++)
+    {
+        // Set select pins
+        for (int j = 0; j < NUM_MUX_SEL; j++)
+        {
+            // i >> j is the jth bit of i
+            digitalWrite(mux_sel[j], (i >> j) & 1);
+        }
+
+        // Read four input pins from the multiplexer
+        for (int j = 0; j < NUM_MUX; j++)
+        {
+            int note_id = j * PINS_PER_MUX + i;
+            if (note_id >= NUM_NOTES) break;
+
+            // Read the analog input
+            int v = analogRead(mux_in[j]);
+            if (v != lasts[note_id])
+            {
+                // Serial prints are really slow, so don't use them in debug mode
+                // Serial.printf("#%d %d\r\n", note_id, v);
+                on_sensor_update(note_id, time, lasts[note_id], v);
+            }
+            lasts[note_id] = v;
         }
-        lasts[i] = v;
     }
+//    Serial.printf("Loop %" PRIu64 "\r\n", elapsed);
 }
\ No newline at end of file