diff --git a/firmware/CMakeLists.txt b/firmware/CMakeLists.txt
index ce0b6a3..af83803 100644
--- a/firmware/CMakeLists.txt
+++ b/firmware/CMakeLists.txt
@@ -30,4 +30,4 @@ add_custom_target(
     WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
 )
 
-add_executable(Z_DUMMY_TARGET ${SRC_LIST} src/macros.h src/config.h)
+add_executable(Z_DUMMY_TARGET ${SRC_LIST})
diff --git a/firmware/platformio.ini b/firmware/platformio.ini
index 1a3949b..582756b 100644
--- a/firmware/platformio.ini
+++ b/firmware/platformio.ini
@@ -13,16 +13,28 @@
 ;board = wemos_d1_uno32
 ;framework = arduino
 
-[env:s2]
-platform = espressif32
-board = lolin_s2_mini
-framework = arduino
+; ESP32-S2 and C3 both has a problem where the ADC jumps around a LOT
+;[env:s2]
+;platform = espressif32
+;board = lolin_s2_mini
+;framework = arduino
 
 ;[env:c3]
 ;platform = espressif32
 ;board = dfrobot_beetle_esp32c3
 ;framework = arduino
 
+; YD STM32F411CEU6
+[env:stm32f411ce]
+platform = ststm32
+board = blackpill_f411ce
+framework = arduino
+;upload_protocol = stlink
+; Flash using yd-link
+;debug_tool = cmsis-dap
+upload_protocol = cmsis-dap
+
+; Arduino nano is good but too few pins
 ;[env:n328p]
 ;platform = atmelavr
 ;board = nanoatmega328
diff --git a/firmware/src/config.h b/firmware/src/config.h
index 424a98b..4b6365e 100644
--- a/firmware/src/config.h
+++ b/firmware/src/config.h
@@ -1,19 +1,24 @@
 #ifndef FIRMWARE_CONFIG_H
 #define FIRMWARE_CONFIG_H
 
+#include "stm32f4xx_hal.h"
+
 // ========================================
-// Configuration
+// Pin Configuration
 // ========================================
 
+// LED indicator for pulling update
+const int LED_REFRESH = PA13;
+
 // 4 1:16 Multiplexers: GPIO pins for each analog multiplexer that handles 12 sensors of an octave
 // Notes are connected in order: Mux #1 (0-11), Mux #2 (12-23), Mux #3 (24-35), Mux #4 (36-47), Mux #5 (48-59)
 const int NUM_MUX = 5;
 const int PINS_PER_MUX = 12;
-const int MUX_IN[NUM_MUX] = {34, 34, 35, 34, 34};  // Analog signal input
+const int MUX_IN[NUM_MUX] = {PA0, PA1, PA2, PA3, PA4};  // 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_OUT[NUM_MUX_SEL] = {14, 27, 16, 17};
+const int MUX_SEL_OUT[NUM_MUX_SEL] = {PB4, PB5, PB6, PB7};
 
 // 3 1:8 Multiplexers for the midi panel
 const int P_NUM_MUX = 3;
diff --git a/firmware/src/macros.h b/firmware/src/macros.h
index d6c728e..254bfe1 100644
--- a/firmware/src/macros.h
+++ b/firmware/src/macros.h
@@ -5,7 +5,8 @@
 #define u16 uint16_t
 #define u32 uint32_t
 #define u64 uint64_t
-#define timeMillis() std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::system_clock::now().time_since_epoch()).count()
+//#define timeMillis() std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::system_clock::now().time_since_epoch()).count()
+#define timeMillis() HAL_GetTick()
 #define min(a, b) ((a) < (b) ? (a) : (b))
 #define let auto
 #define val const auto
diff --git a/firmware/src/main.cpp b/firmware/src/main.cpp
index c2fbbde..79ca92c 100644
--- a/firmware/src/main.cpp
+++ b/firmware/src/main.cpp
@@ -4,6 +4,8 @@
 #include "macros.h"
 #include "config.h"
 
+#include "stm32f4xx_hal.h"
+
 // ========================================
 // Code
 // ========================================
@@ -26,15 +28,19 @@ const Note notes[] = {
     {"C7", 96}
 };
 
-int lasts[NUM_NOTES];  // variable to store the value coming from the sensor
+u32 lasts[NUM_NOTES];  // variable to store the value coming from the sensor
 u64 last_hit_times[NUM_NOTES];
 
 val max_sensor = 4096;
 val max_threshold = 2000;
 val active_threshold = 100;  // Minimum value to be considered as a hit
 
+let led_refresh_on = false;
+
 void setup()
 {
+    HAL_Init();
+
     // Initialize pin and serial
     for (int pin: MUX_IN) pinMode(pin, INPUT);
     for (int pin: MUX_SEL_OUT) pinMode(pin, OUTPUT);
@@ -49,7 +55,7 @@ void setup()
  *
  * @param id Sensor index
  */
-void on_sensor_update(int id, u64 time, int last, int current)
+void on_sensor_update(int id, u64 time, u32 last, u32 current)
 {
     // If the last value is larger than the current value, check timeout
     if (last > current && last > active_threshold)
@@ -77,6 +83,8 @@ void loop()
     u64 time = timeMillis();
     u64 elapsed = time - start_time;
 
+    // Toggle LED refresh indicator
+    digitalWrite(LED_REFRESH, led_refresh_on = !led_refresh_on);
 //    Serial.printf("%" PRIu64 "=============\r\n", elapsed);
 
     // Loop through each multiplexer state
@@ -96,11 +104,11 @@ void loop()
             if (note_id >= NUM_NOTES) break;
 
             // Read the analog input
-            int v = analogRead(MUX_IN[j]);
+            u32 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("%s %d\r\n", notes[note_id].name, v);
+                Serial.printf("%s %d\r\n", notes[note_id].name, v);
                 on_sensor_update(note_id, time, lasts[note_id], v);
             }
             lasts[note_id] = v;