diff --git a/common/constants.h b/common/constants.h
index d453b9d..f1d044e 100644
--- a/common/constants.h
+++ b/common/constants.h
@@ -20,7 +20,6 @@ const uint8_t COL_PINS[] =
     35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 12, 11, 10, 9, 8, 7, 6
 };
 
-
 const uint8_t ROW_PINS[] =
 {
     5, 4, 3, 2, 1, 0
@@ -31,4 +30,6 @@ const uint16_t CHECKSUM_PERIOD = 65500;
 const uint32_t DEFAULT_BLINK_PERIOD = 500;
 const uint32_t DEFAULT_FADE_TIME = 1000;
 
+static const char* KEYMAP_FILENAME = "Configuration.zkb";
+
 }
diff --git a/core/backlight/backlight.cpp b/core/backlight/backlight.cpp
index edf8318..5cd7f02 100644
--- a/core/backlight/backlight.cpp
+++ b/core/backlight/backlight.cpp
@@ -43,4 +43,13 @@ void Backlight::signal_failure()
     }
 }
 
+void Backlight::signal_success()
+{
+    for (uint8_t i = 0; i < common::constants::TOTAL_NUM_LEDS; ++i)
+    {
+        LEDState& state = led_states[i];
+        state.start_fade(device, colors::GREEN, 10000);
+    }
+}
+
 }
diff --git a/core/backlight/backlight.h b/core/backlight/backlight.h
index c90bbe3..1f4b570 100644
--- a/core/backlight/backlight.h
+++ b/core/backlight/backlight.h
@@ -19,6 +19,7 @@ class Backlight
     void increment_scheme();
 
     void signal_failure();
+    void signal_success();
 
 private:
     Color update_fade(LEDState& state);
diff --git a/core/firmware.cpp b/core/firmware.cpp
index 43efce8..d53460b 100644
--- a/core/firmware.cpp
+++ b/core/firmware.cpp
@@ -15,16 +15,23 @@ Firmware::Firmware(Device& device) :
     wave{device},
 
     backlight{device, schemes, 1}
-{
-    const bool success = keymap.load_from_sd_else_default(device);
-    if (!success)
-    {
-        backlight.signal_failure();
-    }
-}
+{ }
 
 void Firmware::update()
 {
+    if (!loaded_keymap)
+    {
+        const bool success = keymap.load_from_sd_else_default(device);
+        if (success)
+        {
+            backlight.signal_success();
+        }
+        else
+        {
+            backlight.signal_failure();
+        }
+        loaded_keymap = true;
+    }
     device.start_timer();
     keyboard::KeyboardScanResult result;
     key_scanner.scan(result);
@@ -37,6 +44,24 @@ void Firmware::update()
     {
         device.sleep_micros(CYCLE_TIME_MICROS - elapsed);
     }
+
+    // stty 9600 -F /dev/ttyACM0
+    if (device.serial_data_available())
+    {
+        char* buffer;
+        uint32_t num_read_bytes;
+        device.serial_read(buffer, num_read_bytes);
+        const bool success = device.sd_write(common::constants::KEYMAP_FILENAME, buffer, num_read_bytes);
+        delete[] buffer;
+        if (success)
+        {
+            backlight.signal_success();
+        }
+        else
+        {
+            backlight.signal_failure();
+        }
+    }
 }
 
 }
diff --git a/core/firmware.h b/core/firmware.h
index 8977ab6..79c449d 100644
--- a/core/firmware.h
+++ b/core/firmware.h
@@ -25,6 +25,8 @@ class Firmware
     keyboard::KeyQueue key_queue;
     keyboard::KeyMap keymap;
 
+    bool loaded_keymap = false;
+
     // Backlight schemes
     backlight::schemes::Wave wave;
 
diff --git a/core/keyboard/keymap.cpp b/core/keyboard/keymap.cpp
index f449162..400569a 100644
--- a/core/keyboard/keymap.cpp
+++ b/core/keyboard/keymap.cpp
@@ -5,10 +5,6 @@
 namespace core::keyboard
 {
 
-
-const char* KEYMAP_FILENAME = "Configuration.zkb";
-
-
 void KeyReport::add_key(uint16_t key)
 {
     if (util::key_is_valid_standard_key(key))
@@ -296,7 +292,8 @@ bool KeyMap::load_from_sd_else_default(Device& device)
 {
     char* buffer;
     uint32_t num_read_bytes;
-    const bool success = device.sd_read(KEYMAP_FILENAME, buffer, num_read_bytes);
+    const bool success = device.sd_read(common::constants::KEYMAP_FILENAME,
+                                        buffer, num_read_bytes);
     if (success)
     {
         const uint16_t* data = reinterpret_cast<const uint16_t*>(buffer);
diff --git a/core/testutil/testdevice.h b/core/testutil/testdevice.h
index c4b93b0..73a9e10 100644
--- a/core/testutil/testdevice.h
+++ b/core/testutil/testdevice.h
@@ -29,6 +29,9 @@ class TestDeviceBase : public Device
     virtual void set_keyboard_media(const uint16_t) { }
     virtual void keyboard_send() { }
 
+    virtual bool serial_data_available() { return false; }
+    virtual void serial_read(char*&, uint32_t&) { }
+
     virtual bool sd_init() { return false; }
     virtual bool sd_read(const char*, char*&, uint32_t&) const { return false; }
     virtual bool sd_write(const char*, const char*, const uint32_t) { return false; }
diff --git a/device.h b/device.h
index b6d2a22..e130fd9 100644
--- a/device.h
+++ b/device.h
@@ -39,6 +39,21 @@ class Device
     virtual void set_keyboard_media(const uint16_t media) = 0;
     virtual void keyboard_send() = 0;
 
+    /**
+     * Check if there is data available to read from the serial port.
+     * 
+     * @return true if there is data available to read, false otherwise.
+     */
+    virtual bool serial_data_available() = 0;
+
+    /**
+     * Read data from the serial port.
+     * 
+     * @param buffer A pointer to a buffer that will be allocated and filled with the data read from the serial port. Remember to delete[] this buffer when you're done with it.
+     * @param num_read_bytes The number of bytes read from the serial port.
+     */
+    virtual void serial_read(char*& buffer, uint32_t& num_read_bytes) = 0;
+
     /**
      * Initialize the SD card.
      * 
diff --git a/simulator/simulator_device.h b/simulator/simulator_device.h
index e488c62..21fdc7f 100644
--- a/simulator/simulator_device.h
+++ b/simulator/simulator_device.h
@@ -31,6 +31,8 @@ class SimulatorDevice : public Device
     virtual void set_keyboard_media(const uint16_t media) override;
     virtual void keyboard_send() override;
 
+    virtual bool serial_data_available() override { return false; }
+    virtual void serial_read(char*&, uint32_t&) override { }
 
     virtual bool sd_init() override;
     virtual bool sd_read(const char* filename, char*& buffer, uint32_t& num_read_bytes) const override;
diff --git a/teensy_device.cpp b/teensy_device.cpp
index fc01a82..e1262dc 100644
--- a/teensy_device.cpp
+++ b/teensy_device.cpp
@@ -49,71 +49,85 @@ void TeensyDevice::serial_begin(const uint32_t baud)
 void TeensyDevice::serial_print(const char* str)
 {
     Serial.print(str);
+    Serial.flush();
 }
 
 void TeensyDevice::serial_print(uint8_t val)
 {
     Serial.print(val);
+    Serial.flush();
 }
 
 void TeensyDevice::serial_print(uint16_t val)
 {
     Serial.print(val);
+    Serial.flush();
 }
 
 void TeensyDevice::serial_print(uint32_t val)
 {
     Serial.print(val);
+    Serial.flush();
 }
 
 void TeensyDevice::serial_print(int8_t val)
 {
     Serial.print(val);
+    Serial.flush();
 }
 
 void TeensyDevice::serial_print(int16_t val)
 {
     Serial.print(val);
+    Serial.flush();
 }
 
 void TeensyDevice::serial_print(int32_t val)
 {
     Serial.print(val);
+    Serial.flush();
 }
 
 void TeensyDevice::serial_println(const char* str)
 {
     Serial.println(str);
+    Serial.flush();
 }
 
 void TeensyDevice::serial_println(uint8_t val)
 {
     Serial.println(val);
+    Serial.flush();
 }
 
 void TeensyDevice::serial_println(uint16_t val)
 {
     Serial.println(val);
+    Serial.flush();
 }
 
 void TeensyDevice::serial_println(uint32_t val)
 {
     Serial.println(val);
+    Serial.flush();
 }
 
 void TeensyDevice::serial_println(int8_t val)
 {
     Serial.println(val);
+    Serial.flush();
 }
 
 void TeensyDevice::serial_println(int16_t val)
 {
     Serial.println(val);
+    Serial.flush();
 }
 
 void TeensyDevice::serial_println(int32_t val)
 {
     Serial.println(val);
+    Serial.flush();
 }
 
 void TeensyDevice::set_keyboard_key1(const uint8_t code)
@@ -161,6 +175,20 @@ void TeensyDevice::keyboard_send()
     Keyboard.send_now();
 }
 
+bool TeensyDevice::serial_data_available()
+{
+    return Serial.available() > 0;
+}
+
+void TeensyDevice::serial_read(char*& buffer, uint32_t& num_read_bytes)
+{
+    num_read_bytes = Serial.available();
+    serial_print("num_read_bytes: ");
+    serial_println(num_read_bytes);
+    buffer = new char[num_read_bytes];
+    Serial.readBytes(buffer, num_read_bytes);
+}
+
 bool TeensyDevice::sd_init()
 {
     return SD.begin(BUILTIN_SDCARD);
@@ -180,12 +208,20 @@ bool TeensyDevice::sd_read(const char* filename, char*& buffer, uint32_t& num_re
     return false;
 }
 
-bool TeensyDevice::sd_write(const char* filename, const char* buffer, const uint32_t numBytes)
+bool TeensyDevice::sd_write(const char* filename, const char* buffer, const uint32_t num_bytes)
 {
+    if (SD.exists(filename))
+    {
+        const bool removed = SD.remove(filename);
+        if (!removed)
+        {
+            return false;
+        }
+    }
     File file = SD.open(filename, FILE_WRITE);
     if (file)
     {
-        file.write(buffer, numBytes);
+        file.write(buffer, num_bytes);
         file.close();
         return true;
     }
diff --git a/teensy_device.h b/teensy_device.h
index 4809b66..98b44cf 100644
--- a/teensy_device.h
+++ b/teensy_device.h
@@ -27,9 +27,12 @@ class TeensyDevice : public Device
     virtual void set_keyboard_media(const uint16_t media) override;
     virtual void keyboard_send() override;
 
+    virtual bool serial_data_available() override;
+    virtual void serial_read(char*& buffer, uint32_t& num_read_bytes) override;
+
     virtual bool sd_init() override;
-    virtual bool sd_read(const char* filename, char*& buffer, uint32_t& numReadBytes) const override;
-    virtual bool sd_write(const char* filename, const char* buffer, const uint32_t numBytes) override;
+    virtual bool sd_read(const char* filename, char*& buffer, uint32_t& num_read_bytes) const override;
+    virtual bool sd_write(const char* filename, const char* buffer, const uint32_t num_bytes) override;
     virtual uint16_t get_keyboard_leds() override;
 
     virtual void serial_begin(const uint32_t baud) override;
diff --git a/teensy_firmware.cpp b/teensy_firmware.cpp
index 90d91c8..ce4a956 100644
--- a/teensy_firmware.cpp
+++ b/teensy_firmware.cpp
@@ -16,6 +16,7 @@ core::Firmware firmware{device};
 
 void setup()
 {
+    device.sd_init();
     octo.begin();
     pcontroller = new CTeensy4Controller<GRB, WS2811_800kHz>(&octo);
     FastLED.setBrightness(255);
@@ -25,6 +26,7 @@ void setup()
     FastLED.setMaxPowerInVoltsAndMilliamps(5, 900);
     delay(50);
     FastLED.show();
+    device.serial_begin(9600);
 }
 
 void loop()