diff --git a/.cproject b/.cproject
index 827a8d3..d553e3f 100644
--- a/.cproject
+++ b/.cproject
@@ -27,7 +27,7 @@
                             </option>
                             <option id="com.ti.ccstudio.buildDefinitions.core.OPT_CODEGEN_VERSION.1502413104" superClass="com.ti.ccstudio.buildDefinitions.core.OPT_CODEGEN_VERSION" value="21.6.1.LTS" valueType="string"/>
                             <targetPlatform id="com.ti.ccstudio.buildDefinitions.MSP430_21.6.exe.targetPlatformDebug.1741833122" name="Platform" superClass="com.ti.ccstudio.buildDefinitions.MSP430_21.6.exe.targetPlatformDebug"/>
-                            <builder buildPath="${BuildDirectory}" id="com.ti.ccstudio.buildDefinitions.MSP430_21.6.exe.builderDebug.235413854" name="GNU Make.Debug" parallelBuildOn="true" parallelizationNumber="optimal" superClass="com.ti.ccstudio.buildDefinitions.MSP430_21.6.exe.builderDebug"/>
+                            <builder buildPath="${BuildDirectory}" id="com.ti.ccstudio.buildDefinitions.MSP430_21.6.exe.builderDebug.235413854" keepEnvironmentInBuildfile="false" name="GNU Make" parallelBuildOn="true" parallelizationNumber="optimal" superClass="com.ti.ccstudio.buildDefinitions.MSP430_21.6.exe.builderDebug"/>
                             <tool id="com.ti.ccstudio.buildDefinitions.MSP430_21.6.exe.compilerDebug.281898955" name="MSP430 Compiler" superClass="com.ti.ccstudio.buildDefinitions.MSP430_21.6.exe.compilerDebug">
                                 <option id="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.DEFINE.925722857" superClass="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.DEFINE" valueType="definedSymbols">
                                     <listOptionValue value="__MSP430FR2355__"/>
@@ -40,7 +40,7 @@
                                 <option id="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.SILICON_ERRATA.CPU22.253852873" superClass="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.SILICON_ERRATA.CPU22" value="true" valueType="boolean"/>
                                 <option id="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.SILICON_ERRATA.CPU40.916653631" superClass="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.SILICON_ERRATA.CPU40" value="true" valueType="boolean"/>
                                 <option id="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.SILICON_VERSION.973894696" superClass="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.SILICON_VERSION" value="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.SILICON_VERSION.mspx" valueType="enumerated"/>
-                                <option id="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.PRINTF_SUPPORT.1310228180" superClass="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.PRINTF_SUPPORT" value="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.PRINTF_SUPPORT.minimal" valueType="enumerated"/>
+                                <option id="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.PRINTF_SUPPORT.1310228180" superClass="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.PRINTF_SUPPORT" value="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.PRINTF_SUPPORT.full" valueType="enumerated"/>
                                 <option id="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.DEBUGGING_MODEL.1031813406" superClass="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.DEBUGGING_MODEL" value="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.DEBUGGING_MODEL.SYMDEBUG__DWARF" valueType="enumerated"/>
                                 <option id="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.DISPLAY_ERROR_NUMBER.482096263" superClass="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.DISPLAY_ERROR_NUMBER" value="true" valueType="boolean"/>
                                 <option id="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.DIAG_WARNING.1891170450" superClass="com.ti.ccstudio.buildDefinitions.MSP430_21.6.compilerID.DIAG_WARNING" valueType="stringList">
diff --git a/Debug/.clangd/compile_commands.json b/Debug/.clangd/compile_commands.json
index 89230d1..b23d093 100644
--- a/Debug/.clangd/compile_commands.json
+++ b/Debug/.clangd/compile_commands.json
@@ -148,5 +148,15 @@
       "directory" : "/home/frederik/workspace_ccstheia/ESR-11/Debug",
       "command"   : "clang++ -I\"/home/frederik/.ti/ccs2010/ccs/ccs_base/msp430/include\" -I\"/home/frederik/workspace_ccstheia/ESR-11\" -I\"/home/frederik/workspace_ccstheia/ESR-11/jsmn\" -I\"/home/frederik/workspace_ccstheia/ESR-11/driverlib/MSP430FR2xx_4xx\" -I\"/home/frederik/.ti/ccs2010/ccs/tools/compiler/ti-cgt-msp430_21.6.1.LTS/include\" -D__MSP430FR2355__ -D_FRWP_ENABLE -D_INFO_FRWP_ENABLE -xc",
       "file"      : "/home/frederik/workspace_ccstheia/ESR-11/src/state_machine.c"
+   },
+   {
+      "directory" : "/home/frederik/workspace_ccstheia/ESR-11/Debug",
+      "command"   : "clang++ -I\"/home/frederik/.ti/ccs2010/ccs/ccs_base/msp430/include\" -I\"/home/frederik/workspace_ccstheia/ESR-11\" -I\"/home/frederik/workspace_ccstheia/ESR-11/jsmn\" -I\"/home/frederik/workspace_ccstheia/ESR-11/driverlib/MSP430FR2xx_4xx\" -I\"/home/frederik/.ti/ccs2010/ccs/tools/compiler/ti-cgt-msp430_21.6.1.LTS/include\" -D__MSP430FR2355__ -D_FRWP_ENABLE -D_INFO_FRWP_ENABLE -xc",
+      "file"      : "/home/frederik/workspace_ccstheia/ESR-11/src/timer.c"
+   },
+   {
+      "directory" : "/home/frederik/workspace_ccstheia/ESR-11/Debug",
+      "command"   : "clang++ -I\"/home/frederik/.ti/ccs2010/ccs/ccs_base/msp430/include\" -I\"/home/frederik/workspace_ccstheia/ESR-11\" -I\"/home/frederik/workspace_ccstheia/ESR-11/jsmn\" -I\"/home/frederik/workspace_ccstheia/ESR-11/driverlib/MSP430FR2xx_4xx\" -I\"/home/frederik/.ti/ccs2010/ccs/tools/compiler/ti-cgt-msp430_21.6.1.LTS/include\" -D__MSP430FR2355__ -D_FRWP_ENABLE -D_INFO_FRWP_ENABLE -xc",
+      "file"      : "/home/frederik/workspace_ccstheia/ESR-11/src/door_sensor.c"
    }
 ]
diff --git a/main.c b/main.c
index 8015b46..4cffd0c 100755
--- a/main.c
+++ b/main.c
@@ -18,72 +18,13 @@
 #include "src/i2c.h"
 #include "src/lcd.h"
 #include "src/Board.h"
+#include "src/timer.h"
+#include "src/state_machine.h"
 
 /** On-board LED port and pin (used by Morse module) */
 #define LED_PORT        GPIO_PORT_P1    /**< On-board LED port */
 #define LED_PIN         GPIO_PIN0       /**< On-board LED pin */
 
-volatile char last_key_pressed = '\0';
-volatile bool key_changed = false;
-
-/**
- * @brief Keypad callback invoked on key press interrupt.
- * @param key  ASCII character of pressed key
- *
- * Stores key, sets ready flag, and blinks Morse code on LED.
- */
-static void myKeyHandler(char key)
-{
-    last_key_pressed = key;
-    key_changed = true;
-}
-
-void init_timer(void) {
-    static Timer_B_initUpModeParam param = {0};
-
-    param.clockSource = TIMER_B_CLOCKSOURCE_SMCLK;
-    param.clockSourceDivider = TIMER_B_CLOCKSOURCE_DIVIDER_1;
-    param.timerPeriod = 999;        // wenn 1000 Taktimpulse gezählt
-                                    // wurden, erfolgt ein Interrupt
-                                    // Periodendauer somit 1ms
-    param.timerInterruptEnable_TBIE =
-            TIMER_B_TBIE_INTERRUPT_DISABLE;         // no interrupt on 0x0000
-    param.captureCompareInterruptEnable_CCR0_CCIE =
-        TIMER_B_CAPTURECOMPARE_INTERRUPT_ENABLE;    // interrupt on TRmax
-    param.timerClear = TIMER_B_DO_CLEAR;
-    param.startTimer = true;
-
-    // start Timer:
-    Timer_B_initUpMode(TB0_BASE, &param);
-}
-
-void init_i2c(void) {
-    EUSCI_B_I2C_initMasterParam param = {0};
-
-    // Configure Pins for I2C
-    /*
-    * Select Port 1
-    * Set Pin 2, 3 to input with function, (UCB0SIMO/UCB0SDA, UCB0SOMI/UCB0SCL).
-    */
-
-    GPIO_setAsPeripheralModuleFunctionInputPin(GPIO_PORT_UCB0SCL, GPIO_PIN_UCB0SCL, GPIO_FUNCTION_UCB0SCL);
-    GPIO_setAsPeripheralModuleFunctionInputPin(GPIO_PORT_UCB0SDA, GPIO_PIN_UCB0SDA, GPIO_FUNCTION_UCB0SDA);
-
-    param.selectClockSource = EUSCI_B_I2C_CLOCKSOURCE_SMCLK;
-    param.i2cClk = CS_getSMCLK();
-    param.dataRate = EUSCI_B_I2C_SET_DATA_RATE_100KBPS;
-    param.byteCounterThreshold = 1;
-    param.autoSTOPGeneration = EUSCI_B_I2C_NO_AUTO_STOP;
-    EUSCI_B_I2C_initMaster(EUSCI_B0_BASE, &param);
-
-    //Specify slave address
-    EUSCI_B_I2C_setSlaveAddress(EUSCI_B0_BASE, 0x27);
-    //Set in transmit mode
-    EUSCI_B_I2C_setMode(EUSCI_B0_BASE, EUSCI_B_I2C_TRANSMIT_MODE);
-    //Enable I2C Module to start operations
-    EUSCI_B_I2C_enable(EUSCI_B0_BASE);
-}
-
 /**
  * @brief Main application entry point.
  *
@@ -102,48 +43,10 @@ int main(void)
     GPIO_setAsOutputPin(LED_PORT, LED_PIN);
     GPIO_setOutputLowOnPin(LED_PORT, LED_PIN);
 
-    /* Initialize keypad interrupt driver */
-    initKeypadInterrupts(myKeyHandler);
-
     init_timer();
+    i2c_init();
+    lcd_init();
 
-    I2C_init();                  /* I²C-Master initialisieren */
-    lcd_init();                  /* LCD initialisieren */
-
-    lcd_set_cursor(0, 0);
-    lcd_print("Press any Key!");
-
-    /* Enter low-power mode and wait for key interrupts */
-    for (;;) {
-        __bis_SR_register(LPM0_bits | GIE);  /* Enter LPM0 with interrupts enabled */
-        __no_operation();
-
-        if (key_changed) {
-            lcd_set_cursor(1, 0);
-            char output[20] = "Key pressed:  ";
-            output[13] = last_key_pressed;
-
-            lcd_print(output);
-
-            key_changed = false;
-        }
-    }
-}
-
-/**
- * @brief Führt eine blockierende Wartezeit aus.
- * @param ms Zeit in Millisekunden
- */
-void sleep(uint16_t ms) {
-    while (ms--) {
-        __bis_SR_register(LPM0_bits + GIE);
-        __no_operation();
-    }
-}
-
-// TimerB0 Interrupt Vector (TBxIV) handler
-#pragma vector=TIMER0_B0_VECTOR
-__interrupt void TIMER0_B0_ISR(void)
-{
-    __bic_SR_register_on_exit(LPM0_bits);
-}
+    sm_init();
+    sm_loop();
+}
\ No newline at end of file
diff --git a/src/door_sensor.c b/src/door_sensor.c
new file mode 100644
index 0000000..65878cb
--- /dev/null
+++ b/src/door_sensor.c
@@ -0,0 +1,55 @@
+#include <stdint.h>
+#include <msp430.h>
+#include <driverlib.h>
+#include <stdbool.h>
+#include "door_sensor.h"
+#include "constants.h"
+
+#define SENSOR_PORT   GPIO_PORT_P2
+#define SENSOR_PIN    GPIO_PIN0
+#define SENSOR_VECTOR PORT2_VECTOR
+
+/** User callback invoked on confirmed key press */
+static DoorOpenedCallback_t doorOpenedCallback = NULL;
+static DoorClosedCallback_t doorClosedCallback = NULL;
+
+void door_init(DoorOpenedCallback_t ocb, DoorClosedCallback_t ccb) {
+    doorOpenedCallback = ocb;
+    doorClosedCallback = ccb;
+
+    /* Configure port as pull up with interrupt */
+    GPIO_setAsInputPinWithPullUpResistor(GPIO_PORT_P2, GPIO_PIN0);
+    GPIO_clearInterrupt(GPIO_PORT_P2, GPIO_PIN0);
+    GPIO_selectInterruptEdge(GPIO_PORT_P2, GPIO_PIN0, GPIO_LOW_TO_HIGH_TRANSITION);
+    GPIO_enableInterrupt(GPIO_PORT_P2, GPIO_PIN0);
+
+    /* Enable global interrupts */
+    __enable_interrupt();
+}
+
+volatile bool door_last_open = false;
+
+/**
+ * @brief  Interrupt Service Routine for PORT2
+ */
+#pragma vector=SENSOR_VECTOR
+__interrupt void SENSOR_ISR(void)
+{
+    uint16_t status = GPIO_getInterruptStatus(SENSOR_PORT, SENSOR_PIN);
+
+    if (status) {
+        if (door_last_open) {
+            if (doorClosedCallback)
+                doorClosedCallback();
+            GPIO_selectInterruptEdge(GPIO_PORT_P2, GPIO_PIN0, GPIO_LOW_TO_HIGH_TRANSITION);
+        } else {
+            if (doorOpenedCallback)
+                doorOpenedCallback();
+            GPIO_selectInterruptEdge(GPIO_PORT_P2, GPIO_PIN0, GPIO_HIGH_TO_LOW_TRANSITION);
+        }
+    }
+
+    GPIO_clearInterrupt(SENSOR_PORT, SENSOR_PIN);
+
+    door_last_open = !door_last_open;
+}
diff --git a/src/door_sensor.h b/src/door_sensor.h
new file mode 100644
index 0000000..5b43318
--- /dev/null
+++ b/src/door_sensor.h
@@ -0,0 +1,13 @@
+#ifndef DOOR_H
+#define DOOR_H
+
+/**
+ * @brief Callback invoked on a confirmed key press.
+ * @param key ASCII character of the pressed key.
+ */
+typedef void (*DoorOpenedCallback_t)(void);
+typedef void (*DoorClosedCallback_t)(void);
+
+void door_init(DoorOpenedCallback_t ocb, DoorClosedCallback_t ccb);
+
+#endif // DOOR_H
\ No newline at end of file
diff --git a/src/i2c.c b/src/i2c.c
index 1e249ae..2bfcc89 100644
--- a/src/i2c.c
+++ b/src/i2c.c
@@ -28,7 +28,7 @@ static char dataIn;
 
 static volatile bool i2cDone = false;
 
-void I2C_init(void)
+void i2c_init(void)
 {
     // USCI in Reset setzen um Konfiguration zu ermöglichen
     UCB0CTLW0 |= UCSWRST;
@@ -56,7 +56,7 @@ void I2C_init(void)
     __enable_interrupt();
 }
 
-void I2C_write(uint8_t slaveAddress, char data[], uint8_t length)
+void i2c_write(uint8_t slaveAddress, char data[], uint8_t length)
 {
     UCB0I2CSA = slaveAddress;
     packet = data;
@@ -77,11 +77,11 @@ void I2C_write(uint8_t slaveAddress, char data[], uint8_t length)
     }
 }
 
-char I2C_read_reg(uint8_t slaveAddress, uint8_t registerAddress)
+char i2c_read_reg(uint8_t slaveAddress, uint8_t registerAddress)
 {
     // Registeradresse zuerst senden
     char addressBuffer[1] = {registerAddress};
-    I2C_write(slaveAddress, addressBuffer, 1);
+    i2c_write(slaveAddress, addressBuffer, 1);
 
     // In Empfangsmodus wechseln und 1 Byte anfordern
     UCB0CTLW0 &= ~UCTR;
diff --git a/src/i2c.h b/src/i2c.h
index 16ec6e5..f74dfc6 100644
--- a/src/i2c.h
+++ b/src/i2c.h
@@ -21,7 +21,7 @@
 /**
  * @brief Initialize the I2C module as master (SMCLK/20 → 50 kHz SCL).
  */
-void I2C_init(void);
+void i2c_init(void);
 
 /**
  * @brief Send a data packet to an I2C slave.
@@ -29,7 +29,7 @@ void I2C_init(void);
  * @param data Pointer to the data buffer to send.
  * @param length Number of bytes to send.
  */
-void I2C_write(uint8_t slaveAddress, char data[], uint8_t length);
+void i2c_write(uint8_t slaveAddress, char data[], uint8_t length);
 
 /**
  * @brief Read a single byte from a specific register of an I2C slave.
@@ -37,6 +37,6 @@ void I2C_write(uint8_t slaveAddress, char data[], uint8_t length);
  * @param registerAddress Register address to read.
  * @return The byte read from the device.
  */
-char I2C_read_reg(uint8_t slaveAddress, uint8_t registerAddress);
+char i2c_read_reg(uint8_t slaveAddress, uint8_t registerAddress);
 
 #endif /* I2C_H */
diff --git a/src/keypad.c b/src/keypad.c
index 856b3ad..0570bbc 100644
--- a/src/keypad.c
+++ b/src/keypad.c
@@ -54,7 +54,7 @@ static KeypadCallback_t keyCallback = NULL;
  * @param  colIdx  Index of column (0–3) that triggered interrupt
  * @return ASCII character of pressed key, or 0 if none detected
  */
-static char scanRowForColumn(uint8_t colIdx)
+static char scan_row_for_column(uint8_t colIdx)
 {
     char result = 0;
     unsigned int r;
@@ -85,7 +85,7 @@ static char scanRowForColumn(uint8_t colIdx)
  *         wait for release, then re-arm interrupts.
  * @param  colIdx  Index of column that triggered the interrupt
  */
-static void handleColumnInterrupt(uint8_t colIdx)
+static void handle_column_interrupt(uint8_t colIdx)
 {
     unsigned int i;
 
@@ -99,7 +99,7 @@ static void handleColumnInterrupt(uint8_t colIdx)
 
     /* Identify pressed key and invoke callback if set */
     {
-        char key = scanRowForColumn(colIdx);
+        char key = scan_row_for_column(colIdx);
         if (key && keyCallback) {
             keyCallback(key);
         }
@@ -137,12 +137,12 @@ __interrupt void PORT1_ISR(void)
     uint16_t status = GPIO_getInterruptStatus(GPIO_PORT_P1, mask);
 
     if (status & colPin[COL1]) {
-        handleColumnInterrupt(COL1);
+        handle_column_interrupt(COL1);
         __bic_SR_register_on_exit(LPM0_bits);
     }
  
     if (status & colPin[COL3]) {
-        handleColumnInterrupt(COL3);
+        handle_column_interrupt(COL3);
         __bic_SR_register_on_exit(LPM0_bits);
     }
 
@@ -159,12 +159,12 @@ __interrupt void PORT3_ISR(void)
     uint16_t status = GPIO_getInterruptStatus(GPIO_PORT_P3, mask);
 
     if (status & colPin[COL0]) {
-        handleColumnInterrupt(COL0);
+        handle_column_interrupt(COL0);
         __bic_SR_register_on_exit(LPM0_bits);
     }
     
     if (status & colPin[COL2]) {
-        handleColumnInterrupt(COL2);
+        handle_column_interrupt(COL2);
         __bic_SR_register_on_exit(LPM0_bits);
     }
 
@@ -179,7 +179,7 @@ __interrupt void PORT3_ISR(void)
  * @brief  Initialize keypad GPIOs and interrupts.
  * @param  cb  Callback invoked with ASCII key on press
  */
-void initKeypadInterrupts(KeypadCallback_t cb)
+void keypad_init(KeypadCallback_t cb)
 {
     unsigned int i;
     keyCallback = cb;
diff --git a/src/keypad.h b/src/keypad.h
index 8b19e2d..d391715 100644
--- a/src/keypad.h
+++ b/src/keypad.h
@@ -27,6 +27,6 @@ typedef void (*KeypadCallback_t)(char key);
  * @brief Initialize the keypad pins and interrupts.
  * @param cb User callback for key events.
  */
-void initKeypadInterrupts(KeypadCallback_t cb);
+void keypad_init(KeypadCallback_t cb);
 
 #endif /* KEYPAD_H */
diff --git a/src/lcd.c b/src/lcd.c
index 87897c8..8b73843 100644
--- a/src/lcd.c
+++ b/src/lcd.c
@@ -11,13 +11,13 @@ static void lcd_write_nibble(uint8_t nibble, uint8_t control)
     /* High-Nibble in die oberen 4 Bits */
     buf[0] = (nibble << 4) | control | LCD_BACKLIGHT;
     /* EN=1 */
-    I2C_write(LCD_I2C_ADDR, buf, 1);
+    i2c_write(LCD_I2C_ADDR, buf, 1);
     buf[0] |= LCD_ENABLE;
-    I2C_write(LCD_I2C_ADDR, buf, 1);
+    i2c_write(LCD_I2C_ADDR, buf, 1);
     __delay_cycles(500);        /* ca. 50 µs @ 1 MHz */
     /* EN=0 */
     buf[0] &= ~LCD_ENABLE;
-    I2C_write(LCD_I2C_ADDR, buf, 1);
+    i2c_write(LCD_I2C_ADDR, buf, 1);
     __delay_cycles(500);
 }
 
diff --git a/src/morse.c b/src/morse.c
index bf04f14..ec0fda6 100644
--- a/src/morse.c
+++ b/src/morse.c
@@ -32,7 +32,7 @@
 /**
  * @brief Blink the LED for a dot: on 1 unit, off 1 unit.
  */
-static void blinkDot(void)
+static void blink_dot(void)
 {
     GPIO_setOutputHighOnPin(LED_PORT, LED_PIN);
     __delay_cycles(MORSE_UNIT_CYCLES);
@@ -43,7 +43,7 @@ static void blinkDot(void)
 /**
  * @brief Blink the LED for a dash: on 3 units, off 1 unit.
  */
-static void blinkDash(void)
+static void blink_dash(void)
 {
     GPIO_setOutputHighOnPin(LED_PORT, LED_PIN);
     __delay_cycles(3 * MORSE_UNIT_CYCLES);
@@ -102,7 +102,7 @@ static const char *lookupMorse(char in)
  * Unlocks FRAM I/O power-on default high-impedance lock,
  * then configures LED pin as output low.
  */
-void morseInit(void)
+void morse_init(void)
 {
     PMM_unlockLPM5();
     GPIO_setAsOutputPin(LED_PORT, LED_PIN);
@@ -118,7 +118,7 @@ void morseInit(void)
  *
  * @param c  Character to blink (A–Z, a–z, 0–9)
  */
-void blinkMorseChar(char c)
+void blink_morse_char(char c)
 {
     const char *pattern = lookupMorse(c);
     const char *p;
@@ -130,9 +130,9 @@ void blinkMorseChar(char c)
     /* Blink each element in pattern */
     for (p = pattern; *p; p++) {
         if (*p == '.') {
-            blinkDot();
+            blink_dot();
         } else if (*p == '-') {
-            blinkDash();
+            blink_dash();
         }
     }
 
diff --git a/src/morse.h b/src/morse.h
index 882b770..bb776c1 100644
--- a/src/morse.h
+++ b/src/morse.h
@@ -10,7 +10,7 @@
 /**
  * @brief Initialize LED output pin (P1.0) for Morse blinking.
  */
-void morseInit(void);
+void morse_init(void);
 
 /**
  * @brief Blink an alphanumeric character in Morse code.
@@ -18,6 +18,6 @@ void morseInit(void);
  * Supports A–Z (case-insensitive) and 0–9. Others are ignored.
  * @param c  Character to blink
  */
-void blinkMorseChar(char c);
+void blink_morse_char(char c);
 
 #endif // MORSE_H
diff --git a/src/state_machine.c b/src/state_machine.c
index df8d82b..e80a490 100644
--- a/src/state_machine.c
+++ b/src/state_machine.c
@@ -12,4 +12,365 @@
  * @date 2025-07-02
  */
 
- 
\ No newline at end of file
+#include <stdbool.h>
+#include <msp430.h>
+#include <driverlib.h>
+#include <stdio.h>
+#include <ctype.h>
+#include "keypad.h"
+#include "lcd.h"
+#include "morse.h"
+#include "door_sensor.h"
+#include "state_machine.h"
+#include "timer.h"
+
+volatile char keypad_last_key = '\0';
+volatile bool keypad_flag_chg = false;
+
+volatile bool allow_open = false;
+
+/* Function Declarations */
+void handle_interrupt(void);
+void buzz_invalid_input(void);
+void sound_alarm(void);
+void reset_alarm(void);
+void transition(State_t state);
+void ui_draw_idle(void);
+void ui_draw_sel_count(void);
+void ui_draw_confirmed(void);
+void ui_draw_error(void);
+void ui_draw_open(void);
+void ui_draw_none_selected(void);
+void ui_draw_reset(void);
+void reset_amount();
+void reset_amounts();
+bool any_selected(void);
+
+volatile State_t current_state = STATE_IDLE;
+volatile bool state_chg = false;
+
+volatile uint8_t count_a = 0;
+volatile uint8_t count_b = 0;
+volatile uint8_t count_c = 0;
+volatile uint8_t count_d = 0;
+volatile SelectedBev_t selected_bev = BEV_A;
+
+volatile bool door_open = false;
+
+void handle_input_idle(unsigned char key) {
+    switch (key) {
+        case 'A':
+            selected_bev = BEV_A;
+            transition(STATE_SEL_COUNT);
+            break;
+        case 'B':
+            selected_bev = BEV_B;
+            transition(STATE_SEL_COUNT);
+            break;
+        case 'C':
+            selected_bev = BEV_C;
+            transition(STATE_SEL_COUNT);
+            break;
+        case 'D':
+            selected_bev = BEV_D;
+            transition(STATE_SEL_COUNT);
+            break;
+        default:
+            buzz_invalid_input();
+    }
+}
+
+void handle_input_confirmed(unsigned char key) {
+    switch (key) {
+        case 'A':
+            selected_bev = BEV_A;
+            transition(STATE_SEL_COUNT);
+            break;
+        case 'B':
+            selected_bev = BEV_B;
+            transition(STATE_SEL_COUNT);
+            break;
+        case 'C':
+            selected_bev = BEV_C;
+            transition(STATE_SEL_COUNT);
+            break;
+        case 'D':
+            selected_bev = BEV_D;
+            transition(STATE_SEL_COUNT);
+            break;
+        case '*':
+            reset_amounts();
+            transition(STATE_RESET);
+            break;
+        default:
+            buzz_invalid_input();
+    }
+}
+
+void update_amount(uint8_t new_digit) {
+    switch (selected_bev) {
+        case BEV_A:
+            if (count_a * 10 + new_digit < 255)
+                count_a = count_a * 10 + new_digit;
+            break;
+        case BEV_B:
+            if (count_b * 10 + new_digit < 255)
+                count_b = count_b * 10 + new_digit;
+            break;
+        case BEV_C:
+            if (count_c * 10 + new_digit < 255)
+                count_c = count_c * 10 + new_digit;
+            break;
+        case BEV_D:
+            if (count_d * 10 + new_digit < 255)
+                count_d = count_d * 10 + new_digit;
+            break;
+    }
+}
+
+void reset_amount() {
+    switch (selected_bev) {
+        case BEV_A:
+            count_a = 0;
+            break;
+        case BEV_B:
+            count_b = 0;
+            break;
+        case BEV_C:
+            count_c = 0;
+            break;
+        case BEV_D:
+            count_d = 0;
+            break;
+    }
+}
+
+void reset_amounts() {
+    count_a = 0;
+    count_b = 0;
+    count_c = 0;
+    count_d = 0;
+}
+
+void handle_input_sel_count(unsigned char key) {
+    // Check if input is number
+    if (key >= '0' && key <= '9') {
+        update_amount((uint8_t) key - '0');
+        transition(current_state);
+    } else if (key == '#') {
+        if (door_open) {
+            transition(STATE_OPEN);
+        } else {
+            if (!any_selected()) {
+                transition(STATE_NONE_SELECTED);
+            } else {
+                transition(STATE_CONFIRMED);
+            }
+        }
+    } else if (key == '*') {
+        reset_amount();
+        transition(current_state);
+    } else {
+        handle_input_idle(key);
+    }
+}
+
+/**
+ * @brief Keypad callback invoked on key press interrupt.
+ * @param key  ASCII character of pressed key
+ *
+ * Stores key, sets ready flag, and blinks Morse code on LED.
+ */
+static void keypad_handler(char key)
+{
+    keypad_last_key = key;
+    keypad_flag_chg = true;
+
+    switch (current_state) {
+        case STATE_IDLE:
+            handle_input_idle(key);
+            break;
+        case STATE_SEL_COUNT:
+            handle_input_sel_count(key);
+            break;
+        case STATE_CONFIRMED:
+            handle_input_confirmed(key);
+            break;
+        case STATE_OPEN:
+            handle_input_confirmed(key);
+            break;
+        default:
+            buzz_invalid_input();
+    }
+}
+
+bool any_selected(void) {
+    return count_a + count_b + count_c + count_d > 0;
+}
+
+static void door_opened_handler(void) {
+    if (current_state != STATE_CONFIRMED && current_state != STATE_UNLOCKED) {
+        transition(STATE_UNAUTHORIZED);
+    } else {
+        transition(STATE_OPEN);
+    }
+
+    door_open = true;
+}
+
+static void door_closed_handler(void) {
+    reset_amounts();
+    transition(STATE_IDLE);
+
+    door_open = false;
+}
+
+void buzz_invalid_input(void) {
+    // FIXME: Implement this later
+}
+
+void sound_alarm(void) {
+    // FIXME: Implement this later
+}
+
+void reset_alarm(void) {
+    // FIXME: Implement this later
+}
+
+void transition(State_t state) {
+    state_chg = true;
+    current_state = state;
+}
+
+void sm_init(void) {
+    keypad_init(keypad_handler);
+    door_init(door_opened_handler, door_closed_handler);
+
+    ui_draw_idle();
+}
+
+void sm_loop(void) {
+    for (;;) {
+        __bis_SR_register(LPM0_bits | GIE);  /* Enter LPM0 with interrupts enabled */
+        __no_operation();
+
+        handle_general_interrupt();
+    }
+}
+
+void handle_general_interrupt(void) {
+    if (state_chg) {
+        switch (current_state) {
+            case STATE_IDLE:
+                ui_draw_idle();
+                break;
+            case STATE_SEL_COUNT:
+                ui_draw_sel_count();
+                break;
+            case STATE_CONFIRMED:
+                ui_draw_confirmed();
+                break;
+            case STATE_UNAUTHORIZED:
+                ui_draw_error();
+                break;
+            case STATE_OPEN:
+                ui_draw_open();
+                break;
+            case STATE_NONE_SELECTED:
+                ui_draw_none_selected();
+                break;
+            case STATE_RESET:
+                ui_draw_reset();
+                break;
+        }
+
+        state_chg = false;
+    }
+}
+
+
+char buffer_ab[16];
+char buffer_cd[16];
+
+void ui_draw_idle(void) {
+    lcd_clear();
+    lcd_set_cursor(0, 5);
+    lcd_print("Ready!");
+    lcd_set_cursor(1, 1);
+    lcd_print("Press A/B/C/D");
+}
+
+void ui_draw_sel_count(void) {
+    snprintf(buffer_ab, 17, "A:%c%4d B:%c%4d ",
+        selected_bev == BEV_A ? '*' : ' ',
+        count_a,
+        selected_bev == BEV_B ? '*' : ' ',
+        count_b
+    );
+    snprintf(buffer_cd, 17, "C:%c%4d D:%c%4d ",
+        selected_bev == BEV_C ? '*' : ' ',
+        count_c,
+        selected_bev == BEV_D ? '*' : ' ',
+        count_d
+    );
+
+    lcd_set_cursor(0, 0);
+    lcd_print(buffer_ab);
+    lcd_set_cursor(1, 0);
+    lcd_print(buffer_cd);
+}
+
+void ui_draw_confirmed(void) {
+    lcd_clear();
+    lcd_set_cursor(0, 3);
+    lcd_print("Confirmed!");
+    lcd_set_cursor(1, 1);
+    lcd_print("OPEN/[A-D]/[*]");
+}
+
+void ui_draw_error(void) {
+    lcd_clear();
+    lcd_set_cursor(0, 2);
+    lcd_print("UNAUTHORIZED");
+    lcd_set_cursor(1, 1);
+    lcd_print("CLOSE DOOR NOW");
+}
+
+void ui_draw_open(void) {
+    lcd_clear();
+    lcd_set_cursor(0, 2);
+    lcd_print("DOOR IS OPEN");
+    lcd_set_cursor(1, 0);
+    lcd_print("CLOSE /[A-D]/[*]");
+}
+
+void ui_draw_none_selected(void) {
+    lcd_clear();
+    lcd_set_cursor(0, 5);
+    lcd_print("SELECT");
+    lcd_set_cursor(1, 1);
+    lcd_print("ANY BEVERAGES!");
+
+    sleep(1000);
+
+    transition(STATE_SEL_COUNT);
+    ui_draw_sel_count();
+}
+
+void ui_draw_reset(void) {
+    lcd_clear();
+    lcd_set_cursor(0, 2);
+    lcd_print("AMOUNTS HAVE");
+    lcd_set_cursor(1, 3);
+    lcd_print("BEEN RESET");
+
+    sleep(1000);
+
+    if (door_open) {
+        transition(STATE_OPEN);
+        ui_draw_open();
+    } else {
+        transition(STATE_IDLE);
+        ui_draw_idle();
+    }
+}
\ No newline at end of file
diff --git a/src/state_machine.h b/src/state_machine.h
index 4017cb5..5742107 100644
--- a/src/state_machine.h
+++ b/src/state_machine.h
@@ -12,4 +12,33 @@
  * @date 2025-07-02
  */
 
-static void keypad_handler(char key);
\ No newline at end of file
+#ifndef STATE_MACHINE_H
+#define STATE_MACHINE_H
+
+static void keypad_handler(char key);
+
+void sm_init(void);
+
+void sm_loop(void);
+
+
+typedef enum {
+    STATE_IDLE,
+    STATE_SEL_COUNT,
+    STATE_CONFIRMED,
+    STATE_OPEN,
+    STATE_SECRET_INPUT,
+    STATE_UNLOCKED,
+    STATE_UNAUTHORIZED,
+    STATE_NONE_SELECTED,
+    STATE_RESET
+} State_t;
+
+typedef enum {
+    BEV_A,
+    BEV_B,
+    BEV_C,
+    BEV_D
+} SelectedBev_t;
+
+#endif // STATE_MACHINE_H
\ No newline at end of file
diff --git a/src/timer.c b/src/timer.c
new file mode 100644
index 0000000..10950cc
--- /dev/null
+++ b/src/timer.c
@@ -0,0 +1,41 @@
+#include <stdint.h>
+#include <msp430.h>
+#include <driverlib.h>
+#include "timer.h"
+
+/**
+ * @brief Führt eine blockierende Wartezeit aus.
+ * @param ms Zeit in Millisekunden
+ */
+void sleep(uint16_t ms) {
+    while (ms--) {
+        __bis_SR_register(LPM0_bits + GIE);
+        __no_operation();
+    }
+}
+
+void init_timer(void) {
+    static Timer_B_initUpModeParam param = {0};
+
+    param.clockSource = TIMER_B_CLOCKSOURCE_SMCLK;
+    param.clockSourceDivider = TIMER_B_CLOCKSOURCE_DIVIDER_1;
+    param.timerPeriod = 999;        // wenn 1000 Taktimpulse gezählt
+                                    // wurden, erfolgt ein Interrupt
+                                    // Periodendauer somit 1ms
+    param.timerInterruptEnable_TBIE =
+            TIMER_B_TBIE_INTERRUPT_DISABLE;         // no interrupt on 0x0000
+    param.captureCompareInterruptEnable_CCR0_CCIE =
+        TIMER_B_CAPTURECOMPARE_INTERRUPT_ENABLE;    // interrupt on TRmax
+    param.timerClear = TIMER_B_DO_CLEAR;
+    param.startTimer = true;
+
+    // start Timer:
+    Timer_B_initUpMode(TB0_BASE, &param);
+}
+
+// TimerB0 Interrupt Vector (TBxIV) handler
+#pragma vector=TIMER0_B0_VECTOR
+__interrupt void TIMER0_B0_ISR(void)
+{
+    __bic_SR_register_on_exit(LPM0_bits);
+}
diff --git a/src/timer.h b/src/timer.h
new file mode 100644
index 0000000..703f61e
--- /dev/null
+++ b/src/timer.h
@@ -0,0 +1,7 @@
+#ifndef TIMER_H
+#define TIMER_H
+
+void sleep(uint16_t ms);
+void init_timer(void);
+
+#endif // TIMER_H
\ No newline at end of file