diff --git a/prosjekt.X/command-handler.c b/prosjekt.X/command-handler.c
new file mode 100644
index 0000000..e9ade45
--- /dev/null
+++ b/prosjekt.X/command-handler.c
@@ -0,0 +1,158 @@
+#include "command-handler.h"
+
+// Initialize empty, global command context
+volatile command_context_t context = {UNKNOWN_COMMAND, SRC_NONE, FAN_NONE,
+                                      CNF_NONE};
+
+void parse_command(uint8_t command[], uint8_t command_len) {
+  ///////////////////////
+  // Command selection //
+  ///////////////////////
+
+  // Validate that we have a command
+  if (command_len < 1) {
+    context.command = UNKNOWN_COMMAND;
+  }
+
+  // Extract the first byte, which contains the command
+  uint8_t command_byte = command[0];
+
+  // Figure out which command to run
+  switch (command_byte) {
+  case 0x11: // Read config
+    context.command = READ_CONFIG;
+    break;
+  case 0x12: // Read voltage
+    context.command = READ_VOLTAGE;
+    break;
+  case 0x13: // Read temperature
+    context.command = READ_TERMPERATURE;
+    break;
+  case 0x14: // Read current fan speed
+    context.command = READ_FAN_SPEED;
+    break;
+  case 0x15: // Read bulk fan speed
+    context.command = READ_BULK_FAN_SPEED;
+    break;
+  case 0x21: // Write config
+    context.command = WRITE_CONFIG;
+    break;
+  case 0x22: // Clear stored fan speed data
+    context.command = CLEAR_BULK_FAN_SPEED;
+    break;
+  default: // Unrecognized command
+    context.command = UNKNOWN_COMMAND;
+    break;
+  }
+
+  ///////////////////////////////
+  // First parameter selection //
+  ///////////////////////////////
+
+  // Check if the command does not require a parameter. If it does not, return.
+  if (context.command == READ_TERMPERATURE) {
+    return;
+  }
+
+  // Validate that we have a first parameter, else requirements for command are
+  // not fulfilled. return unknown command.
+  if (command_len < 2) {
+    context.command = UNKNOWN_COMMAND;
+    return;
+  }
+
+  // Store the parameter
+  uint8_t param = command[1];
+
+  // Extract the parameter. Parameter is dependent on command
+  switch (command[0]) {
+  // Configuration parameters
+  case 0x11: // Read config
+  case 0x21: // Write config
+    // TODO: Handle parameters for config
+    break;
+
+  // Voltage parameters
+  case 0x12: // Read voltage
+    if (param == 0x01) {
+      context.src_voltage = SRC_INTERNAL;
+    } else if (param == 0x02) {
+      context.src_voltage = SRC_EXTRNAL;
+    } else if (param == 0x03) {
+      context.src_voltage = SRC_THERMISTOR;
+    } else {
+      context.src_voltage = SRC_NONE;
+    }
+    break;
+
+  // Fan parameters
+  case 0x14: // Read current fan speed
+  case 0x15: // Read bulk fan speed
+  case 0x22: // Clear stored fan speed data
+    context.command = READ_BULK_FAN_SPEED;
+    if (param == 0x01) {
+      context.fan = FAN1;
+    } else if (param == 0x02) {
+      context.fan = FAN2;
+    } else {
+      context.fan = FAN_NONE;
+    }
+    break;
+
+  // This should never be reached
+  default: // Unrecognized command
+    context.command = UNKNOWN_COMMAND;
+    break;
+  }
+
+  ////////////////////////////////
+  // Second parameter selection //
+  ////////////////////////////////
+
+  // Check if the command does not require a second parameter. If it does not,
+  // return. Only config write requires a second parameter.
+  if (context.command != WRITE_CONFIG) {
+    return;
+  }
+
+  // Validate that we have a first parameter, else requirements for command are
+  // not fulfilled. return unknown command.
+  if (command_len < 3) {
+    context.command = UNKNOWN_COMMAND;
+    return;
+  }
+
+  // Store the parameter
+  param = command[2];
+
+  // TODO: Handle the config parameters
+
+  // exit
+  return;
+}
+
+uint8_t route_command(int pos) {
+  switch (context.command) {
+  WRITE_CONFIG:
+    return WRITE_CONFIG;
+    break;
+  READ_CONFIG:
+    return READ_CONFIG;
+    break;
+  READ_VOLTAGE:
+    return READ_VOLTAGE;
+    break;
+  READ_TERMPERATURE:
+    return READ_TERMPERATURE;
+    break;
+  READ_FAN_SPEED:
+    return READ_FAN_SPEED;
+    break;
+  CLEAR_BULK_FAN_SPEED:
+    return CLEAR_BULK_FAN_SPEED;
+    break;
+  UNKNOWN_COMMAND:
+    return 0xFF;
+    break;
+  }
+}
diff --git a/prosjekt.X/command-handler.h b/prosjekt.X/command-handler.h
new file mode 100644
index 0000000..e09afda
--- /dev/null
+++ b/prosjekt.X/command-handler.h
@@ -0,0 +1,74 @@
+/*
+ * File:   command-handler.h
+ * Author: Sebastian H. Gabrielli
+ *
+ * Created on March 6, 2024, 12:43 PM
+ */
+
+#ifndef COMMAND_HANDLER_H
+#define COMMAND_HANDLER_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <avr/io.h>
+#include <stdint.h>
+#include <string.h>
+
+// Enum of all valid command types
+typedef enum {
+  WRITE_CONFIG,         // Change the configuration
+  READ_CONFIG,          // Read, and print the current configuration
+  READ_VOLTAGE,         // Read, and print a voltage
+  READ_TERMPERATURE,    // Read, and print the temperature
+  READ_FAN_SPEED,       // Read, and print the current fan speed
+  READ_BULK_FAN_SPEED,  // Read, and print the stored back fan speed data
+  CLEAR_BULK_FAN_SPEED, // Clear the buffer of stored fan speed data
+  UNKNOWN_COMMAND       // An unrecognized command has been sent
+} command_t;
+
+// Enum of all valid voltage sources
+typedef enum {
+  SRC_INTERNAL,   // Internal volage
+  SRC_EXTRNAL,    // External voltage
+  SRC_THERMISTOR, // Thermistor voltage
+  SRC_NONE        // No voltage source selected
+} src_voltage_t;
+
+// Enum of all valid config options
+// TODO: Move into config header file
+typedef enum {
+  CNF_NONE, // No config option
+} config_option_t;
+
+// Enum of all valid fans
+// TODO: Consider moving into it's own fan page
+typedef enum {
+  FAN1,    // The first fan
+  FAN2,    // The second fan
+  FAN_NONE // No fan
+} fans_t;
+
+// Struct with command context
+typedef struct {
+  command_t command;         // The command to execute
+  src_voltage_t src_voltage; // The selected voltage source
+  fans_t fan;                // The selected fan
+  config_option_t conf;      // The configuration option to cange
+                             // TODO: Add config value field for writing
+} command_context_t;
+
+// Parses the input string and outputs one of the valid commands
+void parse_command(uint8_t *command, uint8_t command_len);
+
+// Routes the provided command to the appropriate function to handle it
+// If the command is a read command it then returns the current byte.
+// The position is the byte to read when multiple bytes are being read.
+uint8_t route_command(int pos);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* COMMAND_HANDLER_H */
diff --git a/prosjekt.X/i2c.c b/prosjekt.X/i2c.c
new file mode 100644
index 0000000..c11fdcf
--- /dev/null
+++ b/prosjekt.X/i2c.c
@@ -0,0 +1,117 @@
+#include "i2c.h"
+#include "command-handler.h"
+
+// Basic I2C handling structure is heavily inspired by:
+// https://github.com/microchip-pic-avr-examples/avr128db48-bare-metal-twi-mplab/blob/master/twi-client.X/peripherals/TWI/TWI_client.c
+
+// We need to keep track of if the stop confition is in regards to a write or
+// read request
+volatile bool last_action_write = false;
+
+volatile uint8_t i2c_recv[I2C_RECV_BUF_SIZE] = {
+    0}; // Arbitrary length array to hold the received
+        // data, longer than max expected command
+volatile uint8_t i2c_recv_len = 0;
+
+void init_i2c(void) {
+  // Pin setup
+  PORTA.DIRSET = PIN2_bm | PIN3_bm;
+  PORTA.PINCTRLUPD = PIN2_bm | PIN3_bm;
+
+  // Enable operating in debug
+  TWI0.DBGCTRL = TWI_DBGRUN_bm;
+
+  // Initialize the control A register
+  TWI0.CTRLA = TWI_INPUTLVL_I2C_gc    // I2C voltage transition level
+               | TWI_SDASETUP_4CYC_gc // Four clock cycles setup time
+               | TWI_SDAHOLD_50NS_gc  // 50ns SDA hold time
+               | TWI_FMPEN_OFF_gc     // Standard SPI timing
+      ;
+
+  // The device's slave address
+  TWI0.SADDR = 0x42;
+
+  // Enable acting as a slave
+  TWI0.SCTRLA = TWI_DIEN_bm     // Enable data interrupt
+                | TWI_APIEN_bm  // Enable more interrupts
+                | TWI_PIEN_bm   // Enable stop flag interrupt
+                | PIN2_bm       // Respond to all TWI addresses
+                | TWI_ENABLE_bm // Enable acting as a slave
+      ;
+
+  // Reset the received stuff
+  i2c_reset_recv();
+}
+
+// Reset received counter and clear receive buffer
+void i2c_reset_recv() {
+  i2c_recv_len = 0;
+  for (int i = 0; i < I2C_RECV_BUF_SIZE; i++) {
+    i2c_recv[i] = 0;
+  }
+}
+
+void i2c_write_handler(uint8_t data) {
+  last_action_write = true;
+  i2c_recv[i2c_recv_len] = data;
+  i2c_recv_len++;
+}
+
+void i2c_read_handler() {
+  last_action_write = false;
+  TWI0.SDATA = route_command(i2c_recv_len);
+  i2c_recv_len++; // Increment the counter of the current amount of requests
+}
+
+void i2c_stop_handler() {
+  if (last_action_write) {
+    // Parse the received command data
+    parse_command(i2c_recv, i2c_recv_len);
+  }
+  // Reset the buffer for future transmissions
+  i2c_reset_recv();
+}
+
+// Address received
+ISR(TWI0_TWIS_vect) {
+  // Disable interrupts while handling I2C
+  cli();
+
+  // Check for the data interrupt flag
+  if (TWI0.SSTATUS & TWI_DIF_bm) {
+    uint8_t data = 0;
+
+    if (((TWI0.SSTATUS & TWI_DIR_bm) >> TWI_DIR_bp) == 0) {
+      // Data write Master -> Slave
+      data = TWI0.SDATA;
+
+      // Send the data to the write handler
+      i2c_write_handler(data);
+    } else {
+      // Data read Master <- Slave
+      i2c_read_handler();
+      // data = TWI0.SDATA;
+      // TWI0.SDATA = 1;
+    }
+
+    // Acknowledge having received
+    TWI0.SCTRLB = TWI_ACKACT_ACK_gc | TWI_SCMD_RESPONSE_gc;
+  }
+
+  // Check for address match or STOP
+  if (TWI0.SSTATUS & TWI_APIF_bm) {
+
+    if (TWI0.SSTATUS & TWI_AP_ADR_gc) {
+      // Address match, just send ack
+      TWI0.SCTRLB = TWI_ACKACT_ACK_gc | TWI_SCMD_RESPONSE_gc;
+    } else {
+      // STOP condition received
+      i2c_stop_handler();
+      // Send ACK
+      TWI0.SCTRLB = TWI_ACKACT_ACK_gc | TWI_SCMD_RESPONSE_gc;
+    }
+  }
+
+  // Re-enable interrupts
+  sei();
+}
diff --git a/prosjekt.X/i2c.h b/prosjekt.X/i2c.h
new file mode 100644
index 0000000..342f459
--- /dev/null
+++ b/prosjekt.X/i2c.h
@@ -0,0 +1,36 @@
+/*
+ * File:   i2c.h
+ * Author: sebgab
+ *
+ * Created on March 6, 2024, 1:53 PM
+ */
+
+#ifndef I2C_H
+#define I2C_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Include the IO for I2C
+#include "command-handler.h"
+#include "uart.h"
+#include <avr/interrupt.h>
+#include <avr/io.h>
+#include <stdbool.h>
+#include <util/twi.h>
+
+// Received data info
+#define I2C_RECV_BUF_SIZE 64
+
+// Reset recv to initial state
+void i2c_reset_recv();
+
+// Initialize the I2C bus
+void init_i2c(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* I2C_H */
diff --git a/prosjekt.X/main.c b/prosjekt.X/main.c
index 364a28b..80e332b 100644
--- a/prosjekt.X/main.c
+++ b/prosjekt.X/main.c
@@ -1,34 +1,38 @@
-/* 
+/*
  * File:   main.c
  * Author: Sebastian H. Gabrielli, Helle Augland Grasmo
  *
  * Created on March 6, 2024, 12:34 PM
  */
-#include "voltage.h"
 #include "uart.h"
+#include "voltage.h"
 #define RTC_PERIOD (511)
 #define DELAY_TIME 1000
-#include <avr/io.h>
-#include <avr/interrupt.h>
-#include <util/delay.h>
-#include <string.h>
-#include <stdbool.h>
-
-
 #include "eeprom.h"
+#include <avr/interrupt.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #define F_CPU 4E6
+#include "command-handler.h"
+#include "i2c.h"
 #include "uart.h"
+#include <avr/io.h>
 #include <util/delay.h>
 
 int main() {
-    ADC0_init();
-    init_uart((uint16_t)9600);
-    stdout = &USART_stream;
+  init_uart((uint16_t)9600);
+  init_i2c();
+  stdout = &USART_stream;
 
-    while (1) {
-        uint16_t adcVal = ADC0_read();
-        printf("The values: \n%u , %u\n",VREF_REFSEL_VDD_gc , adcVal);
-    }
-}
\ No newline at end of file
+  PORTB.DIRSET = PIN3_bm;
+
+  sei();
+
+  while (1) {
+    // uint16_t adcVal = ADC0_read();
+    // printf("The values: \n%u , %u\n",VREF_REFSEL_VDD_gc , adcVal);
+    ;
+  }
+}
diff --git a/prosjekt.X/nbproject/configurations.xml b/prosjekt.X/nbproject/configurations.xml
index 3b13f57..d9ab8f2 100644
--- a/prosjekt.X/nbproject/configurations.xml
+++ b/prosjekt.X/nbproject/configurations.xml
@@ -4,6 +4,8 @@
     <logicalFolder name="HeaderFiles"
                    displayName="Header Files"
                    projectFiles="true">
+      <itemPath>command-handler.h</itemPath>
+      <itemPath>i2c.h</itemPath>
       <itemPath>uart.h</itemPath>
       <itemPath>eeprom.h</itemPath>
       <itemPath>voltage.h</itemPath>
@@ -16,6 +18,8 @@
                    displayName="Source Files"
                    projectFiles="true">
       <itemPath>main.c</itemPath>
+      <itemPath>command-handler.c</itemPath>
+      <itemPath>i2c.c</itemPath>
       <itemPath>uart.c</itemPath>
       <itemPath>eeprom.c</itemPath>
       <itemPath>voltage.c</itemPath>
diff --git a/prosjekt.X/uart.h b/prosjekt.X/uart.h
index 7284552..9ca2621 100644
--- a/prosjekt.X/uart.h
+++ b/prosjekt.X/uart.h
@@ -20,7 +20,7 @@ extern "C" {
 #endif
     
 #define USART3_BAUD_RATE(BAUD_RATE) ((float)(F_CPU * 64 / (16 * (float)BAUD_RATE)) + 0.5)
-
+   
 // Initialize the USART3 controller
 void init_uart(uint16_t baud);