diff --git a/src/app/BoardConfig.cpp b/src/app/BoardConfig.cpp
new file mode 100644
index 0000000..a78096a
--- /dev/null
+++ b/src/app/BoardConfig.cpp
@@ -0,0 +1,17 @@
+#include "BoardConfig.h"
+
+BoardConfig::BoardConfig( const Pin ExternalInt,
+                          const Pin LDOEnable,
+                          const Pin BattVSensEnable,
+                          const Pin NRFCe,
+                          const Pin SwitchVSensEnable,
+                          const Pin NRFCs,
+                          const Pin MOSI,
+                          const Pin MISO,
+                          const Pin SCK,
+                          const Pin BattAnalogVSens,
+                          const Pin SwitchAnalogVSens
+):ExternalInt(ExternalInt), LDOEnable(LDOEnable), BattVSensEnable(BattVSensEnable), NRFCe(NRFCe), SwitchVSensEnable(SwitchVSensEnable), NRFCs(NRFCs), MOSI(MOSI), MISO(MISO), SCK(SCK), BattAnalogVSens(BattAnalogVSens), SwitchAnalogVSens(SwitchAnalogVSens)
+{
+  
+}
diff --git a/src/app/BoardConfig.h b/src/app/BoardConfig.h
new file mode 100644
index 0000000..104dfd8
--- /dev/null
+++ b/src/app/BoardConfig.h
@@ -0,0 +1,44 @@
+/**
+ * Author : Anatole SCHRAMM-HENRY
+ * Created the : 08/09/2022
+ * This class encapsulates the various configuration values for the board like the Pin Mapping for instance.
+ */
+#ifndef BOARDCONFIG_H
+#define BOARDCONFIG_H
+
+#include "definition.h"
+
+class BoardConfig
+{
+  public:
+    BoardConfig(
+    const Pin ExternalInt       = D2_EXTERNAL_INT,
+    const Pin LDOEnable         = D4_LDO_EN,
+    const Pin BattVSensEnable   = D5_BAT_V_SENS_EN,
+    const Pin NRFCe             = D6_NRF_CE,
+    const Pin SwitchVSensEnable = D7_SWITCH_V_SENS_EN,
+    const Pin NRFCs             = D10_NRF_CS,
+    const Pin MOSI              = D11_MOSI,
+    const Pin MISO              = D12_MISO,
+    const Pin SCK               = D13_SCK,
+    const Pin BattAnalogVSens   = A0_BAT_V_SENS,
+    const Pin SwitchAnalogVSens = A1_SWITCH_V_SENS
+    );
+
+    const Pin ExternalInt;
+    const Pin LDOEnable;
+    const Pin BattVSensEnable;
+    const Pin NRFCe;
+    const Pin SwitchVSensEnable;
+    const Pin NRFCs;               
+    const Pin MOSI;          
+    const Pin MISO;          
+    const Pin SCK;           
+    const Pin BattAnalogVSens;
+    const Pin SwitchAnalogVSens;
+    
+  protected:
+  private:
+};
+
+#endif //BOARDCONFIG_H
diff --git a/src/app/MBPeripherals.cpp b/src/app/MBPeripherals.cpp
new file mode 100644
index 0000000..a9e2665
--- /dev/null
+++ b/src/app/MBPeripherals.cpp
@@ -0,0 +1,109 @@
+#include "MBPeripherals.h"
+
+void defaultExtIntIsr(void){}
+
+MBPeripherals::MBPeripherals(const BoardConfig &boardConfig, void (*extIntIsr)(void)): _boardConfig(boardConfig), _NRF(boardConfig.NRFCe, boardConfig.NRFCs)
+{
+  if(!extIntIsr)
+    _extIntIsr = &(defaultExtIntIsr); //We provide a default ISR
+}
+
+uint8_t MBPeripherals::init()
+{
+  uint8_t toReturn(0);
+  //We initialize needed IOs :
+  pinMode(_boardConfig.ExternalInt, INPUT);
+  pinMode(_boardConfig.LDOEnable, OUTPUT);
+  _3V3PowerRail(OFF);
+  pinMode(_boardConfig.SwitchVSensEnable, INPUT_PULLUP);
+  pinMode(_boardConfig.BattVSensEnable, OUTPUT);
+  digitalWrite(_boardConfig.BattVSensEnable, LOW);
+  
+  //Unused pins are set as inputs with internal pullup enabled to reduce power consumption during sleep
+  pinMode(0,INPUT_PULLUP);
+  //pinMode(1,INPUT_PULLUP); TX pin for serial
+  pinMode(6,INPUT_PULLUP);
+  pinMode(7,INPUT_PULLUP);
+  pinMode(8,INPUT_PULLUP);
+  pinMode(9,INPUT_PULLUP);
+  pinMode(10,INPUT_PULLUP);
+  pinMode(11,INPUT_PULLUP);
+  pinMode(12,INPUT_PULLUP);
+  pinMode(A2,INPUT_PULLUP);
+  pinMode(A3,INPUT_PULLUP);
+  pinMode(A4,INPUT_PULLUP);
+  pinMode(A5,INPUT_PULLUP);
+  pinMode(A6,INPUT_PULLUP);
+  pinMode(A7,INPUT_PULLUP);
+
+  //We check that every external devices are responding
+  _3V3PowerRail(ON);
+  toReturn |= _NRF.begin();
+  _3V3PowerRail(OFF);
+
+  attachInterrupt(digitalPinToInterrupt(_boardConfig.ExternalInt), _extIntIsr, FALLING);
+
+  return toReturn;
+}
+
+uint8_t MBPeripherals::initExternalPeripherals(void)
+{
+  uint8_t toReturn(0);
+  
+  toReturn |= _NRF.begin();
+  
+  return toReturn;
+}
+
+float MBPeripherals::batteryVoltage(void)
+{
+  //We close the voltage divider bridge and we do the measurement
+  digitalWrite(_boardConfig.BattVSensEnable, HIGH);
+  int rawBatteryValue = analogRead(_boardConfig.BattAnalogVSens);
+  digitalWrite(_boardConfig.BattVSensEnable, LOW);
+  
+  return float(rawBatteryValue) * ADC_QUANTUM * VOLTAGE_DIV_COEFF; 
+}
+
+void MBPeripherals::_3V3PowerRail(State state)
+{
+  digitalWrite(_boardConfig.LDOEnable, state);
+  if(state) //We let some time for the voltage to stabilize on the rail. 
+    delay(10);
+}
+
+const RF24 &MBPeripherals::getRadio(void){return _NRF;}
+
+void MBPeripherals::applyRadioConfig(uint8_t channel, uint8_t paLevel, bool enableLNA, rf24_datarate_e datarate)
+{
+  _NRF.setChannel(channel);
+  _NRF.setPALevel(paLevel, enableLNA);
+  _NRF.setDataRate(datarate);
+}
+
+MAILBOX_EVENT_e MBPeripherals::readMailboxEvent(void)
+{
+  pinMode(_boardConfig.SwitchVSensEnable, OUTPUT);
+  digitalWrite(_boardConfig.SwitchVSensEnable, HIGH);
+  int analogValue = analogRead(_boardConfig.SwitchAnalogVSens);
+  digitalWrite(_boardConfig.SwitchVSensEnable, LOW);
+  pinMode(_boardConfig.SwitchVSensEnable, INPUT_PULLUP);
+
+  if(analogValue < 526)
+    return MAILBOX_EVENT_e::MAILBOX_LETTER;
+  else if(analogValue >= 526 && analogValue < 711)
+    return MAILBOX_EVENT_e::MAILBOX_PACKAGE;
+  else if(analogValue >= 711 && analogValue < 1000)
+    return MAILBOX_EVENT_e::MAILBOX_COLLECTED;
+  else return MAILBOX_EVENT_e::MAILBOX_UNKNOWN;
+}
+
+void MBPeripherals::maskExtInt(void)
+{
+  detachInterrupt(digitalPinToInterrupt(_boardConfig.ExternalInt));
+}
+
+void MBPeripherals::unmaskExtInt(void)
+{
+  attachInterrupt(digitalPinToInterrupt(_boardConfig.ExternalInt), _extIntIsr, FALLING);
+}
diff --git a/src/app/MBPeripherals.h b/src/app/MBPeripherals.h
new file mode 100644
index 0000000..2e9b335
--- /dev/null
+++ b/src/app/MBPeripherals.h
@@ -0,0 +1,79 @@
+/**
+ * Author : Anatole SCHRAMM-HENRY
+ * Created the : 08/09/2022
+ * This classe exposes all the methods necessary to init the MBPeripherals (Mail Box Peripherals) and 
+ * to retrieve various data and measurements like battery voltage, Mailbox events etc...
+ */
+#ifndef MBPERIPHERALS_H
+#define MBPERIPHERALS_H
+
+#include <RF24.h>
+#include <LowPower.h>
+ 
+#include "BoardConfig.h"
+
+void defaultExtIntIsr(void);
+
+class MBPeripherals
+{
+  public:
+    enum State {OFF, ON};
+  
+    MBPeripherals(const BoardConfig &boardConfig, void (*extIntIsr)(void) = nullptr);
+    /*
+     * Returns 1 if all the external devices are working properly, or an other value if it is not the case.
+     */
+    uint8_t init(void);
+    
+    /*
+     * After calling this methode , you need to execute initExternalPeripherals() to init the peripherals.
+     */
+    void externalPeripherals(State state){_3V3PowerRail(state);}
+
+    /*
+     * Used to init devices after each LDO powerup, external devices need to be turned one externalPeripherals(ON) before calling this function.
+     */
+    uint8_t initExternalPeripherals(void);
+    
+    /*
+     * Starts a battery voltage measurement and returns a float value in Volts.
+     */
+    float batteryVoltage(void);
+
+    /*
+     * Before calling this method, externalPeripherals(ON) and initExternalPeripherals() must be called respectively.
+     * This methods applies the NRF radio configuration.
+     */
+    void applyRadioConfig(uint8_t channel = RADIO_CHANNEL, uint8_t paLevel = RADIO_PA_LEVEL, bool enableLNA = ENABLE_LNA, rf24_datarate_e datarate = RADIO_DATARATE);
+    
+    /*
+     * Use this function just after the interrupt wake up retrieve the wake up event.
+     * Wake up event can be : MAILBOX_LETTER, MAILBOX_PACKAGE, MAILBOX_COLLECTED or MAILBOX_UNKNOWN.
+     */
+    MAILBOX_EVENT_e readMailboxEvent(void);
+
+    /*
+     * Disables wake up interrupts
+     */
+    void maskExtInt(void);
+
+    /*
+     * Enables wake up interrupts
+     */
+    void unmaskExtInt(void);
+    
+    /*
+     * Gets the NRF radio object to access it's api.
+     */
+    const RF24 &getRadio(void);
+    
+  protected:
+  private:
+    void _3V3PowerRail(State state);
+    const BoardConfig &_boardConfig;
+    const RF24 _NRF;
+    const void (*_extIntIsr)(void);
+  
+};
+
+#endif //MBPERIPHERALS_H
diff --git a/src/app/app.ino b/src/app/app.ino
new file mode 100644
index 0000000..fda8e44
--- /dev/null
+++ b/src/app/app.ino
@@ -0,0 +1,142 @@
+#include <Arduino.h>
+#include <LowPower.h>
+#include <SPI.h>
+#include "definition.h"
+#include "BoardConfig.h"
+#include "MBPeripherals.h"
+
+BoardConfig defaultBC;
+MBPeripherals MBP(defaultBC);
+
+MailboxDataPacket payload;
+uint8_t rCode(0);
+
+void setup()
+{
+  #if SERIAL_DEBUG_ENABLED 
+    Serial.begin(SERIAL_BAUD_RATE);
+    Serial.println("Setup begin");
+  #endif
+  
+  rCode = MBP.init();
+  memset(&payload, 0, sizeof payload);
+
+  #if SERIAL_DEBUG_ENABLED
+  Serial.print("Payload size : ");Serial.println(sizeof payload);
+  debugStruct(&payload);
+  #endif
+  payload.header = HEADER_e::CONNECTED_MAILBOX;
+
+  #if SERIAL_DEBUG_ENABLED
+  Serial.print("WSP init returned : ");Serial.println(rCode);
+  Serial.println("Setup end");
+  //Let time to the uart to spit out what's left
+  delay(100);
+  #endif
+
+  LowPower.powerDown(SLEEP_FOREVER, ADC_OFF, BOD_OFF);
+}
+
+void loop()
+{
+
+  MBP.maskExtInt();
+  if((payload.mailbox_event = MBP.readMailboxEvent()) != MAILBOX_EVENT_e::MAILBOX_UNKNOWN)
+  {
+    payload.battery = MBP.batteryVoltage();
+
+    //We now send the event
+    MBP.externalPeripherals(MBPeripherals::State::ON);
+    rCode = MBP.initExternalPeripherals();
+
+    #if SERIAL_DEBUG_ENABLED
+    Serial.print("MBP Ext Peripheral : "); Serial.println(rCode);
+    debugStruct(&payload);
+    #endif
+
+    if(MBP.getRadio().isChipConnected())
+    {
+      MBP.applyRadioConfig();
+      MBP.getRadio().setRetries(15, 15);
+      MBP.getRadio().openWritingPipe((const uint8_t *)RADIO_NODE_ADDRESS);
+      MBP.getRadio().stopListening(); //Very important, if not called, no ack will be received !
+
+      for(uint8_t i(0); i < MAX_SEND_ROUND_RETRIES; i++)
+      {
+        if(MBP.getRadio().write(&payload, sizeof payload))
+        {
+          #if SERIAL_DEBUG_ENABLED
+          Serial.println("Payload sent !");
+          delay(100);
+          #endif
+          break;
+        }
+        #if SERIAL_DEBUG_ENABLED
+        else
+        {
+          Serial.println("Failed to send payload !");
+          delay(100);
+        }
+        #endif
+      }
+    }
+    #if SERIAL_DEBUG_ENABLED
+    else
+    {
+      Serial.println("NRF missing !");
+      delay(100);
+    }
+    #endif
+
+    MBP.externalPeripherals(MBPeripherals::State::OFF);
+    
+    //We wait for some time before allowing next trigger
+    //Done to prevent switch bounces
+    LowPower.powerDown(SLEEP_2S, ADC_OFF, BOD_OFF);
+  }
+  #if SERIAL_DEBUG_ENABLED
+  else
+  {
+    Serial.println("Unknown event :O !");
+    delay(100);
+  }
+  #endif
+  
+  MBP.unmaskExtInt();
+  payload.id++;
+  //Sleep until next trigger happens
+  LowPower.powerDown(SLEEP_FOREVER, ADC_OFF, BOD_OFF);
+}
+
+void debugStruct(MailboxDataPacket *p)
+{
+  Serial.println("##############DATA##############");
+  Serial.print("ID : ");
+  Serial.println(p->id);
+
+  Serial.print("HEADER : ");
+  Serial.println(p->header);
+  
+  Serial.print("BATT : ");
+  Serial.print(p->battery);
+  Serial.println(" V");
+  
+  Serial.print("EVENT : ");
+  switch(p->mailbox_event)
+  {
+    case MAILBOX_LETTER:
+      Serial.println("LETTER");
+      break;
+    case MAILBOX_PACKAGE:
+      Serial.println("PACKAGE");
+      break;
+    case MAILBOX_COLLECTED:
+      Serial.println("COLLECTED");
+      break;
+    default:
+      Serial.println("UNKNOWN");
+      break;
+  }
+
+  delay(100); //Needed to prevent the micro to go to sleep to quickly and thus not sending the full serial output !
+}
diff --git a/src/app/definition.h b/src/app/definition.h
new file mode 100644
index 0000000..4ec2f6d
--- /dev/null
+++ b/src/app/definition.h
@@ -0,0 +1,63 @@
+/**
+ * Author : Anatole SCHRAMM-HENRY
+ * Created the : 08/09/2022
+ * This file contains all the config used by the other classes and sources files.
+ */
+#ifndef DEFINITION_H
+#define DEFINITION_H
+
+#include <Arduino.h>
+#include <RF24.h>
+#include "packet_format.h"
+
+//Serial debug config part
+#define SERIAL_DEBUG_ENABLED 0
+#define SERIAL_BAUD_RATE 115200
+
+//Battery config part
+#define ADC_QUANTUM 0.0033017578125 //ADC_VREF / ADC_RESOLUTION -> 3.314 and 10 bits (1024) in my case
+#define VOLTAGE_DIV_COEFF 1.321127673363577  //(R1 + R2)/R2
+
+//NRF Radio config part
+#define RADIO_CHANNEL 108 //0-125
+#define RADIO_NODE_ADDRESS "WEST1" //Weather Station 1 network because the mail box is connected on it
+#define RADIO_PA_LEVEL RF24_PA_MAX //RF24_PA_MIN,RF24_PA_LOW,RF24_PA_HIGH,RF24_PA_MAX
+#define ENABLE_LNA false //true or false
+#define RADIO_DATARATE RF24_250KBPS //Slow datarate to maximize range
+#define MAX_SEND_ROUND_RETRIES 5  //If no ACK is received, tries to resend a MAX_SEND_ROUND_RETRIES-1 more times
+                                  //Increase this parameter if the RF link is bad.
+
+//Pin config part
+typedef enum
+{
+  D2_EXTERNAL_INT = 2,
+  D4_LDO_EN = 4,
+  D5_BAT_V_SENS_EN = 5,
+  D6_NRF_CE = 6,
+  D7_SWITCH_V_SENS_EN = 7,
+  D10_NRF_CS = 10,
+  D11_MOSI = 11,
+  D12_MISO = 12,
+  D13_SCK = 13,
+  A0_BAT_V_SENS = A0,
+  A1_SWITCH_V_SENS = A1,
+} Pin;
+
+typedef enum
+{
+  MAILBOX_LETTER = 0,
+  MAILBOX_PACKAGE,
+  MAILBOX_COLLECTED,
+  MAILBOX_UNKNOWN,
+} MAILBOX_EVENT_e;
+
+//Payload structure
+typedef struct 
+{
+  uint16_t id;
+  HEADER_e header : 6;
+  float battery;
+  MAILBOX_EVENT_e mailbox_event;
+} __attribute__((__packed__)) MailboxDataPacket;
+
+#endif //DEFINITION_H
diff --git a/src/app/packet_format.h b/src/app/packet_format.h
new file mode 100644
index 0000000..a5e72a1
--- /dev/null
+++ b/src/app/packet_format.h
@@ -0,0 +1,6 @@
+#ifndef PACKET_FORMAT_H
+#define PACKET_FORMAT_H
+
+enum HEADER_e {WEATHER_STATION = 0, CONNECTED_MAILBOX};
+
+#endif //PACKET_FORMAT_H