diff --git a/app/include/app_transparent_client.hpp b/app/include/app_transparent_client.hpp
index fb428a9..3d3c96b 100644
--- a/app/include/app_transparent_client.hpp
+++ b/app/include/app_transparent_client.hpp
@@ -36,8 +36,23 @@ private:
   Utility::FunctionOwned<TransparentClient, void (radio::HwInstance*)> m_isr_cb_pointer;
   std::optional<radio::Interrupts> m_pending_irqs = std::nullopt;
 
+  enum class AppState
+  {
+    STARTUP,
+    PASSIVE,
+    ACTIVE_RX,
+    ACTIVE_TX,
+    RX_FRAME_READY
+  };
+
+  AppState m_state = AppState::STARTUP;
+
   void m_cbRadioIrqHandler(radio::HwInstance*);
-  void m_processInterrupts();
+  std::optional<AppState> m_hwInterruptToNewState();
+  void m_transitionToState(const AppState& new_state);
+  void m_processState();
+  void m_initiateTx();
+  bool m_txBufferIsReady();
 };
 
 }
diff --git a/app/src/app_transparent_client.cpp b/app/src/app_transparent_client.cpp
index 81ef9f0..599b0ae 100644
--- a/app/src/app_transparent_client.cpp
+++ b/app/src/app_transparent_client.cpp
@@ -5,6 +5,10 @@
 #include "radio_hw_instance.hpp"
 
 #include "app_transparent_client.hpp"
+#include "skullc_samd21_hal.hpp"
+#include "utility_logging.hpp"
+
+#include <utility_atomicscopeguard.hpp>
 
 namespace App
 {
@@ -14,7 +18,7 @@ TransparentClient::TransparentClient(const RadioSettings& initial_settings)
   , m_isr_cb_pointer(*this, &TransparentClient::m_cbRadioIrqHandler)
 {
   apply_settings(initial_settings);
-
+  m_radio->set_irq_handler(&m_isr_cb_pointer);
   m_radio->set_current_state(radio::HwInstance::States::PLL_ON);
 }
 
@@ -30,8 +34,21 @@ void TransparentClient::apply_settings(const RadioSettings& settings)
 
 void TransparentClient::process()
 {
-  if (m_pending_irqs)
-    m_processInterrupts();
+  std::optional<AppState> new_state_request = std::nullopt;
+
+  {
+    Utility::AtomicScopeGuard<Peripherals::Hal::Samd::StaticHal> irq_guard;
+    if (m_pending_irqs)
+      new_state_request = m_hwInterruptToNewState();
+  }
+
+  if (!new_state_request && m_txBufferIsReady())
+    new_state_request = AppState::ACTIVE_TX;
+
+  if (new_state_request)
+    m_transitionToState(*new_state_request);
+
+  m_processState();
 }
 
 void TransparentClient::m_cbRadioIrqHandler(radio::HwInstance*)
@@ -43,9 +60,86 @@ void TransparentClient::m_cbRadioIrqHandler(radio::HwInstance*)
     m_pending_irqs = new_irqs;
 }
 
-void TransparentClient::m_processInterrupts()
+std::optional<TransparentClient::AppState> TransparentClient::m_hwInterruptToNewState()
 {
+  const radio::Interrupts current_irqs = *m_pending_irqs;
   m_pending_irqs = std::nullopt;
+
+  SKULLC_LOG_DEBUG("APP: Processing IRQs: %d.", current_irqs);
+
+  const auto flag_is_set = [current_irqs](const radio::Interrupts& flag) -> bool
+    {
+      return std::underlying_type_t<radio::Interrupts>(current_irqs & flag);
+    };
+
+  switch (m_state)
+  {
+  case AppState::STARTUP:
+    if (flag_is_set(radio::Interrupts::PLL_LOCK))
+      return AppState::PASSIVE;
+    break;
+  case AppState::PASSIVE:
+    if (flag_is_set(radio::Interrupts::RX_START))
+      return AppState::ACTIVE_RX;
+    else if (flag_is_set(radio::Interrupts::AMI))
+      return AppState::RX_FRAME_READY;
+    break;
+  case AppState::ACTIVE_RX:
+    [[fallthrough]];
+  case AppState::ACTIVE_TX:
+    if (flag_is_set(radio::Interrupts::TRX_END))
+      return AppState::PASSIVE;
+    break;
+  default:
+    break;
+  }
+
+  return std::nullopt;
+}
+
+void TransparentClient::m_transitionToState(const AppState& new_state)
+{
+  SKULLC_LOG_DEBUG("APP: Trans. to state. %d -> %d.", m_state, new_state);
+
+  switch (m_state)
+  {
+  case AppState::STARTUP:
+    if (new_state == AppState::PASSIVE)
+      m_radio->set_current_state(radio::HwInstance::States::RX_ON);
+    break;
+  case AppState::PASSIVE:
+    // new_state == AppState::ACTIVE_RX is a HW transition. State machine simply locks itself.
+    // new_state == AppState::RX_FRAME_READY is handled in process state.
+    if (new_state == AppState::ACTIVE_TX)
+      m_initiateTx();
+    break;
+  case AppState::ACTIVE_RX:
+    // new_state == AppState::PASSIVE is a HW transition. State machine simply unlocks itself.
+    break;
+  case AppState::ACTIVE_TX:
+    if (new_state == AppState::PASSIVE)
+      m_radio->set_current_state(radio::HwInstance::States::RX_ON);
+    break;
+  case AppState::RX_FRAME_READY:
+    break;
+  }
+
+  m_state = new_state;
+}
+
+void TransparentClient::m_processState()
+{
+  return;
+}
+
+void TransparentClient::m_initiateTx()
+{
+  return;
+}
+
+bool TransparentClient::m_txBufferIsReady()
+{
+  return false;
 }
 
 }
diff --git a/main.cpp b/main.cpp
index 1a0c03d..5aec3b9 100644
--- a/main.cpp
+++ b/main.cpp
@@ -42,21 +42,19 @@ int main()
   const App::RadioSettings settings;
 
   m_app.setup(settings);
-  radio::HwInstance* radio_hw = radio::HwInstance::instance();
+
+  std::uint32_t counter = 0;
 
 	/* Replace with your application code */
 	while (true)
   {
-    gpio_toggle_pin_level(OUT_LED_RX);
+    if (counter++ == 1000)
+    {
+      gpio_toggle_pin_level(OUT_LED_TX);
+      counter = 0;
+    }
 
-    gpio_toggle_pin_level(OUT_LED_TX);
-
-    int16_t radio_status = radio_hw->register_read(radio::Registers::TRX_STATUS);
-    radio_status &= 0x1F;
-
-    SKULLC_LOG_INFO("Status: %d", radio_status);
-    SKULLC_LOG_INFO("Millis: %u", Hal::StaticHal::getMillis());
-
-    delay_ms(1000);
+    m_app->process();
+    Hal::StaticHal::delay(1);
 	}
 }
diff --git a/radio/src/radio_hw_instance.cpp b/radio/src/radio_hw_instance.cpp
index fdc749c..7593276 100644
--- a/radio/src/radio_hw_instance.cpp
+++ b/radio/src/radio_hw_instance.cpp
@@ -150,6 +150,7 @@ bool HwInstance::set_current_state(const States& new_state)
 
   register_write(Registers::TRX_STATE, std::uint8_t(new_state));
   m_wait_can_transition();
+  SKULLC_LOG_DEBUG("HW: New state. %d -> %d.", m_current_state, new_state);
   m_current_state = new_state;
   return true;
 }