diff --git a/hardware0.hpp b/hardware0.hpp
index 009241d..f8e7cf7 100644
--- a/hardware0.hpp
+++ b/hardware0.hpp
@@ -1,5 +1,4 @@
-#ifndef UART_HARDWARE_0_HPP
-#define UART_HARDWARE_0_HPP
+#pragma once
 
 #include <stdint.h>
 
@@ -82,8 +81,10 @@ constexpr int operator<<(const int &lhs, const ControlFlagsB0 &rhs) { return lhs
 constexpr int operator<<(const int &lhs, const ControlFlagsC0 &rhs) { return lhs << static_cast<int>(rhs); }
 // clang-format on
 
-extern void (*fnRx0IntHandler)();
-extern void (*fnDataReg0EmptyIntHandler)();
+#if defined(__AVR_ATmega328P__)
+#define USART0_RX_vect USART_RX_vect
+#define USART0_UDRE_vect USART_UDRE_vect
+#endif
 
 #else
 #error "This chip is not supported"
@@ -100,70 +101,56 @@ template <class cfg, Mode mode>
 class Hardware0<cfg, Driven::INTERRUPT, mode>
     : public detail::InterruptHardware<detail::Registers0, detail::ControlFlagsA0, detail::ControlFlagsB0,
                                        detail::ControlFlagsC0, cfg, mode> {
-	using detail::InterruptHardware<detail::Registers0, detail::ControlFlagsA0, detail::ControlFlagsB0,
-	                                detail::ControlFlagsC0, cfg, mode>::rxIntHandler;
-
-	using detail::InterruptHardware<detail::Registers0, detail::ControlFlagsA0, detail::ControlFlagsB0,
-	                                detail::ControlFlagsC0, cfg, mode>::dataRegEmptyIntHandler;
-
-	using HardwareImpl = detail::Hardware<detail::Registers0, detail::ControlFlagsA0, detail::ControlFlagsB0,
-	                                      detail::ControlFlagsC0, cfg, Driven::INTERRUPT, mode>;
-
   public:
 	static void init() FORCE_INLINE
 	{
-		detail::fnRx0IntHandler = rxIntHandler;
-		detail::fnDataReg0EmptyIntHandler = dataRegEmptyIntHandler;
-
 		HardwareImpl::init();
 		sei();
 	}
+
+  private:
+	using HardwareImpl = detail::Hardware<detail::Registers0, detail::ControlFlagsA0, detail::ControlFlagsB0,
+	                                      detail::ControlFlagsC0, cfg, Driven::INTERRUPT, mode>;
+
+	using InterruptHardwareImpl = detail::InterruptHardware<detail::Registers0, detail::ControlFlagsA0,
+	                                                        detail::ControlFlagsB0, detail::ControlFlagsC0, cfg, mode>;
+
+	// Must be friends with Uart interface to call these private handlers
+	template <class Driver>
+	friend class Uart;
+
+	static void rxIntHandler() FORCE_INLINE
+	{
+		InterruptHardwareImpl::rxIntHandler();
+	}
+
+	static void dataRegEmptyIntHandler() FORCE_INLINE
+	{
+		InterruptHardwareImpl::dataRegEmptyIntHandler();
+	}
 };
 
 } // namespace uart
 
-#undef FORCE_INLINE
-
-#endif
-
 //////////////////////////////////////////////////////////////////////////
 
-#ifdef UART0_INT_VECTORS
-
-#include <avr/interrupt.h>
-
-namespace uart {
-namespace detail {
-
-#if defined(__AVR_ATmega1284P__) || defined(__AVR_ATmega328P__)
-
-#if defined(__AVR_ATmega328P__)
-#define USART0_RX_vect USART_RX_vect
-#define USART0_UDRE_vect USART_UDRE_vect
-#endif
-
-void (*fnRx0IntHandler)() = nullptr;
-void (*fnDataReg0EmptyIntHandler)() = nullptr;
-
-ISR(USART0_RX_vect)
-{
-	if (fnRx0IntHandler)
-		fnRx0IntHandler();
+// Forward declare interrupt functions to allow adding them as friends
+extern "C" {
+void USART0_RX_vect() __attribute__((signal));
+void USART0_UDRE_vect() __attribute__((signal));
 }
 
-ISR(USART0_UDRE_vect)
-{
-	if (fnDataReg0EmptyIntHandler)
-		fnDataReg0EmptyIntHandler();
-}
+// clang-format off
+#define REGISTER_UART0_INT_VECTORS(uart_type) \
+	ISR(USART0_RX_vect)                       \
+	{                                         \
+		uart_type::rxIntHandler();            \
+	}                                         \
+	ISR(USART0_UDRE_vect)                     \
+	{                                         \
+		uart_type::dataRegEmptyIntHandler();  \
+	}                                         \
+	struct _##uart_type {}
+// clang-format on
 
-#else
-#error "This chip is not supported"
-#endif
-
-} // namespace detail
-} // namespace uart
-
-#undef UART0_INT_VECTORS
-
-#endif
+#undef FORCE_INLINE
diff --git a/hardware1.hpp b/hardware1.hpp
index 97b2b3a..22e4c15 100644
--- a/hardware1.hpp
+++ b/hardware1.hpp
@@ -1,5 +1,4 @@
-#ifndef UART_HARDWARE_1_HPP
-#define UART_HARDWARE_1_HPP
+#pragma once
 
 #include <stdint.h>
 
@@ -82,9 +81,6 @@ constexpr int operator<<(const int &lhs, const ControlFlagsB1 &rhs) { return lhs
 constexpr int operator<<(const int &lhs, const ControlFlagsC1 &rhs) { return lhs << static_cast<int>(rhs); }
 // clang-format on
 
-extern void (*fnRx1IntHandler)();
-extern void (*fnDataReg1EmptyIntHandler)();
-
 #define HAS_UART1
 
 #endif
@@ -102,65 +98,59 @@ template <class cfg, Mode mode>
 class Hardware1<cfg, Driven::INTERRUPT, mode>
     : public detail::InterruptHardware<detail::Registers1, detail::ControlFlagsA1, detail::ControlFlagsB1,
                                        detail::ControlFlagsC1, cfg, mode> {
-	using detail::InterruptHardware<detail::Registers1, detail::ControlFlagsA1, detail::ControlFlagsB1,
-	                                detail::ControlFlagsC1, cfg, mode>::rxIntHandler;
-
-	using detail::InterruptHardware<detail::Registers1, detail::ControlFlagsA1, detail::ControlFlagsB1,
-	                                detail::ControlFlagsC1, cfg, mode>::dataRegEmptyIntHandler;
-
-	using HardwareImpl = detail::Hardware<detail::Registers1, detail::ControlFlagsA1, detail::ControlFlagsB1,
-	                                      detail::ControlFlagsC1, cfg, Driven::INTERRUPT, mode>;
-
   public:
 	static void init() FORCE_INLINE
 	{
-		detail::fnRx1IntHandler = rxIntHandler;
-		detail::fnDataReg1EmptyIntHandler = dataRegEmptyIntHandler;
-
 		HardwareImpl::init();
 		sei();
 	}
+
+  private:
+	using HardwareImpl = detail::Hardware<detail::Registers1, detail::ControlFlagsA1, detail::ControlFlagsB1,
+	                                      detail::ControlFlagsC1, cfg, Driven::INTERRUPT, mode>;
+
+	using InterruptHardwareImpl = detail::InterruptHardware<detail::Registers1, detail::ControlFlagsA1,
+	                                                        detail::ControlFlagsB1, detail::ControlFlagsC1, cfg, mode>;
+
+	// Must be friends with Uart interface to call these private handlers
+	template <class Driver>
+	friend class Uart;
+
+	static void rxIntHandler() FORCE_INLINE
+	{
+		InterruptHardwareImpl::rxIntHandler();
+	}
+
+	static void dataRegEmptyIntHandler() FORCE_INLINE
+	{
+		InterruptHardwareImpl::dataRegEmptyIntHandler();
+	}
 };
 
-#endif
-
 } // namespace uart
 
-#undef FORCE_INLINE
-
-#endif
-
 //////////////////////////////////////////////////////////////////////////
 
-#ifdef UART1_INT_VECTORS
-
-#include <avr/interrupt.h>
-
-namespace uart {
-namespace detail {
-
-#if defined(__AVR_ATmega1284P__)
-
-void (*fnRx1IntHandler)() = nullptr;
-void (*fnDataReg1EmptyIntHandler)() = nullptr;
-
-ISR(USART1_RX_vect)
-{
-	if (fnRx1IntHandler)
-		fnRx1IntHandler();
+// Forward declare interrupt functions to allow adding them as friends
+extern "C" {
+void USART1_RX_vect() __attribute__((signal));
+void USART1_UDRE_vect() __attribute__((signal));
 }
 
-ISR(USART1_UDRE_vect)
-{
-	if (fnDataReg1EmptyIntHandler)
-		fnDataReg1EmptyIntHandler();
-}
+// clang-format off
+#define REGISTER_UART1_INT_VECTORS(uart_type) \
+	ISR(USART1_RX_vect)                       \
+	{                                         \
+		uart_type::rxIntHandler();            \
+	}                                         \
+	ISR(USART1_UDRE_vect)                     \
+	{                                         \
+		uart_type::dataRegEmptyIntHandler();  \
+	}                                         \
+	struct _##uart_type {                     \
+	}
+// clang-format off
 
 #endif
 
-} // namespace detail
-} // namespace uart
-
-#undef UART1_INT_VECTORS
-
-#endif
+#undef FORCE_INLINE
diff --git a/uart.hpp b/uart.hpp
index f840d90..a35dcb6 100644
--- a/uart.hpp
+++ b/uart.hpp
@@ -5,9 +5,7 @@
 #include "config.hpp"
 #include "software.hpp"
 
-#undef UART0_INT_VECTORS
 #include "hardware0.hpp"
-#undef UART1_INT_VECTORS
 #include "hardware1.hpp"
 
 #include "../flash/flash.hpp"
@@ -356,6 +354,25 @@ class Uart {
 	{
 		static_assert(type::always_false_v<Ts...>, "Not implemented");
 	}
+
+  private:
+	friend void ::USART0_RX_vect();
+	friend void ::USART0_UDRE_vect();
+
+#ifdef HAS_UART1
+	friend void ::USART1_RX_vect();
+	friend void ::USART1_UDRE_vect();
+#endif
+
+	static void rxIntHandler() FORCE_INLINE
+	{
+		Driver::rxIntHandler();
+	}
+
+	static void dataRegEmptyIntHandler() FORCE_INLINE
+	{
+		Driver::dataRegEmptyIntHandler();
+	}
 };
 
 template <typename cfg = Config<>>