diff --git a/io.hpp b/io.hpp
index 9112c1f..ccdec66 100644
--- a/io.hpp
+++ b/io.hpp
@@ -131,16 +131,13 @@ The following works in avr-gcc 5.4.0, but is not legal C++, because ptr's are no
   constexpr auto *foo = ptr;
 
 Workaround is to store the the address of the ptr in a uintptr_t and reinterpret_cast it at call site
-For this to work we need to temporarily disable the _SFR_IO8 macro so that the register macro just gives the address
+For this the sfr_defs.h provides a macro which returns the address of a register
 */
 
-#undef _SFR_IO8
-#define _SFR_IO8
-
 #ifdef PORT_A_AVAILABLE
-static constexpr uintptr_t PORT_A_DIR_REG_ADDR = DDRA + __SFR_OFFSET;
-static constexpr uintptr_t PORT_A_OUTPUT_REG_ADDR = PORTA + __SFR_OFFSET;
-static constexpr uintptr_t PORT_A_INPUT_REG_ADDR = PINA + __SFR_OFFSET;
+static constexpr uintptr_t PORT_A_DIR_REG_ADDR = _SFR_ADDR(DDRA);
+static constexpr uintptr_t PORT_A_OUTPUT_REG_ADDR = _SFR_ADDR(PORTA);
+static constexpr uintptr_t PORT_A_INPUT_REG_ADDR = _SFR_ADDR(PINA);
 #else
 static constexpr uintptr_t PORT_A_DIR_REG_ADDR = 0;
 static constexpr uintptr_t PORT_A_OUTPUT_REG_ADDR = 0;
@@ -148,9 +145,10 @@ static constexpr uintptr_t PORT_A_INPUT_REG_ADDR = 0;
 #endif
 
 #ifdef PORT_B_AVAILABLE
-static constexpr uintptr_t PORT_B_DIR_REG_ADDR = DDRB + __SFR_OFFSET;
-static constexpr uintptr_t PORT_B_OUTPUT_REG_ADDR = PORTB + __SFR_OFFSET;
-static constexpr uintptr_t PORT_B_INPUT_REG_ADDR = PINB + __SFR_OFFSET;
+
+static constexpr uintptr_t PORT_B_DIR_REG_ADDR = _SFR_ADDR(DDRB);
+static constexpr uintptr_t PORT_B_OUTPUT_REG_ADDR = _SFR_ADDR(PORTB);
+static constexpr uintptr_t PORT_B_INPUT_REG_ADDR = _SFR_ADDR(PINB);
 #else
 static constexpr uintptr_t PORT_B_DIR_REG_ADDR = 0;
 static constexpr uintptr_t PORT_B_OUTPUT_REG_ADDR = 0;
@@ -158,9 +156,9 @@ static constexpr uintptr_t PORT_B_INPUT_REG_ADDR = 0;
 #endif
 
 #ifdef PORT_C_AVAILABLE
-static constexpr uintptr_t PORT_C_DIR_REG_ADDR = DDRC + __SFR_OFFSET;
-static constexpr uintptr_t PORT_C_OUTPUT_REG_ADDR = PORTC + __SFR_OFFSET;
-static constexpr uintptr_t PORT_C_INPUT_REG_ADDR = PINC + __SFR_OFFSET;
+static constexpr uintptr_t PORT_C_DIR_REG_ADDR = _SFR_ADDR(DDRC);
+static constexpr uintptr_t PORT_C_OUTPUT_REG_ADDR = _SFR_ADDR(PORTC);
+static constexpr uintptr_t PORT_C_INPUT_REG_ADDR = _SFR_ADDR(PINC);
 #else
 static constexpr uintptr_t PORT_C_DIR_REG_ADDR = 0;
 static constexpr uintptr_t PORT_C_OUTPUT_REG_ADDR = 0;
@@ -168,18 +166,15 @@ static constexpr uintptr_t PORT_C_INPUT_REG_ADDR = 0;
 #endif
 
 #ifdef PORT_D_AVAILABLE
-static constexpr uintptr_t PORT_D_DIR_REG_ADDR = DDRD + __SFR_OFFSET;
-static constexpr uintptr_t PORT_D_OUTPUT_REG_ADDR = PORTD + __SFR_OFFSET;
-static constexpr uintptr_t PORT_D_INPUT_REG_ADDR = PIND + __SFR_OFFSET;
+static constexpr uintptr_t PORT_D_DIR_REG_ADDR = _SFR_ADDR(DDRD);
+static constexpr uintptr_t PORT_D_OUTPUT_REG_ADDR = _SFR_ADDR(PORTD);
+static constexpr uintptr_t PORT_D_INPUT_REG_ADDR = _SFR_ADDR(PIND);
 #else
 static constexpr uintptr_t PORT_D_DIR_REG_ADDR = 0;
 static constexpr uintptr_t PORT_D_OUTPUT_REG_ADDR = 0;
 static constexpr uintptr_t PORT_D_INPUT_REG_ADDR = 0;
 #endif
 
-#undef _SFR_IO8
-#define _SFR_IO8(io_addr) _MMIO_BYTE((io_addr) + __SFR_OFFSET)
-
 static constexpr auto getBus(const P pin)
 {
 	// Upper 4 bits of pin encode which port this pin is on