diff --git a/i2c.c b/i2c.c
index cd1cfad..234752d 100644
--- a/i2c.c
+++ b/i2c.c
@@ -27,6 +27,7 @@
 #include <avr/io.h>
 #include <avr/interrupt.h>
 #include <util/twi.h>
+#include "pinio.h"
 
 
 #if defined I2C_MASTER_MODE && defined I2C_SLAVE_MODE
@@ -94,8 +95,10 @@ void i2c_init(uint8_t address) {
 
   #ifdef I2C_MASTER_MODE
     #ifdef I2C_ENABLE_PULLUPS
-      I2C_DDR &= ~((1 << I2C_SCL_PIN) | (1 << I2C_SDA_PIN));
-      I2C_PORT |= (1 << I2C_SCL_PIN) | (1 << I2C_SDA_PIN);
+      SET_INPUT(SCL);
+      PULLUP_ON(SCL);
+      SET_INPUT(SDA);
+      PULLUP_ON(SDA);
     #endif /* I2C_ENABLE_PULLUPS */
 
     /**
diff --git a/i2c.h b/i2c.h
index e34d3f9..e484b80 100644
--- a/i2c.h
+++ b/i2c.h
@@ -12,25 +12,23 @@
 // Uncomment if we use EEPROM chips.
 //#define I2C_EEPROM_SUPPORT
 
+// Bus speed. Maximum is said to be 400000.
 #define I2C_BITRATE                 100000
-#define I2C_PORT                    PORTC
-#define I2C_DDR                     DDRC
-
-#define I2C_SCL_PIN                 0
-#define I2C_SDA_PIN                 1
+// Comment out if there are external pullups.
 #define I2C_ENABLE_PULLUPS
 
 #define I2C_BUFFER_SIZE             4
-#ifdef I2C_EEPROM_SUPPORT
-  // Depends on EEPROM type, usually it is 1 or 2 bytes.
-  #define I2C_PAGE_ADDRESS_SIZE     2
-#endif /* I2C_EEPROM_SUPPORT */
 
 #ifdef I2C_SLAVE_MODE
   #define I2C_SLAVE_RX_BUFFER_SIZE  1
   #define I2C_SLAVE_TX_BUFFER_SIZE  1
 #endif /* I2C_SLAVE_MODE */
 
+#ifdef I2C_EEPROM_SUPPORT
+  // Depends on EEPROM type, usually it is 1 or 2 bytes.
+  #define I2C_PAGE_ADDRESS_SIZE     2
+#endif /* I2C_EEPROM_SUPPORT */
+
 
 void i2c_init(uint8_t address);
 void i2c_send(uint8_t address, uint8_t* block, uint8_t tx_len);