changed names to more appropriate meaning

src/driver/i2c.c

@@ -46,16 +46,16 @@ void i2c_init() {
     (0x0 << USICNT0)
   );
   // flip the ports to input mode so we can enable pullup resistors on the next line
-  i2c_bus &= ~_BV(i2c_sda);
-  i2c_bus &= ~_BV(i2c_scl);
+  i2c_ddr &= ~_BV(i2c_sda);
+  i2c_ddr &= ~_BV(i2c_scl);
 
   // set both pins to HIGH to enable pullup.
   i2c_port |= _BV(i2c_sda);
   i2c_port |= _BV(i2c_scl);
 
   // flip the ports to output mode
-  i2c_bus |= _BV(i2c_sda);
-  i2c_bus |= _BV(i2c_scl);
+  i2c_ddr |= _BV(i2c_sda);
+  i2c_ddr |= _BV(i2c_scl);
 }
 
 /**
@@ -147,10 +147,10 @@ unsigned char i2c_write_byte(unsigned char data) {
   transfer(STATUS_CLOCK_8_BITS);
 
   // change data pin to input
-  i2c_bus &= ~_BV(i2c_sda);
+  i2c_ddr &= ~_BV(i2c_sda);
   unsigned char nack = transfer(STATUS_CLOCK_1_BIT);
   // change back to output
-  i2c_bus |= _BV(i2c_sda);
+  i2c_ddr |= _BV(i2c_sda);
   return nack;
 }
 
@@ -168,10 +168,10 @@ unsigned char i2c_read_byte(bool ack) {
     response = 0x00;
   }
   // change data pin to input
-  i2c_bus &= ~_BV(i2c_sda);
+  i2c_ddr &= ~_BV(i2c_sda);
   unsigned char data = transfer(STATUS_CLOCK_8_BITS);
   // change back to output
-  i2c_bus |= _BV(i2c_sda);
+  i2c_ddr |= _BV(i2c_sda);
   // send n/ack
   i2c_data = response;
   transfer(STATUS_CLOCK_1_BIT);

src/driver/i2c.h

@@ -19,8 +19,8 @@
   #define T4_TWI 4 // >4.0microseconds
 #endif
 
-#ifndef i2c_bus
-  #define i2c_bus DDRB
+#ifndef i2c_ddr
+  #define i2c_ddr DDRB
 #endif
 #ifndef i2c_port
   #define i2c_port PORTB
@@ -51,6 +51,7 @@ void i2c_init();
 
 /**
  * Send start command.
+ * @return True if the start successfully initiated, False otherwise.
  */
 bool i2c_start();