* optimisation: -C3 compiler flag for optimised size

* bugfix: correct order of setting `DDRn` and `PORTn`
* optimisation: `enum` and `static const` instead of macros
* optimisation: `PT6302_startup` is now `inline`
* optimisation: functions are now static
* bugfix: `data` is now rotated and stored instead of just rotating
* special thanks to @kissadamfkut for pointing all of this out to me

PT6302.c

@@ -5,42 +5,3 @@
 #include <util/delay.h>
 #include "PT6302.h"
 
-void PT6302_startup (void)
-{
-  PORTB |= (CSBpin | CLKBpin);
-  PORTB &= ~DINpin;
-  PORTC |= RSTpin;
-  DDRB |= (CSBpin | CLKBpin | DINpin);
-  DDRC |= RSTpin;
-  _delay_us (TPRZ);
-  PORTC &= ~RSTpin;
-  _delay_us (TWRSTB);
-};
-
-void transmit_bytes (const uint8_t *payload, const uint8_t size)
-{
-  PORTB &= ~CSBpin;
-  for (int i = 0; i < size; ++i)
-    {
-      uint8_t data = payload[i];
-      for (int j = 0; j < 8; ++j)
-        {
-          PORTB &= ~CLKBpin;
-          if ((data & 0x01) == 0)
-            {
-              PORTB |= DINpin;
-            }
-          else
-            {
-              PORTB &= ~DINpin;
-            }
-          _delay_us (TCW);
-          PORTB |= CLKBpin;
-          _delay_us (TCW);
-          data >> 1;
-        }
-      _delay_us (TDOFF);
-    }
-  _delay_us (DTCSH);
-  PORTB |= CSBpin;
-}