Converting Arduino code to native C can be tricky. Here are some tips.

Digital I/O

In your arduino code you use "digitalWrite()" to control output bits. This does not exist in the "native" C environment we are now using.

For example you would use:

  digitalWrite( 13, HIGH);    // turn on LED
  digitalWrite( 13, LOW);     // turn off LED

This sets pin 13 on the Arduino board to a '1' (which also has the LED).

In the native C environment, first of all you do not use pin numbers, but names such as PB0, PB1 etc. These you will see for the Arduino on the typical pinout diagram (yellow boxes): ​uno.jpg

In the code you would use the following:

  PORTB |= _BV( PB5);      // turn on LED
  PORTB &= ~_BV( PB5);     // turn off LED

EXPERT NOTE: These idioms are recognized by the AVR code generator for GCC and generate the SBR and CBR machine instructions which are more efficient and safer than other more "obvious" ways of coding. In particular they do not depend on the current state of the register.

Also, setting the direction of the pins (input/output) is a bit different. In the Arduino environment you would use:

  pinMode( 13, OUTPUT);   // LED pin 13 is output

While in native C you would use:

  DDRB |= _BV( PB5);     // PB5 (LED) is output