//
//
// hello.ftdi.44.blink.c
//
// 115200 baud FTDI character echo, with flash string
//
// set lfuse to 0x5E for 20 MHz xtal
//
// Andrew Zuckerman
// 10/21/19
//
// Modified from hello.arduino.328P.blink.c:
// Neil Gershenfeld
// 10/21/13
//
// (c) Massachusetts Institute of Technology 2010
// This work may be reproduced, modified, distributed,
// performed, and displayed for any purpose. Copyright is
// retained and must be preserved. The work is provided
// as is; no warranty is provided, and users accept all 
// liability.
//

#include <avr/io.h>
#include <util/delay.h>

#define output(directions,pin) (directions |= pin) // set port direction for output
#define set(port,pin) (port |= pin) // set port pin
#define clear(port,pin) (port &= (~pin)) // clear port pin
#define led_delay() _delay_ms(100) // LED delay

#define led_port PORTA
#define led_direction DDRA
#define led_pin (1 << PA7)

int main(void) {
   //
   // main
   //
   // set clock divider to /1
   //
   CLKPR = (1 << CLKPCE);
   CLKPR = (0 << CLKPS3) | (0 << CLKPS2) | (0 << CLKPS1) | (0 << CLKPS0);
   //
   // initialize LED pins
   //
   clear(led_port, led_pin);
   output(led_direction, led_pin);
   //
   // main loop
   //
   while (1) {
      set(led_port, led_pin);
      led_delay();
      clear(led_port, led_pin);
      led_delay();
   }