//
//
// hello.button.45.c
//
// button hello-world
//    9600 baud FTDI interface
//
// Neil Gershenfeld
// 10/31/10
//
// (c) Massachusetts Institute of Technology 2010
// Permission granted for experimental and personal use;
// license for commercial sale available from MIT.
//

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

#define output(directions,pin) (directions |= pin) // set port direction for output
#define input(directions,pin) (directions &= (~pin)) // set port direction for input
#define set(port,pin) (port |= pin) // set port pin
#define clear(port,pin) (port &= (~pin)) // clear port pin
#define pin_test(pins,pin) (pins & pin) // test for port pin
#define bit_test(byte,bit) (byte & (1 << bit)) // test for bit set
#define bit_delay_time 100 // bit delay for 9600 with overhead
#define bit_delay() _delay_us(bit_delay_time) // RS232 bit delay
#define half_bit_delay() _delay_us(bit_delay_time/2) // RS232 half bit delay
#define sample_delay() _delay_ms(50) 

#define input_port PORTB
#define input_direction DDRB
#define input_pin4 (1 << PB4)
#define input_pin3 (1 << PB3)
#define input_pins PINB
#define serial_port PORTB
#define serial_direction DDRB
#define serial_pin_out (1 << PB2)

void put_char(volatile unsigned char *port, unsigned char pin, char txchar) {
   //
   // send character in txchar on port pin
   //    assumes line driver (inverts bits)
   //
   // start bit
   //
   clear(*port,pin);
   bit_delay();
   //
   // unrolled loop to write data bits
   //
   if bit_test(txchar,0)
      set(*port,pin);
   else
      clear(*port,pin);
   bit_delay();
   if bit_test(txchar,1)
      set(*port,pin);
   else
      clear(*port,pin);
   bit_delay();
   if bit_test(txchar,2)
      set(*port,pin);
   else
      clear(*port,pin);
   bit_delay();
   if bit_test(txchar,3)
      set(*port,pin);
   else
      clear(*port,pin);
   bit_delay();
   if bit_test(txchar,4)
      set(*port,pin);
   else
      clear(*port,pin);
   bit_delay();
   if bit_test(txchar,5)
      set(*port,pin);
   else
      clear(*port,pin);
   bit_delay();
   if bit_test(txchar,6)
      set(*port,pin);
   else
      clear(*port,pin);
   bit_delay();
   if bit_test(txchar,7)
      set(*port,pin);
   else
      clear(*port,pin);
   bit_delay();
   //
   // stop bit
   //
   set(*port,pin);
   bit_delay();
   //
   // char delay
   //
   bit_delay();
   }

int main(void) {
   //
   // main
   //
   // set clock divider to /1
   //
   CLKPR = (1 << CLKPCE);
   CLKPR = (0 << CLKPS3) | (0 << CLKPS2) | (0 << CLKPS1) | (0 << CLKPS0);
   //
   // initialize pins
   //
   set(serial_port, serial_pin_out);
   output(serial_direction, serial_pin_out);
   
   input(input_direction, input_pin4);
   set(input_port, input_pin4); // turn on pull-up
   
   input(input_direction, input_pin3);
   set(input_port, input_pin3); // turn on pull-up
   //
   // main loop
   //
   while (1) {

      while (0 == pin_test(input_pins,input_pin4) || 0 == pin_test(input_pins,input_pin3) ) {
         while (0 == pin_test(input_pins,input_pin4) && 0 == pin_test(input_pins,input_pin3) ) {
            sample_delay();
            put_char(&serial_port, serial_pin_out, 'u');
            }
         while (0 == pin_test(input_pins,input_pin4) && 0 != pin_test(input_pins,input_pin3) ) {
            sample_delay();
            put_char(&serial_port, serial_pin_out, 'r');
            }
         while (0 != pin_test(input_pins,input_pin4) && 0 == pin_test(input_pins,input_pin3) ) {
            sample_delay();
            put_char(&serial_port, serial_pin_out, 'l');
            }
         }
      sample_delay();
      put_char(&serial_port, serial_pin_out, 'd');

      }
   }