//
//
// hello.light.44.c
//
// phototransistor + button + 2 LEDs
//    9600 baud FTDI interface
//
// Alex Berke
//
// Modified from code provided by Neil Gershenfeld
//
// (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 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 char_delay() _delay_ms(10) // char delay


// (Board specific)
// RX (serial output) connected to PA1
#define SERIAL_PORT PORTA
#define SERIAL_DIRECTION DDRA
#define SERIAL_PIN_OUT (1 << PA1)
// Button connected to PA0
#define BUTTON_PINS PINA
#define BUTTON_PORT PORTA
#define BUTTON_DIRECTION DDRA
#define BUTTON_PIN (1 << PA0)
// LED 1 connected to PB0
// LED 2 connected to PB1
#define LED_PORT PORTB
#define LED_DIRECTION DDRB
#define LED_PIN_1 (1 << PB0)
#define LED_PIN_2 (1 << PB1)


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 output
   //
   // Initialize serial pin (output)
   set(SERIAL_PORT, SERIAL_PIN_OUT);
   output(SERIAL_DIRECTION, SERIAL_PIN_OUT);
   // Initialize LED pins (output)
   clear(LED_PORT, LED_PIN_1);
   clear(LED_PORT, LED_PIN_2);
   output(LED_DIRECTION, LED_PIN_1);
   output(LED_DIRECTION, LED_PIN_2);
   
   //
   // Initialize input
   //
   // Initialize button pin (input)
   set(BUTTON_PORT, BUTTON_PIN); // Turn on internal pull-up resister
   input(BUTTON_DIRECTION, BUTTON_PIN);
   
   //
   // Initialize A/D
   //
   // Board specific: My phototransistor is connected on ADC2/PA2.
   ADMUX = (0 << REFS1) | (0 << REFS0) // Vcc ref
      | (0 << ADLAR) // right adjust
      | (0 << MUX3) | (0 << MUX2) | (1 << MUX1) | (0 << MUX0); // ADC2
   ADCSRA = (1 << ADEN) // enable
      | (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0); // prescaler /128


   static char chr;  // Used for serial

   // The light setting alternates between 3 settings:
   // 0: LED_1 off & LED_2 off
   // 1: LED_1 on & LED_2 off
   // 2: LED_1 on & LED_2 on
   int light_setting = 0;
   int button_state, last_button_state = 0;
   while (1) {
      //
      // main loop
      //
      //
      // Handle button and LEDs
      // check if button state has been toggled
      button_state = pin_test(BUTTON_PINS, BUTTON_PIN);
      if (button_state != last_button_state) {
         // the button has been toggled
         last_button_state = button_state; // Remember this for next loop.
         // if it is toggled unpressed, keep the settings as they are
         // otherwise, update the settings
         if (!button_state) {
            // Increment the light setting (modular 3 because there are 3 settings)
            light_setting = (light_setting + 1) % 3;

            if (light_setting == 0) {
               clear(LED_PORT, LED_PIN_1);
               clear(LED_PORT, LED_PIN_2);
            }
            if (light_setting == 1) {
               set(LED_PORT, LED_PIN_1);
               clear(LED_PORT, LED_PIN_2);
            }
            if (light_setting == 2) {
               set(LED_PORT, LED_PIN_1);
               set(LED_PORT, LED_PIN_2);
            }
         }
      }

      // Handle reading from phototransistor
      //
      // send framing
      //
      put_char(&SERIAL_PORT, SERIAL_PIN_OUT, 1);
      char_delay();
      put_char(&SERIAL_PORT, SERIAL_PIN_OUT, 2);
      char_delay();
      put_char(&SERIAL_PORT, SERIAL_PIN_OUT, 3);
      char_delay();
      put_char(&SERIAL_PORT, SERIAL_PIN_OUT, 4);
      char_delay();
      //
      // initiate conversion
      //
      ADCSRA |= (1 << ADSC);
      //
      // wait for completion
      //
      while (ADCSRA & (1 << ADSC));
      //
      // send result
      //
      // Send ADC low
      chr = ADCL;
      put_char(&SERIAL_PORT, SERIAL_PIN_OUT, chr);
      char_delay();
      // Send ADC high
      chr = ADCH;
      put_char(&SERIAL_PORT, SERIAL_PIN_OUT, chr);
      char_delay();
   }
}