//
// laser-pointer.44.c
//
// button-controlled laser pointer and ftdi communication
//
// Daniel Windham
// 12/12/15
//
// adapted from
// Neil Gershenfeld
// 11/14/10
//
// (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>
#include <avr/pgmspace.h>

#define output(directions,pin) (directions |= pin) // set port direction for output
#define input(directions,pin) (directions &= ~pin) // set port direction for input
#define pullup(port,pin) (port |= pin) // set internal pullup on input pin
#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 103 // 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

#define serial_port PORTB
#define serial_direction DDRB
#define serial_pins PINB
#define serial_pin_in (1 << PB1)
#define serial_pin_out (1 << PB0)

#define laser_port PORTA // laser switch port
#define laser_direction DDRA // laser switch direction
#define laser_pin (1 << PA0) // laser mosfet switch pin

#define buttons_port PORTA // buttons port
#define buttons_pins PINA // buttons pin
#define buttons_direction DDRA // buttons direction
#define laser_button_pin (1 << PA1) // laser button pin
#define button_0_pin (1 << PA2) // general button pins
#define button_1_pin (1 << PA3) // "
#define button_2_pin (1 << PA4) // "

void get_char(volatile unsigned char *pins, unsigned char pin, char *rxbyte) {
  //
  // read character into rxbyte on pins pin
  //    assumes line driver (inverts bits)
  //
  *rxbyte = 0;
  while (pin_test(*pins,pin))
    //
    // wait for start bit
    //
    ;
  //
  // delay to middle of first data bit
  //
  half_bit_delay();
  bit_delay();
  //
  // unrolled loop to read data bits
  //
  if pin_test(*pins,pin)
    *rxbyte |= (1 << 0);
  else
    *rxbyte |= (0 << 0);
  bit_delay();
  if pin_test(*pins,pin)
    *rxbyte |= (1 << 1);
  else
    *rxbyte |= (0 << 1);
  bit_delay();
  if pin_test(*pins,pin)
    *rxbyte |= (1 << 2);
  else
    *rxbyte |= (0 << 2);
  bit_delay();
  if pin_test(*pins,pin)
    *rxbyte |= (1 << 3);
  else
    *rxbyte |= (0 << 3);
  bit_delay();
  if pin_test(*pins,pin)
    *rxbyte |= (1 << 4);
  else
    *rxbyte |= (0 << 4);
  bit_delay();
  if pin_test(*pins,pin)
    *rxbyte |= (1 << 5);
  else
    *rxbyte |= (0 << 5);
  bit_delay();
  if pin_test(*pins,pin)
    *rxbyte |= (1 << 6);
  else
    *rxbyte |= (0 << 6);
  bit_delay();
  if pin_test(*pins,pin)
    *rxbyte |= (1 << 7);
  else
    *rxbyte |= (0 << 7);
  //
  // wait for stop bit
  //
  bit_delay();
  half_bit_delay();
}

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();
}

void put_string(volatile unsigned char *port, unsigned char pin, char *str) {
  //
  // print a null-terminated string
  //
  static int index;
  index = 0;
  do {
    put_char(port, pin, str[index]);
    ++index;
  } while (str[index] != 0);
}

int main(void) {
  // set clock divider to /1
  CLKPR = (1 << CLKPCE);
  CLKPR = (0 << CLKPS3) | (0 << CLKPS2) | (0 << CLKPS1) | (0 << CLKPS0);

  // initialize laser pin
  set(laser_port, laser_pin);
  output(laser_direction, laser_pin);

  // initialize button pins
  input(buttons_direction, laser_button_pin);
  input(buttons_direction, button_0_pin);
  input(buttons_direction, button_1_pin);
  input(buttons_direction, button_2_pin);
  pullup(buttons_port, laser_button_pin);
  pullup(buttons_port, button_0_pin);
  pullup(buttons_port, button_1_pin);
  pullup(buttons_port, button_2_pin);

  // initialize serial pins
  set(serial_port, serial_pin_out);
  output(serial_direction, serial_pin_out);

  char buttons_state;

  while (1) {
    buttons_state = 0;

    // poll button states
    if (!pin_test(buttons_pins, button_0_pin)) {
      buttons_state |= 1 << 0;
    }
    if (!pin_test(buttons_pins, button_1_pin)) {
      buttons_state |= 1 << 1;
    }
    if (!pin_test(buttons_pins, button_2_pin)) {
      buttons_state |= 1 << 2;
    }

    // poll laser button state
    if (!pin_test(buttons_pins, laser_button_pin)) {
      buttons_state |= 1 << 3;
      set(laser_port, laser_pin);
    } else {
      clear(laser_port, laser_pin);
    }

    put_char(&serial_port, serial_pin_out, buttons_state);
  }
}