// This code is based on hello.ftdi.45.echo.ino programmed by Neil Gershenfeld
//
//
// tiny45 echo hello-world
//    9600 baud FTDI interface
//
// Neil Gershenfeld 11/17/19
//
// This work may be reproduced, modified, distributed,
// performed, and displayed for any purpose, but must
// acknowledge this project. 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 102 // 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 serial_port PORTB
#define serial_direction DDRB
#define serial_pins PINB
#define serial_pin_in(1 << PB2)
#define serial_pin_out(1 << PB1)
#define max_buffer 25

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);
}

const int BUTTON = 4;
const int LED = 3;
int BUTTONstate = 0;

void setup() {
  //
  // 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);
  pinMode(BUTTON, INPUT_PULLUP);
  pinMode(LED, OUTPUT);

}

static int index = 0;
static char chr;
char buffer[max_buffer] = {
  0
};

void loop() {
  //
  // main loop
  //

  BUTTONstate = digitalRead(BUTTON);
  if (BUTTONstate == HIGH) {
    digitalWrite(LED, HIGH);
    put_string( & serial_port, serial_pin_out, "1 \n");

  } else {
    digitalWrite(LED, LOW);
  }

}