//
// hello.ftdi.44.echo.c
//
// 115200 baud FTDI character echo, with flash string
//
// set lfuse to 0x7E for 20 MHz xtal
//
// Neil Gershenfeld
// 12/8/10
//
// (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>
#include <avr/pgmspace.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 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 115200 with overhead
//102 for 9600, 8.5 for 115200
#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 PORTA
#define serial_direction DDRA
#define serial_pin_out (1 << PA4)
#define in_port PORTA
#define in_direction DDRA
#define in_pins PINA
#define x_pin (1 << PA2)
#define y_pin (1 << PA1)

#define NLOOP 3

#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);
   }

int main(void) {
   //
   // main
   //
   static unsigned char i;
   static uint16_t xoff, xon, yoff, yon;
   //
   // set clock divider to /1
   //
   CLKPR = (1 << CLKPCE);
   CLKPR = (0 << CLKPS3) | (0 << CLKPS2) | (0 << CLKPS1) | (0 << CLKPS0);
   //
   // initialize output pins
   //
   set(serial_port, serial_pin_out);
   output(serial_direction, serial_pin_out);
   //
   // main loop
   //
   while(1){
     
     xoff = 0;
     xon = 0;
     char buf[80];

     for (i = 0; i < NLOOP; ++i){
       
       while (0 == pin_test(in_pins, x_pin))
         ;
       while (0 != pin_test(in_pins, x_pin))
         ;
       
       while(0 == pin_test(in_pins, x_pin))
         xoff +=1;
       while (0 != pin_test(in_pins, x_pin))
         xon +=1;
     }



     yoff = 0;
     yon = 0;
     for (i = 0; i < NLOOP; ++i){
       while (0 == pin_test(in_pins, y_pin))
         ;
       while (0 != pin_test(in_pins, y_pin))
         ;
       while(0 == pin_test(in_pins, y_pin))
         yoff +=1;
       while (0 != pin_test(in_pins, y_pin))
         yon +=1;
     }
       
       /*put_char(&serial_port, serial_pin_out, 1);
       put_char(&serial_port, serial_pin_out, 2);
       put_char(&serial_port, serial_pin_out, 3);
       put_char(&serial_port, serial_pin_out, 4);
       */


       /*put_char(&serial_port, serial_pin_out, (xoff & 255));
       put_char(&serial_port, serial_pin_out, ((xoff >> 8) & 255));
       put_char(&serial_port, serial_pin_out, (xon & 255));
       put_char(&serial_port, serial_pin_out, ((xon >> 8) & 255));

       put_char(&serial_port, serial_pin_out, (yoff & 255));
       put_char(&serial_port, serial_pin_out, ((yoff >> 8) & 255));
       put_char(&serial_port, serial_pin_out, (yon & 255));
       put_char(&serial_port, serial_pin_out, ((yon >> 8) & 255));
       */
     sprintf(buf, "xoff: %d xon: %d yoff: %d yon: %d\n", 
         xoff, xon, yoff, yon);
     put_string(&serial_port, serial_pin_out, buf);


     /*put_string(&serial_port, serial_pin_out, "hello!");*/

     //_delay_us(100);
     }
   }