/* IMPORTANT: I don't know if it's necessary, but I put 10k resistors on
 * the transmit and receive pins of the pic, just to be safe, and it works fine.
 */

/*                   PIC16F84
 *                 .-----------.
 *                -|RA2     RA1|- TRANSMIT white
 *                -|RA3     RA0|- 
 *                -|RA4    OSC1|- XT CLOCK pin1, 27pF to GND
 *    PUSH BUTTON -|MCLR   OSC2|- XT CLOCK pin2, 27pF to GND
 *            GND -|Vss     Vdd|- +5v
 * orange RECEIVE -|RB0     RB7|- 
 *                -|RB1     RB6|- 
 *                -|RB2     RB5|- 
 *                -|RB3     RB4|- 
 *                 '-----------'       
 *
 *  PUSH BUTTON = PIN - BUTTON - GND
 *                PIN - 10k - +5v  
 */

/*  rs232 interface (serial port communications) without a level converter.
 *  Therefore microcontroller pins are connected DIRECTLY to the serial cable.
 *  Therefore inverted (from standard) logic is used.
 *  
 *  PIC PIN18 PORTA1 - TRANSMIT (receive at PC end of serial cable) white
 *  PIC PIN06 PORTB0 - RECEIVE (transmit at PC end of serial cable) orange
 */

/*  looking head on at the female connector of a serial mouse coard:
 *  i.e. the end that plugs into your pc
 *
 *  5 4 3 2 1      =      blue    null    orange      white    null
 *   9 8 7 6       =          null    null      yellow     null
 *
 *  the following are loose wires on the other end of the coard.
 *  i.e. where it would have been soldered to the mouse circuit board.
 *
 *  5 = blue   = gnd = GND
 *  3 = orange = td  = PIC PIN06 PORTB0
 *  2 = white  = rd  = PIC PIN18 PORTA1
 *  7 = yellow = rts = unused
 */

#include <pic.h>
#include "rs232.c"

__CONFIG(WDTDIS & XT & UNPROTECT);

main(void) 
{
  TRISA = 0b00000000;
  TRISB = 0b00000001;
  PORTA = 0;
  PORTB = 0;

  rs232_initialize();

  rs232_send_string("Hello: ");
  for (;;) 
  {
    rs232_echo_char();
  }
}