#include <dos.h>
#include <string.h>
#include "COMMDRV.H"

const unsigned INT        =  5;
const unsigned RECEIVE    =  0;
const unsigned TRANSMIT   =  0;
const unsigned L_DIVISOR  =  0;
const unsigned U_DIVISOR  =  1;
const unsigned INT_ENB    =  1;
const unsigned INT_ID     =  2;
const unsigned LINE_CTRL  =  3;
const unsigned MODEM_CTRL =  4;
const unsigned LINE_STAT  =  5;
const unsigned MODEM_STAT =  6;

static void near dummy (void) {}

// returns negation of contents of on-board 8253 counter
static unsigned near readtimer (void)
{
  asm pushf
  asm cli
  asm mov  al,0h
  asm out  43h,al
      dummy();
  asm in   al,40h
  asm mov  bl,al
      dummy();
  asm in   al,40h
  asm mov  bh,al
  asm not  bx
  asm popf
  return( _BX );
}

// computer independent delay used for timout purposes.
void comdelay( unsigned timer_ticks )
{
    unsigned long stop;
    unsigned cur, prev;

    stop = (prev = readtimer()) + (timer_ticks);

    while ((cur = readtimer()) < stop)
        {
        if (cur < prev)
            {
            if (stop < 0x10000L)
                break;
            stop -= 0x10000L;
            }
        prev = cur;
        }
}

void initCommCard(unsigned baseAddr, unsigned baudRate)
{
  unsigned divisor;

  // Oscillator frequency is 1.8432MHz, or 1,843,200 Hz
  // The divisor is calculated by dividing the frequency by 16, then dividing
  // again by the baudrate, or --- divisor = (f / 16) / baudrate
  // 1,843,200 / 16 is 115200, so -
  divisor = 115200 / baudRate;

  // tell card, we are about to set options
  outportb(baseAddr + LINE_CTRL, 0x80);

  // assign 16 bit AX register to our divisor, so we can load the
  // card with the low and high bytes of the divisor.
  _AX = divisor;
  outportb(baseAddr + L_DIVISOR, _AL);
  outportb(baseAddr + U_DIVISOR, _AH);

  // set the card the 7 bits of data, even parity and 1 stop bit
  outportb(baseAddr + LINE_CTRL, 0x1A);
  outportb(baseAddr + MODEM_CTRL, 0x00);

  // clear the receive buffer
  delay(50);
  inportb(baseAddr + RECEIVE);
  delay(50);
  inportb(baseAddr + RECEIVE);
}

void writePod(unsigned baseAddr, char message[255])
{
  unsigned char x, times;

  // get length of the string to send
  x = strlen(message);

  // set the card into transmit mode
  outportb(baseAddr + MODEM_CTRL, 0x0F);

  for (times = 0; times < x; times++)
    {
      // wait until the card is ready to transmit a character
      while ((inportb(baseAddr+LINE_STAT) & 0x20) == 0);

      // transmit the character
      outportb(baseAddr+TRANSMIT, message[times]);
    }

  // wait until the character is transmitted
  while ((inportb(baseAddr+LINE_STAT) & 0x20) == 0);

  // transmit a Carriage Return
  outportb(baseAddr+TRANSMIT, 0x0D);

  // wait until CR is transmitted
  while ((inportb(baseAddr+LINE_STAT) & 0x20) == 0);

  // wait for the card to come back
  while ((inportb(baseAddr+LINE_STAT) & 0x40) == 0);

  // place the card into receive mode
  outportb(baseAddr+MODEM_CTRL, 0x0D);
}

void readPod(unsigned baseAddr, char message[255])
{
  unsigned char x = 255, ch;
  char retstring[255] = "";
  unsigned int timeout;

  do
   {
     // character location in string is incremented
     x++;

     // timeout initialized
     timeout = 200;
     do
      {
        // decrement our timeout counter
        timeout--;
        // wait for 200 counter ticks
        comdelay(200);
        // wait until the card sees a character or until our counter has
        // timed out.
      } while ((timeout) && ((inportb(baseAddr+LINE_STAT) & 0x01) == 0x00));

      // if it has not timed out, store the character
      if (timeout != 0x00)
         retstring[x] = inportb(baseAddr + RECEIVE);
        // otherwise, return with an error message
        else {
                strcpy(message, "??ERROR!");
                return;
             }
     // repeat for fifty characters
   } while ((retstring[x] != 0x0D) && (x-1 != 250));
   // null terminate the return string
   retstring[x] = 0x00;
   // copy it to the string pointer
   strcpy(message, retstring);

   // and clear the receive buffers
   delay(50);
   inportb(baseAddr + RECEIVE);
   delay(50);
   inportb(baseAddr + RECEIVE);
}