DOS, Serial, and Touch Screen

Hi Everyone,

I have a question. I've been working on a program in DOS for a small touchscreen computer that goes in my house. The touchscreen input on internally attached to COM3 (0x2E8h I think is the base address) using interrupt 15.

I've worked with programming the serial port before, but only on ports 1 & 2. I found some C code that I used before (found it on the internet a while ago) and modified it so that it can use COM3. Now, I'm not quite sure if something needs to be changed because it is on a different interrupt (I think COM3 is normally on IRQ4?)... but that's where I am confused. Its very messy code, I'm just trying to get some input from the controller. Can anyone help me out, maybe point out things that need to be changed? It initializes fine, but I don't receive any input from the controller. Anyway, any help would be appreciated!

Code:

---

/*---------------------------------------------------------------------*
  FILENAME:                    SERIAL.H

                  Some definitions used by SERIAL.C

 *--------------------------------------------------------------------*/

/* Defines Serial Ports Base Address ADDED BY ME*/
/* COM1 0x3F8                        */
/* COM2 0x2F8                              */
/* COM3 0x3E8                              */
/* COM4 0x2E8                              */


#define COM1            1
#define COM2            2
#define COM1BASE        0x3F8  /*  Base port address for COM1  */
#define COM2BASE        0x2F8  /*  Base port address for COM2  */

/*
    The 8250 UART has 10 registers accessible through 7 port addresses.
    Here are their addresses relative to COM1BASE and COM2BASE. Note
    that the baud rate registers, (DLL) and (DLH) are active only when
    the Divisor-Latch Access-Bit (DLAB) is on. The (DLAB) is bit 7 of
    the (LCR).

        o TXR Output data to the serial port.
        o RXR Input data from the serial port.
        o LCR Initialize the serial port.
        o IER Controls interrupt generation.
        o IIR Identifies interrupts.
        o MCR Send contorl signals to the modem.
        o LSR Monitor the status of the serial port.
        o MSR Receive status of the modem.
        o DLL Low byte of baud rate divisor.
        o DHH High byte of baud rate divisor.
*/
#define TXR            0      /*  Transmit register (WRITE) */
#define RXR            0      /*  Receive register  (READ)  */
#define IER            1      /*  Interrupt Enable          */
#define IIR            2      /*  Interrupt ID              */
#define LCR            3      /*  Line control              */
#define MCR            4      /*  Modem control            */
#define LSR            5      /*  Line Status              */
#define MSR            6      /*  Modem Status              */
#define DLL            0      /*  Divisor Latch Low        */
#define DLH            1      /*  Divisor latch High        */


/*-------------------------------------------------------------------*
  Bit values held in the Line Control Register (LCR).
        bit                meaning
        ---                -------
        0-1                00=5 bits, 01=6 bits, 10=7 bits, 11=8 bits.
        2                Stop bits.
        3                0=parity off, 1=parity on.
        4                0=parity odd, 1=parity even.
        5                Sticky parity.
        6                Set break.
        7                Toggle port addresses.
 *-------------------------------------------------------------------*/
#define NO_PARITY      0x00
#define EVEN_PARITY    0x18
#define ODD_PARITY      0x08



/*-------------------------------------------------------------------*
  Bit values held in the Line Status Register (LSR).
        bit                meaning
        ---                -------
        0                Data ready.
        1                Overrun error - Data register overwritten.
        2                Parity error - bad transmission.
        3                Framing error - No stop bit was found.
        4                Break detect - End to transmission requested.
        5                Transmitter holding register is empty.
        6                Transmitter shift register is empty.
        7              Time out - off line.
 *-------------------------------------------------------------------*/
#define RCVRDY          0x01
#define OVRERR          0x02
#define PRTYERR        0x04
#define FRMERR          0x08
#define BRKERR          0x10
#define XMTRDY          0x20
#define XMTRSR          0x40
#define TIMEOUT                0x80

/*-------------------------------------------------------------------*
  Bit values held in the Modem Output Control Register (MCR).
        bit            meaning
        ---                -------
        0                Data Terminal Ready. Computer ready to go.
        1                Request To Send. Computer wants to send data.
        2                auxillary output #1.
        3                auxillary output #2.(Note: This bit must be
                        set to allow the communications card to send
                        interrupts to the system)
        4                UART ouput looped back as input.
        5-7                not used.
 *------------------------------------------------------------------*/
#define DTR            0x01
#define RTS            0x02
#define MC_INT                0x08


/*------------------------------------------------------------------*
  Bit values held in the Modem Input Status Register (MSR).
        bit                meaning
        ---                -------
        0                delta Clear To Send.
        1                delta Data Set Ready.
        2                delta Ring Indicator.
        3                delta Data Carrier Detect.
        4                Clear To Send.
        5                Data Set Ready.
        6                Ring Indicator.
        7                Data Carrier Detect.
 *------------------------------------------------------------------*/
#define CTS            0x10
#define DSR            0x20


/*------------------------------------------------------------------*
  Bit values held in the Interrupt Enable Register (IER).
        bit                meaning
        ---                -------
        0                Interrupt when data received.
        1                Interrupt when transmitter holding reg. empty.
        2                Interrupt when data reception error.
        3                Interrupt when change in modem status register.
        4-7                Not used.
 *------------------------------------------------------------------*/
#define RX_INT          0x01


/*------------------------------------------------------------------*
  Bit values held in the Interrupt Identification Register (IIR).
        bit                meaning
        ---                -------
        0                Interrupt pending
        1-2            Interrupt ID code
                        00=Change in modem status register,
                        01=Transmitter holding register empty,
                        10=Data received,
                        11=reception error, or break encountered.
        3-7                Not used.
 *------------------------------------------------------------------*/
#define RX_ID          0x04
#define RX_MASK        0x07


/*
    These are the port addresses of the 8259 Programmable Interrupt
    Controller (PIC).
*/
#define IMR            0x21  /* Interrupt Mask Register port */
#define ICR            0x20  /* Interrupt Control Port      */


/*
    An end of interrupt needs to be sent to the Control Port of
    the 8259 when a hardware interrupt ends.
*/
#define EOI            0x20  /* End Of Interrupt */


/*
    The (IMR) tells the (PIC) to service an interrupt only if it
    is not masked (FALSE).
*/
#define IRQ3            0xF7  /* COM2 */
#define IRQ4            0xEF  /* COM1 */

//
// #defines removed from serial.c - 18 Aug 1991
//
#define VERSION 0x0101

#define SFALSE          0
#define STRUE          (!FALSE)

#define NOERROR        0      /* No error              */
#define BUFOVFL        1      /* Buffer overflowed      */

#define ESC            0x1B    /* ASCII Escape character */
#define ASCII          0x007F  /* Mask ASCII characters  */
#define SBUFSIZ        0x4000  /* Serial buffer size    */

---

Now, for the main program....

I commented a lot of the parts out that I didn't think were needed

Code:

---

//                * Compile this program with Test Stack Overflow OFF.
//  *------------------------------------------------------------------*/
#include <dos.h>
#include <conio.h>
#include <stdio.h>
#include <string.h>
#include "serial2.h"
int            SError          = NOERROR;
int            portbase        = 0x2E8;
void          interrupt(*oldvects[2])();

static  char  ccbuf[SBUFSIZ];
unsigned int  startbuf        = 0;
unsigned int  endbuf          = 0;


/* Handle communications interrupts and put them in ccbuf */
void  interrupt com_int(void)
{
//snap_rx        *net_rx;
        disable();
        if ((inportb(portbase + IIR) & RX_MASK) == RX_ID)
        {
                  if (((endbuf + 1) & SBUFSIZ - 1) == startbuf)
                                SError = BUFOVFL;

                  ccbuf[endbuf++] = inportb(portbase + RXR);

                  endbuf &= SBUFSIZ - 1;
        }

        /* Signal end of hardware interrupt */
        outportb(ICR, EOI);
        enable();
}

/* Output a character to the serial port */
int    serialOut(char x)
{
        long int          timeout = 0x0000FFFFL;

        outportb(portbase + MCR,  MC_INT | DTR | RTS);

        /* Wait for Clear To Send from modem */
        while ((inportb(portbase + MSR) & CTS) == 0)
                  if (!(--timeout))
                                return (-1);

        timeout = 0x0000FFFFL;

        /* Wait for transmitter to clear */
        while ((inportb(portbase + LSR) & XMTRDY) == 0)
                  if (!(--timeout))
                                return (-1);

        disable();
        outportb(portbase + TXR, x);
        enable();

        return (0);
}

/* Output a string to the serial port */
void  serialString(char *string)
{
        while (*string)
                serialOut(*string++);
}

/* This routine returns the current value in the buffer */
int    getccb(void)
{
        int                res;

        if (endbuf == startbuf)
                  return (-1);

        res = (int) ccbuf[startbuf++];
        startbuf %= SBUFSIZ;
        return (res);
}

/* Install our functions to handle communications */
void  setvects(void)
{
        oldvects[0] = getvect(0x0B);
        oldvects[1] = getvect(0x0C);
        setvect(0x0B, com_int);
        setvect(0x0C, com_int);
}

/* Uninstall our vectors before exiting the program */
void  resvects(void)
{
        setvect(0x0B, oldvects[0]);
        setvect(0x0C, oldvects[1]);
}

/* Turn on communications interrupts */
void  i_enable(int pnum)
{
        int                c;

        disable();
        c = inportb(portbase + MCR) | MC_INT;
        outportb(portbase + MCR, c);
        outportb(portbase + IER, RX_INT);
        c = inportb(IMR) & (0xEF);
        outportb(IMR, c);
        enable();
}

/* Turn off communications interrupts */
void  i_disable(void)
{
        int                c;

        disable();
        c = inportb(IMR) | ~IRQ3 | ~IRQ4;
        outportb(IMR, c);
        outportb(portbase + IER, 0);
        c = inportb(portbase + MCR) & ~MC_INT;
        outportb(portbase + MCR, c);
        enable();
}

/* Tell modem that we're ready to go */
void  comm_on(void)
{
        int                c, pnum;

//        pnum = (portbase == COM1BASE ? COM1 : COM2);
//        i_enable(3);
        c = inportb(portbase + MCR) | DTR | RTS;
        outportb(portbase + MCR, c);
}

/* Go off-line */
void  comm_off(void)
{
        i_disable();
        outportb(portbase + MCR, 0);
}

void  initSerial(void)
{
        endbuf = startbuf = 0;
        setvects();
        comm_on();
}

void  closeSerial(void)
{
        comm_off();
        resvects();
}

/* Set the port number to use */
int    setPort(int port)
{
        int                offset, far *RS232_Addr;

//        switch (port)
//        { /* Sort out the base address */
//                case COM1 : offset = 0x0000;
//                                                break;
//                case COM2 : offset = 0x0002;
//                                                break;
//                default  : return (-1);
//        }

//        RS232_Addr = MK_FP(0x0040, offset);  /* Find out where the port is. */
//        if (*RS232_Addr == NULL) return (-1);/* If NULL then port not used. */
//        portbase = *RS232_Addr;              /* Otherwise set portbase      */

        return (0);
}

/* This routine sets the speed; will accept funny baud rates. */
/* Setting the speed requires that the DLAB be set on.        */
int    setSpeed(int speed)
{
        char                c;
        int                divisor;

        if (speed == 0)            /* Avoid divide by zero */
                  return (-1);
        else
                  divisor = (int) (115200L/speed);

        if (portbase == 0)
                  return (-1);

        disable();
        c = inportb(portbase + LCR);
        outportb(portbase + LCR, (c | 0x80)); /* Set DLAB */
        outportb(portbase + DLL, (divisor & 0x00FF));
        outportb(portbase + DLH, ((divisor >> 8) & 0x00FF));
        outportb(portbase + LCR, c);          /* Reset DLAB */
        enable();

        return (0);
}

/* Set other communications parameters */
int    setOthers(int parity, int bits, int stopBit)
{
        int                setting;

        if (portbase == 0)                                        return (-1);
        if (bits < 5 || bits > 8)                          return (-1);
        if (stopBit != 1 && stopBit != 2)                  return (-1);
        if (parity != NO_PARITY && parity != ODD_PARITY && parity != EVEN_PARITY)
                                                        return (-1);

        setting  = bits-5;
        setting |= ((stopBit == 1) ? 0x00 : 0x04);
        setting |= parity;

        disable();
        outportb(portbase + LCR, setting);
        enable();

        return (0);
}

/* Set up the port */
int    setSerial(int port, int speed, int parity, int bits, int stopBit)
{
        if (setPort(port))                    return (-1);
        if (setSpeed(speed))                  return (-1);
        if (setOthers(parity, bits, stopBit)) return (-1);

        return (0);
}

---

Thanks everyone!

Jon scott