serial.c

C语言库函数的源代码,是C语言学习参考的好文档。

/* +++Date last modified: 05-Jul-1997 */

/*
+----------------------------------------------------+
|               Thunderbird Software                 |
+----------------------------------------------------+
| Filespec  :  Serial.c                              |
| Date      :  October 24, 1991                      |
| Time      :  15:03                                 |
| Revision  :  1.1                                   |
|     Update: August 29, 1994                        |
+----------------------------------------------------+
| Programmer:  Scott Andrews                         |
| Address   :  5358 Summit RD SW                     |
| City/State:  Pataskala, Ohio                       |
| Zip       :  43062                                 |
+----------------------------------------------------+
| Released to the Public Domain                      |
+----------------------------------------------------+
*/

/*
+----------------------------------------------------------+
|  Call open_serial to install the interrupt handler       |
|  You must call close_serial before exiting your program  |
|  or a machine crash will occur!                          |
+----------------------------------------------------------+
*/

#include <stdlib.h>
#include <dos.h>
#include <string.h>
#include "serial.h"
#include "queue.h"

QUEUE *Serial_In_Queue;
QUEUE *Serial_Out_Queue;

OLD_COMM_PARAMS old_comm_params;
COMM_STATUS     comm_status;

void (INTERRUPT FAR *oldvector_serial )(); 
/* save addr for intr handler */

int  ComBase;                        /* Comm port address */
int  IrqNum;                         /* Comm interrupt request */

int OpenComPort ( char Port )        /* install int. handler */
{
      unsigned status;
      int retval = -1;
    
      /* allocate input and output queues */

      Serial_In_Queue = alloc_queue( SerInBufSize );
      if ( (QUEUE *) 0 == Serial_In_Queue)
            return retval;
      Serial_Out_Queue = alloc_queue( SerOutBufSize );
      if ( (QUEUE *) 0 == Serial_Out_Queue)
      {
            free ( Serial_In_Queue );
            return retval;
      }
      retval = 0;

      /* Setup Comm base port address and IRQ number */

      switch ( Port)
      {
            case '1': ComBase = 0x3F8; IrqNum = 4; break;
            case '2': ComBase = 0x2F8; IrqNum = 3; break;
            case '3': ComBase = 0x3E8; IrqNum = 4; break;
            case '4': ComBase = 0x2E8; IrqNum = 3; break;
            default : ComBase = 0x3F8; IrqNum = 4; break;
      }
      old_comm_params.int_enable = inp ( ComBase + INT_EN );
      outp ( ComBase + INT_EN, 0 ); /* turn off comm interrupts */

      /* save old comm parameters */

      old_comm_params.line = inp ( ComBase + LINE_CNTRL );
      old_comm_params.modem = inp ( ComBase + MODEM_CNTRL );
      status = inp ( ComBase + LINE_CNTRL );
      outp ( ComBase + LINE_CNTRL, (unsigned char) status | 0x80 );
      old_comm_params.baud_lsb = inp ( ComBase + BAUD_LSB );
      old_comm_params.baud_msb = inp ( ComBase + BAUD_MSB );
      status = inp ( ComBase + LINE_CNTRL );
      outp ( ComBase + LINE_CNTRL, (unsigned char) status | 0x7F );
      status = OUT2 | DTR;              /* DTR/OUT2 must be set! */
      outp ( ComBase + MODEM_CNTRL, (unsigned char) status );

      /* get serial port address/vector */

      oldvector_serial = (void(INTERRUPT FAR *)(void))getvect(IrqNum + 8 );

      /* set our interrupt handler */

      setvect ( IrqNum + 8, serial );

      /* save the PIC */

      old_comm_params.int_cntrl = inp ( 0x21 );
      status = ( 1 << IrqNum);      /* calculate int enable bit */
      status = ~status;

      /* ok enable comm ints */

      outp ( 0x21, (unsigned char) old_comm_params.int_cntrl & 
            (unsigned char) status );
      return retval;
}

void CloseComPort ( void )
{
      int status;

      /* restore UART to previous state */

      outp ( ComBase + INT_EN, (unsigned char) 0 );
      outp ( ComBase + MODEM_CNTRL, 
            (unsigned char) old_comm_params.modem );
      status = inp ( ComBase + LINE_CNTRL );
      outp ( ComBase + LINE_CNTRL, 
            (unsigned char) status | 0x80 );
      outp ( ComBase + BAUD_LSB, 
            (unsigned char) old_comm_params.baud_lsb );
      outp ( ComBase + BAUD_MSB, 
            (unsigned char) old_comm_params.baud_msb );
      outp ( ComBase + LINE_CNTRL, 
            (unsigned char) old_comm_params.line );
      outp ( 0x21, (unsigned char) old_comm_params.int_cntrl );

      /* restore old interrupt handler */

      setvect ( IrqNum + 8, oldvector_serial );

      /* free input and output queues */

      free ( Serial_In_Queue );
      free ( Serial_Out_Queue );
      return;
}

void InitComPort ( char Baud[], char Databits, 
                   char Parity, char Stopbits )
{
      int status;
      long baudrate;
      unsigned divisor;

      /* set baud rate */

      status = inp ( ComBase + LINE_CNTRL );
      outp ( ComBase + LINE_CNTRL, 
            (unsigned char) status | 0x80 );
      baudrate = atol ( Baud );
      if ( baudrate == 0)
            baudrate = 2400L;
      divisor = (unsigned) ( 115200L / baudrate);
      outp ( ComBase + BAUD_LSB, 
            (unsigned char) ( divisor & 0x00FF) );
      outp ( ComBase + BAUD_MSB, 
            (unsigned char) ( ( divisor >> 8) & 0x00FF) );
      status = 0x00;

      /* set parity */

      switch ( Parity)                    /* set parity value     */
      {
      case 'O':                           /* odd parity           */
      case 'o':
            status = 0x08; break;

      case 'E':                           /* even parity          */
      case 'e':
            status = 0x18; break;

      case 'S':                           /* stick parity         */
      case 's':
            status = 0x28; break;

      case 'N':                           /* no parity            */
      case 'n':
            default :   status = 0x00;
      }

    /* set number data bits */

      switch ( Databits)
      {
      case '5':
            break;

      case '6':
            status = status | 0x01;
            break;

      case '7':
            status = status | 0x02;
            break;

      case '8':
      default :
            status = status | 0x03;
      }

      /* set number stop bits */

      switch ( Stopbits)
      {
      case '2':
            status = status | 0x04;
            break;

      case '1':
      default :
            ;
      }
      outp ( ComBase + LINE_CNTRL, (unsigned char) status );
      status = OUT2 | DTR;        /* DTR/OUT2 must be set! */
      outp ( ComBase + MODEM_CNTRL, (unsigned char) status );

      /* enable serial interrupts */

      outp ( ComBase + INT_EN, RX_INT | ERR_INT | RS_INT );
      return;
}

void DropDtr ( void )
{
      int status;

      status = inp ( ComBase + MODEM_CNTRL );
      status &= 0xFE;                 /* turn off DTR bit */
      outp ( ComBase + MODEM_CNTRL, (unsigned char) status );
      return;
}

void RaiseDtr ( void )
{
      int status;

      status = inp ( ComBase + MODEM_CNTRL );
      status |= 0x01;                  /* turn on DTR bit */
      outp ( ComBase + MODEM_CNTRL, (unsigned char) status );
      return;
}

int ComRecChar ( void )
{
      return de_queue ( Serial_In_Queue );
}

int ComSendString ( char *string )
{
      int retval;
      char *pointer;
      pointer = string;

      while ( *pointer)
      {
            retval = en_queue ( Serial_Out_Queue, *pointer );
            pointer++;
      }
      if ( 0x0 == (comm_status.modem & 0x40))
            RaiseDtr ();
      outp ( ComBase + INT_EN, RX_INT | TBE_INT | ERR_INT | RS_INT );
      return retval;
}

int ComSendChar ( char character )
{
      int retval;

      /* interrupt driven send */

      if ( 0x0 == (comm_status.modem & 0x40))
            RaiseDtr ();
      retval = en_queue ( Serial_Out_Queue, character );
      if ( - 1 != retval)
            outp ( ComBase + INT_EN, RX_INT | TBE_INT | ERR_INT | RS_INT );
      return retval;
}

int ComStatus ( void )
{
      unsigned status;
      unsigned retval;

      retval = inp ( ComBase + LINE_STATUS );
      retval = retval << 8;
      status = inp ( ComBase + MODEM_STATUS );
      retval = retval | status;
      if ( queue_empty ( Serial_In_Queue ))
            retval &= 0xFEFF;
      else  retval |= 0x0100;
      return (int) retval;
}

void INTERRUPT FAR serial ( void )            /* interrupt handler */
{
      int temp;

      disable ();
      while ( 1)
      {
            comm_status.intrupt = inp ( ComBase + INT_ID );
            comm_status.intrupt &= 0x0f;
            switch ( comm_status.intrupt)
            {
            case 0x00:                 /* modem interrupt */
                  comm_status.modem = inp( ComBase + MODEM_STATUS );
                  break;

            case 0x02:                 /* xmit interrupt */
                  if ( queue_empty ( Serial_Out_Queue ))
                        outp(ComBase + INT_EN, RX_INT|ERR_INT|RS_INT );
                  else
                  {
                        temp = de_queue ( Serial_Out_Queue );
                        if ( - 1 != temp)
                              outp ( ComBase + XMIT, temp );
                  }
                  break;

            case 0x04:                 /* receive interrupt */
                  en_queue(Serial_In_Queue, (char)inp(ComBase + REC));
                  break;

            case 0x06:                 /* line interrupt */
                  comm_status.line = inp ( ComBase + LINE_STATUS );
                  (void) inp ( ComBase + REC );
                  en_queue ( Serial_In_Queue, '!' );
                  break;

            default:                   /* No Mo` Left */
                  comm_status.modem = inp ( ComBase + MODEM_STATUS );
                  outp ( 0x20, 0x20 );
                  enable ();
                  return;
            }   /* switch */
      }   /* while */
}
/* End of Serial.C */