/* DOS program to set the digital output port.

   Syntax:     DOUT</port> HEX_BYTE

   </port>     Optional LPT port number - defaults to LPT1
   HEX_BYTE    8-bit hex value to write to output port

   On exit:    ERRORLEVEL = 0 if all OK
               ERRORLEVEL = 1 if parameter error or invalid LPT port
*/


#include <stdio.h>
#include <stdlib.h>
#include <dos.h>

#define LPT1   0x00400008  /* BIOS printer address entries */
#define LPT2   0x0040000a
#define LPT3   0x0040000c
#define LPT4   0x0040000e

#define STROBE 0x01        /* Strobe bit for digital output port */



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


int main(int argc, char *argv[])
  {
    unsigned int port,                  /* LPT port address             */
                 data;                  /* Hex output data              */
    unsigned int far *bios_printer_addr;
    char status;                        /* Holds status of control port */
    int lpt_number;                     /* Holds LPT port number passed
                                           via command line             */


    switch(argc)
      {
        case 1:
               printf("Set the digital output port to the specified hex value.\n\n");
               printf("DOUT</port> HEX_BYTE\n\n");
               printf("</port>     Optional LPT port number - defaults to LPT1.\n");
               printf("HEX_BYTE    8-bit hex value to write to output port.\n\n");
               printf("On exit, ERRORLEVEL = 1 if parameter error.\n");
               exit(1);

        case 2:
               if (argv[1][0]=='/')
                 {
                   puts("Missing output data");
                   exit(1);
                 }

               port=*(bios_printer_addr=LPT1);
               if (port==NULL)
                 {
                   puts("LPT1 does not exist");
                   exit(1);
                 }
               sscanf(argv[1],"%x",&data);
               break;

        case 3:
	             if (argv[1][0]=='/') lpt_number=atoi(argv[1]+1);

	             switch(lpt_number)
	               {
	                 case 1 :
	                          port=*(bios_printer_addr=LPT1);
                            if (port==NULL)
                              {
                                puts("LPT1 does not exist");
                                exit(1);
                              }
                            sscanf(argv[2],"%x",&data);
	                          break;

	                 case 2 :
	                          port=*(bios_printer_addr=LPT2);
                            if (port==NULL)
                              {
                                puts("LPT2 does not exist");
                                exit(1);
                              }
                            sscanf(argv[2],"%x",&data);
	                          break;

                   case 3 :
                            port=*(bios_printer_addr=LPT3);
                            if (port==NULL)
                              {
                                puts("LPT3 does not exist");
                                exit(1);
                              }
                            sscanf(argv[2],"%x",&data);
                            break;

                   case 4 :
                            port=*(bios_printer_addr=LPT4);
                            if (port==NULL)
                              {
                                puts("LPT4 does not exist");
                                exit(1);
                              }
                            sscanf(argv[2],"%x",&data);
                            break;

	                 default:
                            puts("Invalid printer port");
	                          exit(1);
	               }
      }

    status=inportb(port+2);            /* Save control port status */
    outportb(port,(char)data);         /* Set up data              */
    delay(1);
    outportb(port+2,status&~STROBE);   /* Strobe high              */
    delay(1);
    outportb(port+2,status|STROBE);    /* Strobe low               */
    delay(1);
    outportb(port+2,status&~STROBE);   /* Strobe high              */

    return 0;
  }