Serial port Communication

Dear Experts,

i trying to read the data from serial port COM1,
though my program is correct i am not understanding how to provide the inputs and how to check its output,

Code:

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

#define PORT1 0x3F8  /* Defines Serial Port Base Address (COM1 */

void main(void){
    unsigned char c = 0;
    unsigned char chrctr = 0;
    /*int exit = 1; */

    outportb(PORT1 + 1, 0); /* Turn off interrupts */

    /* PORT1 Communication Settings */

    outportb(PORT1 + 3, 0x80); /* Set DLAB ON */
    outportb(PORT1 + 0, 0x0C); /* Set the baud rate to 9600 */

    outportb(PORT1 + 1, 0x00); /* Set Baud - Divisor latch HIGH */
    outportb(PORT1 + 3, 0x03); /* 8 bits, no parity, 1 stop */
    outportb(PORT1 + 2, 0xC7); /* FIFO Control Register */
    outportb(PORT1 + 4, 0x0B); /* Turn on DTR, RTS, and OUT2) */

    printf("Waiting on transmission from source.\nPress ESC to quit.\n");

    while(chrctr != 27){      /* Execute the loop if ESC has been hit */
    c = inportb(PORT1 + 5);
    if (c & 0x01){
        chrctr = inportb(PORT1);
        printf("%d",chrctr);
        }
    if (kbhit()){
        chrctr = getch();
        outportb(PORT1, chrctr);
        }
    }
    }"

when i execute this program at dos prompt it says

Code:

Waiting on transmission from source.\nPress ESC to quit.

and when i press escape it will come out as the loop suggest

but i want communicate through that port please tell me how to check the outputs for this program as i am not much aeware of it please experts tell me how read the data from the serial COM1.

What version of DOS is this running under?

gg

From other threads, it seems a safe bet that their real OS is something like XP, and the compiler is turboc.

I believe legacy mode of reading serial port is supported in DOS mode - of course, it assumes that COM1 is actually allocated to 0x3F8 (check in the Device Manager).

How have you set the other end up? What is sending to your serial port?


Of course for Windows XP (or any other DOS version post Windows 2.x) it will be MUCH more efficient to read and write the data through Windows (because the way that the DOS mode is handled, the data will still be sent through the Windows API, just detouring around the DOS emulations subsystem first).

--
Mats

Dear experts,

thank you for your reply,
yes i am widows xp and installed the turbo c here and trying to run that program , is it is right way,
please help me i want to communicate to serial port
COM1, what i have to do , or what modifications has to be done, in device manager which properties need to be checked,
whether it is General, Driver,Port Settings,Details or Resources.

please help me,

with regards,
vidya.

You need to check that the port-address of COM1 is 0x3F8, I think it's under resources.

You still haven't answered how you are connecting your XP system to something on the serial port.

--
Mats

Dear experts,

thank you for u r reply,
ya that COM1
i/o range it shows:03F8-03FF

what i am doing is i am working on windows Xp and installed the turbo c here,
and went through run->cmd (command line)

c:\tc>tc

i got the editor where i typed this program and compiled it compiled fine,
and when executed it simply shows nothing ,
so how to communicate properly please advice me,
how to modify this so that we can communicate please advice me.

dear Experts,

please provide me a code which does serial communication through COM ports,
really i am strucked badly ,
including please tell me how check its inputs,

please help me.

Code:

#include <stdio.h>
 
unsigned char pBuffer[1024];
 
FILE* pFile = fopen("com1:" , "r+b");
 
fread(pBuffer , 1024 , 1 , pFile);
 
fclose(pFile);

what is the output of this program,

Code:

#include <stdio.h>
 
unsigned char pBuffer[1024];
 
FILE* pFile = fopen("com1:" , "r+b");
 
fread(pBuffer , 1024 , 1 , pFile);
 
fclose(pFile);

it openes the file successfully but after nothing displays what is the output what should be checked please tell me........

Originally Posted by vin_pll

what is the output of this program,

Code:

#include <stdio.h>
 
unsigned char pBuffer[1024];
 
FILE* pFile = fopen("com1:" , "r+b");
 
fread(pBuffer , 1024 , 1 , pFile);
 
fclose(pFile);

it openes the file successfully but after nothing displays what is the output what should be checked please tell me........

Well, the above code doesn't actually output anything, so that may be why. It also expects to read 1024 bytes - which may be more than you are transmitting, so it won't actually get out of the read function itself.

You still haven't answered what you have connected to COM1 - it doesn't pick up characters out of thin air, you know....

--
Mats

dear experts,
thanks you for u r reply,
thats what i wanted at last , through COM1 iwant to connect the printer and perform some activities, like printing one of my document, how to do that how to connect the printer to that COM1 serial port,

please please tell me.

All the code you've shown so far is attempting to READ FROM the serial port. Since printers tend to "not talk a lot", you may not see much coming back FROM the serial port...

--
Mats

Before you decide that it doesn't work, I would suggest you run hyperterminal to see if there is actually anything coming in on COM1.
As matsp says, printers are not overly chatty, there may be nothing to read.

first use hyper terminal to check your com port is actually doing anything

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