hi to all,

can anyone help me writing a program that can set a pin of the serial com1 port at 12v+?

it must be simple command line based,for example, program.exe -on or -off.

any pin will work.

thanks in advance :)

You just cannot control the port so precisely that you can switch a pin on or off as you like.
If you want to use your computer as a switch, you should had some additional electronics behind
the port.
The problem is that any information sent to the port appears during a short period of time.

This windows program just switches the TX pin of the port during a short period
(enough to be detected by a circuit anyway).

#include <windows.h>
#include <iostream>
#include <string>
using namespace std;

void set_com_pin(bool value);

int main(int argc, char *argv)
{
	if(argc != 2)
	{
		cerr<<"bad usage !"<endl;
		return -1;
	}
	
	bool onoff;
	if(string(argv[1])==string("-on"))onoff=true;
	else if(string(argv[1])==string("-off"))onoff=false;
	else 
	{
		cerr<<"bad parameters !"<<endl;
		return -1;
	}
	
	set_com_pin(onoff);
	return 0;	
}

void set_com_pin(bool value)
{
	HANDLE hPort=CreateFile("COM1", GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL);
	if(hPort==INVALID_HANDLE_VALUE)
	{
		cerr<<"there is a problem"<<endl;
		return;
	}
	DCB dcb;
	GetCommState(hPort, &dcb);
	dcb.BaudRate=CBR_110; //we slow down the port
	SetCommState(hPort, &dcb);

	//we send the data;

	char data=value?0xFF:0x00;
	DWORD written=0;
	WriteFile(hPort, &data, 1, &written, NULL);
	CloseHandle(hPort);
	if(written!=1)
	{
		cerr<<"there is a problem"<<endl;
	}
}

another solution could be the use of two programs : a daemon, in a separate process, that repeatedely writes on the serial port, an a controller, that would
communicate with the daemon to turn it on/off (your program.exe), using named mutexes.

If I have some more time...

hi crazydieter,
thanks for your code!
well, actually just having the 12v+ signal for a moment can be enough for what im doing,as you guessed im triggering a pic to start a routine and the pic is controlling some pins in the lpt port.

i just tried to compile your code, but, i have almost 0 knowledge about coding and programming.

i have 2 compilers in this machine ,djgpp and mingw.

can you tell me what commands to use for compiling the code?

thanks again :)

No problem !

In fact, there were some errors in my code (i haven't tried to compile and test it yet).

Here is a corrected working version :

#include <windows.h>
#include <iostream>
#include <string>
using namespace std;

void set_com_pin(bool value);

int main(int argc, char **argv)
{
	if(argc != 2)
	{
		cerr<<"bad usage !"<<endl;
		return -1;
	}

	bool onoff;
	if(string(argv[1])==string("-on"))onoff=true;
	else if(string(argv[1])==string("-off"))onoff=false;
	else
	{
		cerr<<"bad parameters !"<<endl;
		return -1;
	}

	set_com_pin(onoff);
	return 0;
}

void set_com_pin(bool value)
{
	HANDLE hPort=CreateFile("COM1", GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
	if(hPort==INVALID_HANDLE_VALUE)
	{
		cerr<<"there is a problem"<<endl;
		return;
	}
	DCB dcb;
	GetCommState(hPort, &dcb);
	dcb.BaudRate=CBR_110; //we slow down the port
	SetCommState(hPort, &dcb);

	//we send the data;

	char data=value?0x00:0xFF;//in fact, for serial ports, logical zero corresponds to +12v (!)
	DWORD written=0;
	WriteFile(hPort, &data, 1, &written, NULL);
	CloseHandle(hPort);
	if(written!=1)
	{
		cerr<<"there is a problem"<<endl;
	}
}

As it uses windows-specific libraries, you have to use mingw to compile it.

personally, I use dev-cpp.

try :
g++.exe com.cpp -o com.exe. If you have errors, send me a private message with an email adress so i can send you the compiled program.

Dieter

hi crazydieter,

i had a problem compiling the code again:

C:/MINGW/BIN/../lib/gcc-lib/mingw32/3.2.2/../../../libstdc++.a(c++locale.o)(.tex
t+0x3a0): undefined reference to `strtold'

can you please mail me the binary?

jesusdlvr@hotmail.com

thanks!

hi crazydieter,

i had a problem compiling the code again:

C:/MINGW/BIN/../lib/gcc-lib/mingw32/3.2.2/../../../libstdc++.a(c++locale.o)(.tex
t+0x3a0): undefined reference to `strtold'

Maybe use strtod instead of strtold and be sure to #include <cstdlib>.

can you please mail me the binary?

<< moderator edit: removed email address >>

thanks!

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Hi i need to switch on & switch off my device using dtr pin in db9. i am using max232 ic.
hardware side evrything is fine but i need software coding to control dtr in db-9(-12V TO +12V). iam trying to do in C or C++. CAN YOU HELP ME IN THIS PROJECT ASAP.

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