Serial Communication [RS232]

**johnny_hush** · 01-15-2008

Hi everyone!

I need to create a program to receive and send some data using RS232.
Program should receive 16 bytes of data, sore it and than I'll write switch case, so if some specific data is received, program will go to specific label.

In C I know a lot of basic things, but I'm asking you to help me with this.

The program is supposed to run in Windows XP. The most helpful thing would be if someone could post some example code (with comments), where the data is being received [16bytes] and sored.

Anyone, who can help me is welcome!

Johnny

**invinciblevn** · 01-15-2008

Originally Posted by johnny_hush

Hi everyone!

I need to create a program to receive and send some data using RS232.
Program should receive 16 bytes of data, sore it and than I'll write switch case, so if some specific data is received, program will go to specific label.

In C I know a lot of basic things, but I'm asking you to help me with this.

The program is supposed to run in Windows XP. The most helpful thing would be if someone could post some example code (with comments), where the data is being received [16bytes] and sored.

Anyone, who can help me is welcome!

Johnny

As I remember, it is not easy to touch to low level of hardware in XP with pure C.
It is protected.
With pure C you should work on DOS or Win98, it's better.
In XP, you can use VC++ which has a class for COM object, you simply config port as you need and use it very easily. Details you can find in MSDN.

**robwhit** · 01-15-2008

I think you can just open up COM1 with fopen or something.

like fopen("COM1", "rb"); or something.

**novacain** · 01-15-2008

Use CreateFile() to open the com port (check returns for error)
sprintf(temp,"\\\\.\\COM%d",iComPort);//name of port to open in CreateFile()

Get the port settings with GetCommState()
Modify and set with SetCommState()

Get the timeouts with GetCommTimeouts() [controls how long to wait for data]
Modify and set with SetCommTimeouts()

Read the data with ReadFile(). Check both the return and compare the amount of data requested with the amount actually read.

Store in buffer.....

**johnny_hush** · 01-15-2008

Do you perhaps have some little tutorial or document?

**johnny_hush** · 01-15-2008

Thanks invinciblevn!

Can I write program for Win98 and turn on Compatibility Mode in program properties (run in Windows 98 mode)?

Will this solve problem?

And how to 'communicate' even in win98, give some code, explanations, please...

johnny

**invinciblevn** · 01-15-2008

Originally Posted by johnny_hush

Thanks invinciblevn!

Can I write program for Win98 and turn on Compatibility Mode in program properties (run in Windows 98 mode)?

Will this solve problem?

And how to 'communicate' even in win98, give some code, explanations, please...

johnny

You have to use interrupt 14 for interfacing.
I worked with this quite long time along, so that i can not remember detail. Sorry.
If you can use Visual C++ or Visual Basic, it's quite easy.
They support every thing, if you can please use them. And I can send you some example codes.

**Adak** · 01-15-2008

You can't write com code without knowing all the details you left out:

The baud rate, protocol, etc., of the external device!

Your external device should have some resources for getting this done - usually they include their own com program you can tailor to fit your needs.

Lacking that, I'd check out the open source code/programming projects forums, and see what you can find that might be suitable. Don't forget the newsgroups archives, as well, and GIYF, for sure. There is a wealth of info on RS232 also, on the net.

What will work in your com program, depends on what your device has in hardware and it's own software.

**robwhit** · 01-15-2008

http://forums.devshed.com/c-programm...2t-162565.html
http://msdn2.microsoft.com/en-us/library/ms810467.aspx

**novacain** · 01-15-2008

Ummmm....no.

I code this type of thing a lot and so know it fairly well.

Have a try, then post your code (and what goes wrong or you can not work out) and I am sure someone will help fix it.

A lot of it depends on the implementation (ie timeouts, port settings change depending on the device you are communicating with etc).

Good Luck!

**Codeplug** · 01-15-2008

http://msdn2.microsoft.com/en-us/library/ms810467.aspx

http://cboard.cprogramming.com/showthread.php?t=47870

gg

**Salem** · 01-16-2008

Threads merged.

**matsp** · 01-16-2008

First of all, I doubt there's a way around the WinXP protection, second, why would you want to make things awkward for yourself, when there is a nice, portable, flexible and complete interface in XP? [That works with Win98 too, should you wish to "go backwards" - which certainly isn't true for the other way around].

Reading/writing the serial port directly is far from trivial, and if you don't have access to the interrupt handler [which you absolutely haven't] you'll not be able to figure out when data is available on the serial port, or when you can send the next byte out. So you'd end up polling the port, which means that you'd spend ALL of the system CPU time on polling, which isn't the right thing to do.

--
Mats

Thread: Serial Communication [RS232]

Thread Tools

Search Thread

Display

Serial Communication [RS232]

Similar Threads

Duplex communication thro serial port

Serial port Communication

Serial pot communication through c program

Please help with serial communication problem - Long

Serial communication packets