Thread: C and Arduino

Hi there,

I want to send 3 commands via serial (USB) to an Arduino based device. The thing that i want to do is this: I have a program in C that reads a txt file. In that file I write 3 values: 1, 2, 3. I write one value than I delete it and write another.
My C program should read those values and send a command to Arduino via Serial USB. This command should light a LED.

Something like this: if I write 1 in the txt file the Arduino will light the first LED, write 2-> second LED will be ON, and so..

My question is: what should I add to my C program so the program could send this kind of commands?

Right!

I use windows XP and 7 with visual studio 2010.

I can't just send the command from the C program?

This is not what I need

I can't just send the command from the C program?

Yes, once you properly establish communications with your device, which is the purpose of the above link.

This is not what I need

Then show us exactly what you need. Post the code showing what you've tried.

Jim

Ok, I understand. I am going to post the code soon.

You will need to open the serial/USB port, configure the post, and write characters to that port, it is not as simple as opening a file. Although it is the same principle. The link you were given is the starting point, the documentation for the call needed to open your port for communication.

Here is one example of doing basically what your trying to do. Serial Send.

There are also several books dealing with this issue. Here is one example: The Windows Serial Port Handbook

And in case you want a Windows or Linux example.,

And don't forget this is only half the battle. You'll still need to properly setup your Arduino to properly communicate with your program.


Jim

I have made some 'research' and I read the CreateFile function (Windows) and I also find Serial Communication in Windows

I have a question: everywhere it says that I have to open my COM port.

Code:

HANDLE m_hCommPort = ::CreateFile( szPortName,
       GENERIC_READ|GENERIC_WRITE,  // access ( read and write)
       0,                           // (share) 0:cannot share the
                                    // COM port
       0,                           // security  (None)
       OPEN_EXISTING,               // creation : open_existing
       FILE_FLAG_OVERLAPPED,        // we want overlapped operation
       0                            // no templates file for
                                    // COM port...
       );

This is an example of how I can open the COM port. My question: I have to write this code in cmd? I have no idea of how I can do this, maybe it sounds stupid...

Depending on your circumstances you may wish to look into libusb (see windows_backend for example).

That way you have the advantage that your application will be cross-platform (for the most part) and if/when you switch to Linux or OSX (for example) making your code work should be relatively trivial.