Error while connecting to realtime target

Hi, I made level 2 s-function in C language, which sends some data via serial port. I compiled it with Microsoft Visual C++ 2008 SP1 compiler. When I add this s-function to simulink model and start the simulation in normal mode, everything is ok, but, when I want to connect with realtime target (after building with rtwin.tlc), I get this error message:

Error occurred while executing External Mode MEX-file 'rtwinext': Error loading real-time executable: undefined symbol "_InterlockedExchangeAdd"

I have not any idea, what this error means. Could anybody help me? Thanks.

[Kaustubha Govind]

Do you think the failure is specific to your S-function, or do you see it even without your S-function. For example, you could try the example model 'rtvdp' and see if you can execute that in external mode successfully.

[Miroslav]

Yes I can use external mode. I supose thet problem is with using windows.h in my s-function. Simulink can't use windows API function in external mode.

Answer 1

[Jan Houska]

For serial port communication, please use Packet Output or Stream Output blocks, depending on your data format. You are correct that you cannot use Windows API in real-time code.

[Miroslav]

I know Stream and packet input block, but i need read data from input buffer asynchronous. I need execute some functions after every single byte is received. I supposed that s-function could help me. I could to use Stream input block placed in function call subsystem, which is call with hardware interrupt (byte receive). I have not any idea how hardware interrupt work in simulink external mode. Is it possible?

Answer 2

[Jan Houska]

If you want to react to individual received bytes, it is probably best to sample (poll) the input fast enough. I'd recommend the Packet Input block with a sample rate of, say, 0.5ms, and using its Data Ready output to trigger any necessary action.