Problem with real-time app reading from serial port
 

Hello,
I'm facing a with a real-time app. This real-time app is reading data from the serial port, then, process it. However, it seems to miss some data when the computer has some other apps running. More data are lost when other app do heavier processing. When i try to search for files in the computer and at the same time running the real-time app, it seems to miss more than half of the data sent. How can i overcome this problem? Is it hardware or the program's problem?

Thank you!!! ;)