Abstract

The programming of real-time applications nowadays involves multitasking using timing demands with microsecond resolution, inter task messaging including semaphores for synchronization of multiple running tasks. For solving this task efficiently a programmer likes to use graphical visualization methods for program flow, messaging and priority dependencies. Instead of using graphical methods only for debugging and schematic overviews of analysis problems typical for real-time and multitasking, the graphical programming environment LabVIEW(tm) by National Instruments provides state-of-the-art tools for solving programming tasks by just doing graphical formulation of algorithms and data flow. One major disadvantage of LabVIEW, not being able to be used as programming environment for hard real-time in kernel space, could be eliminated using the user space API 'LXRT' of the RTAI 'Real Time Application Interface' for Linux. It is shown, that by implementing a generalized call interface to the 'LXRT' , the user space API of RTAI could be integrated into LabVIEW for Linux. By this extension it is now possible to perform with hard real-time using graphical user space programming. The visual data flow programming of LabVIEW easily visualizes timing and synchronization dependencies. Although the full LXRT API hasn't been implemented yet, a basic set of timing and data acquisition functions for hard real-time are shown to be working. A jitter as low as five microseconds on a Pentium III/500MHz makes it possible to have 20 kHz loops with sophisticated computing, e.g. PID closed loop control and audio filtering, by just doing graphical programming. This is another example of the power of the LXRT user space API of the Real Time Application Interface for Linux, giving us the possibility to do hard real-time from user space.

Read full paper (PDF download)

 
This article was originally published on LinuxDevices.com and has been donated to the open source community by QuinStreet Inc. Please visit LinuxToday.com for up-to-date news and articles about Linux and open source.