Real Time Data Acquisition and Control

This paper presents a laboratory environment for the development of real time data acquisition and control on the IBM-PC platform. The laboratory station involves the integration of low-cost computer technology with powerful software components which empower the student to efficiently and effectively construct real time systems. The software base integrates an editor, a spreadsheet, and a real time programming environment built around Druma FORTH. We have written multiple FORTH libraries to assist the student in the translation of engineering concept into creation. Real time events are managed using a rich set of FORTH software routines which guarantee that time-critical software is executed on schedule. The real time color-VGA graphic library includes many types of windows. We have developed an extendible debugging tool called PROSYM (PROfiler and SYMbolic debugger.) PROSYM provides a simple set of primitives with a high expressive power that may be used singly or may be combined to construct customized debugging tools. In addition to providing basic debugging functions, PROSYM supports an event-action model of debugging. We have evaluated this development system on the full range of PC platforms from the original PC-XT to the newest 486 systems. The environment has been used for two years by Biomedical and Electrical Engineering graduate students performing both teaching and research projects. Introduction The purpose of any laboratory experience is allow the student to develop, apply and evaluate engineering concepts in a practical manner. A well-organized laboratory course can be an effective teaching experience, while a poorly-run lab will cause undue hardship on both the student and the faculty. We have attempted to assemble the hardware and software components for a graduate level class on real time data acquisition and control. The class combines both Electrical and Biomedical Engineering aspects as shown in Table 1. Electrical Engineering Biomedical Engineering • microcomputer interfacing • medical instrumentation • real time data acquisition • signal processing • analog instrumentation • transducer physics • control systems • patient safety • quality programming • effective human interfaces Table 1. The objectives of the class involve the integration of EE and BME disciplines. The key is to provide sufficient tools (with appropriate documentation) so that the student can quickly and effectively deal with the fundamental educational issues of the class (Table 1) without being overwhelmed with the complexities of the machine. On the other hand, we feel that complete isolation from the computer, as is the case with National Instruments Labview, inhibits the student from dealing with the Electrical Engineering aspects of the instrument. This problem is accentuated when the details of the hardware/software interface play a critical role in the engineering design decision. In the educational setting, it is particularly important for the student to have the power and control to manipulate the computer so that the trial and error experimental process of learning is Real Time Data Acquisition and Control Valvano, Ahmad, Nayak ASEE Austin, TX May 7, 1999 Page 2 allowed to flow smoothly. In addition to control, there must be facilities for performance evaluation, so that the student can effectively compare and contrast alternative designs. What is FORTH? C.L. Moore created FORTH in 1972 as a programming language to control his telescope. Moore chose the name FORTH because he considered it to be a fourth generation programming language. Our FORTH is more than a programming language, it is an integrated software environment including an editor, an Intel 80x86 assembler, high level language compiler, interpreter, debugger, real time graphics, floating point, file system and real time operating system. The FORTH environment is efficient for the development of real time instrumentation and embedded-control systems. The FORTH interpreter, along with its simple structure, facilitate programming for the beginner as well as the experienced software engineer. FORTH provides links to any editor on the PC. The editor is used to create and modify user programs. The FORTH compiler can then be invoked to produce new definitions with fast execution speeds. Even on a modest computer (12MHz 286), the edit/compile/download/run programming cycle is as fast as 20 seconds. The interpreter can be used to develop and test new functions. The interpreter allows for effective interaction between the student and the machine. The program development stage can be operated under DOS or Windows. In the real time execution phase however, the system runs only under DOS. This is because the scheduling of real time events can not be guaranteed under Windows. The real power of FORTH comes from its inherent extendibility. The user is provided with an initial set of language elements, and the ability to add new elements to the working set. The true beauty of FORTH programming lies in the fact that one has complete control over the computer hardware (e.g., I/O devices written in assembly language) but still has a rich and extensible set of high level language constructs. FORTH provides links to any executable program on the PC (e.g., editors, spread sheets, networks.) Typically students transmit data into a spreadsheet (including those on the Macintosh) for analysis and report generation. The version of FORTH that is used in our lab was developed at Druma Inc. of Austin Texas. One of the truly exiting aspects of Druma FORTH is its debugger, which is described later. Table 2 gives a list of library routines available.