PC Strip-Chart

Year of completion: 1993
Purchased/Utilized By:
OMEGA Engineering

                                     Mail order, catalog sales
Application: Data Acquisition

The idea was to use rarely known features of VGA/SVGA cards to make the computer screen behave as very fast strip-chart recorder (Real-time data traces displayed from bottom-up). If standard graphics libraries were used, the scrolling of the screen would require moving the contents of the entire video memory with every 1-row scroll. Instead, by using the VGA registers which allow defining the beginning of the video buffer, and writing custom VGA graphics library, I implemented a sort of circular video buffer in the video memory. As the result, the scrolling of the screen to display a new set of values required very little processing power and resulted in ability to display the real-time data as fast as 50 screens per second (on a 486 computer).

Another challenging feature of the software was to make data streaming to the disk continuous and simultaneous with acquiring and displaying the data, all at very high rates (up to 100,000 samples per second per channel). This was accomplished with a special real-data buffer design which dealt with different speeds of the data-acquisition hardware, the display routines, and the hard-drive.

This was a complete, commercial package that was sold by OMEGA Engineering (the largest USA distributor of data-acquisition equipment), by some hardware manufacturers, and by mail order. As such, it had to support all popular video cards and printers.

The full demonstration of the software would require a supported data-acquisition card. It is however still possible to test the software without such card, since a signal simulation driver is implemented in the software.

The software was written in C++ and the assembly language.