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OUT OF YOUR HANDS

A PC Interface for Hand-Held Devices
by Kock Kin Ko

Start • Creating GUI and Menu • PC Interface Software • CVI Windows Programming Basics • Working Together • Plotting Performance Graphs • How Serial Com Operates • Big Endian Data Becomes Little • Sources and PDF 

This article is a complementary part to "Vehicle Performance Analyzer," which will be appearing in issue 110, the September issue of Circuit Cellar magazine. In that article, I touched on how data records can be uploaded from the Hitachi microcontroller H8/3644 (used in the vehicle-performance analyzer project) to PC through an RS-232 link. Because this uploading of data has recently become a ubiquitous feature that can be found in quite a number of hand-held products, I felt that the topic deserved a little more attention.

This article addresses how to use C Virtual Instrument in developing the serial-communication PC interface software for hand-held products such as digital cameras. The software development includes designing a graphical user interface, setting up serial communication, converting data in different Endian formats, and plotting graphs.

WHAT IS VIRTUAL INSTRUMENT?

A virtual instrument is a piece of software that allows a PC to integrate different instruments into a system for the purpose of measurement and control. Why is it called virtual? Consider this example. With home instruments such as a scanner and a printer connected to a PC, you can turn a PC into a photocopier. Of course, your desktop machine didn’t "morph" into an actual copier, it would be more accurate to say that the software is the virtual instrument.

C Virtual Instrument is a development software package from National Instrument USA that is used for designing virtual instruments. The process of generating a CVI Windows program includes three steps: designing a GUI, auto-generating program framework from the GUI, and filling in user-function code details in the program framework.

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