Build Your Own μC-Based Function Generator: Part 1
by Dennis L Feucht
This month we begin a new project that returns to the theme of function generators (FGs). The FG continues to be a major test and measurement (T&M) instrument, along with oscilloscopes and DMMs, because it is a versatile waveform source. It is essentially a triangle wave generator that uses a square wave to do generator switching. The third waveform, the sine wave, is shaped from the triangle wave. FM, AM, and gating of the generated waveforms are easily accomplished. With μC control, it becomes even more versatile.
The FG506 sweeping function generator of a previous project was designed in the style of T&M instruments before the use of microcontrollers – roughly before 1980. This project advances from that stage of technology to the early 1980s, when T&M instruments were beginning to be designed as peripheral plug-in cards for early desktop computers such as the IBM PC and the Apple II. While in Tek Labs (once the research sector of Tektronix), I was approached by a group manager who had in mind to start a T&M instrument company based on the Apple II. I had, on the side, designed a prototype instrument that caught his attention, and he invited me to become involved. The Northwest Instruments FG card for the Apple II computer resulted.
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