Signal generator is a must have tool for every electronics engineer and amateur. Not everyone can or want to buy signal generator that costs much. If your needs aren’t very high you can build signal generator by yourself from few common electronics parts.
ScienceProg developed very good alternative which is really simple to build but have great functionality. This is a software based DDS signal generator which runs on Atmega16 microcontroller and can generate sine, square, triangle, saw tooth, reverse saw tooth, ECG, noise signals in frequency range from 0 to 65534Hz. It also has signal offset and amplitude regulator. So you can get up to 10V signals. Signal generator has also distinct High Speed (HS) output were high frequency (from 1 to 8MHz) signals can be generated. Ideal tool to have on a workbench. WinAVR source code and Eagle CAD files are available for download.