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Low-Cost, Two-Channel Scriptable Waveform Generator

Microcontroller addict [Debraj] decided to make his own programmable sine wave generator, and was able to put it together for under $40 USD. Other than low-cost, his list of requirements was as follows:

  • Dual sine wave output, synchronized
  • Frequency, Amplitude, and Phase control
  • Low harmonics under 1 MHz
  • Scriptable via Python

The heart of the project is the Analog Devices AD9833, a complete Direct Digital Synthesis (DDS) waveform generator system on a chip. If you’ve ever rolled your own DDS using discrete ICs or in an FPGA, you can appreciate the benefit of squeezing the phase accumulator, sine lookup table, DAC, and control logic all into a single ten-pin package. [Debraj] uses AD9833 modules from the usual online vendors for a few dollars each. He synchronizes the generators by disconnecting the reference crystal on the second module and driving it from the first one. The remaining specifications are met by the inherent characteristics of the DDS system, and the scriptable interface is accomplished with an Arduino controlling the AD9833 chips and two programmable gain amplifiers (MCP6S31). We like the confidence that [Debraj] displays by sketching the initial circuit diagram with a ball-point pen — check out the sketch and the final pictorial schematic in the video below the break.

This is a good example of combining off-the-shelf modules to quickly build a project. This approach is great for one-off builds or as a proof-of-concept test bed that can later be spun onto a custom PCB. Another reason to use modules these days is that the modules are often in-stock but the chips are unobtainable. Though it appears [Debraj]’s only needs one of these generators, it would be an easy board to layout and build — if you can buy the parts.

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