AD9833 – Programmable Waveform Generator

[Catcatcat]

Recently acquired two modules on the AD9833 - Programmable Waveform Generator. I made myself a simple low-frequency generator and decided to share the circuit and firmware. The generator can form a sine wave, a triangle signal and a square wave. It is possible to select a discreteness setting frequency. Two frequency setting ranges, roughly and smoothly (with a predetermined resolution). You can adjust the output amplitude of a sine wave and a triangle signal. The meander goes straight through the switch. Collected, on what was at hand. Tips for work in three languages, English, Ukrainian, Russian are embedded.

Work with the generator watch the video. https://youtu.be/ZSAUzkyPoK0

Scheme in pdf format and firmware in the attachment:

[PICker]

My compliments for this very interesting project.
What is the frequency range and maximum amplitude (peak-to-peak) of the output?
The output coupling seems to be a DC coupling, is it possible to set 0 Hz as output frequency and set the output voltage (for using it as stable DC voltage source) ?

[Catcatcat]

Yes, you can set 0 Hz. The frequency step can be 0.1 hertz. It is possible to set the maximum available frequency, but MCP601 will miss up to 1 MHz with such a factor. Maximum amplitude up to 3 volts.

[TucoRamirez]

Nice job.


I'm wondering how to perform with some precision the following task on two ranges:  (0-100Hz)  and (20k-50kHz)

to set a Fo frequency and amplitude
then output an n number of signal periods accurately (in order to perform a FFT only on that cycles)

I tried to approximate with delays but i still have errors    

[Catcatcat]

As far as I understand in the FFT, in order to determine the frequencies in the range, for example, 20 Hertz, it is necessary to scan a signal with a duration of 1/f, i.e. 0.05 seconds. Those. the lower you want to determine the frequency, the longer the scan period. For normal frequency determination, it is necessary that at least one full frequency period fit into the scan data.
Frequencies that are “higher” than the FFT capability will be superimposed “flipped” onto the main spectrum.

I apologize for my “French” using a translator.

[Catcatcat]

At the request of the developers of automatic systems of music light synthesizers, added the function of selecting a frequency for a note number.

[Catcatcat]

Version 3.01

Fixed some drawbacks of drawing graphics.