DDS Arduino AD9850

I have build a DDS generator with a Arduino Pro Mini and a cheap AD9850 module.
Both can easily be found on ebay.
It is based on a description by AD7C.

By the push button you select the tuning steps:
10 Hz, 50Hz, 100 Hz, 500 Hz, 1 kHz, 2.5 kHz, 5 kHz, 10 kHz, 100 kHz, 1 MHz.
With the encoder you adjust the frequency between 1-30 MHz.

The output is terrible! Very much distortion and harmonics.
Others say this circuit works great, maybe I did something wrong.
So I never got this finished by building it into an enclosure.

Update 18.03.2018:
I made some changes to the SW so the screen looks like this:

I changed the step rates so only these are available: 10 Hz, 100 Hz, 1 KHz, 10 KHz, 100 KHz and 1 MHz.
I added a push button so the step rate can be changed up and down,
I added a arrow up in line 2 to show which figure is changd by the encoder.

Here you find my schematic, (Eagle), still only 5V supply and no 12V regulator.

The output still is horribel and only noise is heard on the seleected frequency, not a sinus tone.
Se some oscilloscope pictures, my AD9850 must be broken, maybe I should buy a new one:

You can download my arduino scetch: dds_ad9850. (ino file in zip format).

Here is a much better solution than mine 🙂


Min nye hjemmeside