I have been trying to program cheap Chinese DDS modules recently. I wanted to add a DDS VFO to one of my bitx rigs. These modules are available at $4.5 from aliexpress. They claim that it can work up to 40Mhz.
I used an arduino Uno along with a rotary encoder for controlling the module. The DDS module pin out is shown below.
The connections to arduino and rotary encoder is shown below.
You can download the code hosted on github from here.
The code is for 40m VFO with IF of 9Mhz. You can easily modify it for other bands and IFs. Additional functions can be programmed easily.
The DDS modules are available on line form from many sources. The rotary encoder can be obtained from element14.