I've uploaded my sketch for the N5IB Experimenter's board for the Nano and cheap DDS module. It's in a new folder called Experimenter's Sketch WA5BDU, I think.
I chose to go with a minimal configuration using three pushbutton switches for input and a tiny speaker for output via Morse to the user.
In its simplest mode, one switch causes the frequency to be annunciated and the other two give a Step Up and Step Down frequency change function.
By holding down the annunciator button, a list of menu options will be played. This is similar to the approach used in Steve Weber's ATS-3 and Dan Tayloe's Stinger Singer frequency counter. You release the button on hearing the desired option.
I store band (actually, just ten frequencies) data and step size in EEPROM.
Functions available now are-
Change step size
Send repetitive message in Morse via RF output
Turn RF output Off and back On
Store current frequency to 'scratch pad" EEPROM memory, and recall same
Annunciate current frequency
Step frequency up or down
My notion is to put this thing in a fairly tight box with a battery so I can use it as a signal source with minimal leakage - hence no display and no cables except RF out.
A little tweaking of the source code is required. First, there's a flag for AD9850 or AD9851 versions. Also, there are routines that do a "one time" write to EEPROM to establish band data and so on. You'll typically let them run on first loading and then comment them out so they don't run every time you start the program.
Details are in the PDF in the same folder.