Been blog-silent for a while, but my AD9850 DDS is now complete. The Arduino (Nano) code evolved day-by-day while assembling the circuit. I re-assigned some pins to simplify wire routing and implemented an easily extensible menu. My code is based on AD7C work and it is available on request.
I have added a scan function with user settable lower/upper frequency limits.
I have added a menu driven with a resistive potentiometer, which requires only one button for confirming the action and theoretically can host dozens of functions. While it is not an innovative idea, it is very comfortable to use as long as there are 5-to-10 total choices.
I am now using a TWI/I2C interface to the display, which uses 4 instead of 8 total wires.
DC is provided with a step-down regulator. I will add DC filtering capacitors near the Arduino and DDS boards.
That's two knobs and one display that now require a suitable housing.