I have bought a couple of AD9850 DDS boards on ebay.
I have tried two and they are quite fickle. A third one seems to be working OK, so far.
The setup is very simple: connect to an Arduino Pro Mini, and set it to oscillate at some low frequency, eg 200KHz.
When it works I get a +/-500mV sinewave output.
When it does not work, depending on the board I get either 0V or 500mV constant (no wave).
The arduino code uploads the desired frequency a couple of seconds past startup, and does nothing after that.
What I have noticed is that the dodgy AD9850 boards will sometimes start producing the wave 5-10 seconds past startup. Other times flicking the Vcc line on the AD9850 enables the output, as if something was holding the output disabled all this time.
Has anyone seen this, and know what it may be? Is there some sort of "enable" / "disable" output command that I am not sending maybe and that keeps some flag in an unitialised state in the AD9850 maybe?