Sunday, 30 August 2015

AD9850 DDS module and controller working

After successfully getting the DDS controller PIC and its 2 line LCD up and running yesterday, today I rejigged the breadboard to fit the AD9850 DDS module on. The PIC talks to this via an SPI serial bus, and the module gives two square wave and two sine wave outputs at the programmed frequency.

At first, it seemed that it would only give the right frequency above 14MHz! Anything below becoming progressively more inaccurate, until around 5MHz where it was all over the place!

After a nice hot bath, and a bit of a think, I went back and gave the frequency counter a bit of a kick! I realised it was the counter that was playing up, not the DDS module! A bit of fiddling with the input ports, the range switch and the trigger level and I proved the output of the DDS on all the controllers 'standard' frequencies, which are all within the amateur bands, this including 500kHz and 137kHz!
I just need to add the encoder now and some real buttons!

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