Wednesday, April 20, 2016

AD9850 DDS with ARDUINO

10 Hz  to 51.000000  MHz , steps selectable 1Hz  to 100kH or 1 Mhz

I had this AD9850 unit some time waiting to test it.
I used an ARDUINO UNO  with LCD Keypad shield
And a rotary encoder.

Many HAM 's already build receivers and tranceivers based on this fantastic AD9850 as VFO.
With this AD9850  building a rock stable VFO became a piece of cake!

The ARDUINO website shows many projects with this AD9850
But I could not find a sketch that  fitted my setup 100%.
I used the rotary encoder improved interrupt sketch as first base
by Simon Merrett / Oleg Mazurov / Nick Gammon rt Steve Spence

First only down count worked  I had  the encoder at pin 1 and 2  not 2 and 3  since those pins are  shifted 1 position on the board that tricked me.

Also the Vcc had to be connected to this encoder.
Only enabling the internal pull-up R's on the pins 2 and 3 showed missing pulses.

Had to adapt some things
The main loop was only a 1 time loop in fact in the original sketch

The LCD Keypad shield uses the pins 4 5 6 7 8 9  for the LCD    and AD0 for the keys
But AD1 2 3 4 5   and  D2 and D3 where left free
ATmega328  free AD inputs can be used as GPIO real nice

Some struggle to get the encoder to work. At first only rubbish came out.

But then it worked stable pulsing up and down and  functions to the main loop for displaying and controlling the DSS VFO where added.

 10Hz  to 51  MHz!  steps adjustable 1Hz ! to 100kH or 1 Mhz
all as you please!
and  I could tune calibrate it to my K3 that is very stable and precise at  frequency.

this is the sketch it works but needs more features

https://www.dropbox.com/s/zx5ea67oxqjd979/ad9850.ino?dl=0





  





3 comments:

Razvan YO9IRF said...

Hello Jaap,

I did something similar a few years back. Unfortunately the AD9850 is not that good over ~20MHz, receiver will be noisy and will have spurs. Si5351 should be a better solution.

Cheers,
Razvan YO9IRF/M0HZH

Jaap van oosten said...

thanks for your comment

it was nice to play a bit with this device and Arduino

noise is bad
that rules this DDS out for serious TRX work then
maybe it is still useful for lower bands


will have to get the Si5351 next
the QRP labs U3 uses the Si5351

Raymond Brooks said...

Was interested in trying this dds control cerkit but the link to the sketch
https://www.dropbox.com/s/zx5ea67oxqjd979/ad9850.ino?dl=0
Is not working

73 Ray g8kps

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