Build a PIC controlled DDS VFO, 0 to 6 MHz

Click a picture to zoom
Top side of prototypeBottom side of prototype

Files contained in MINIDDS.ZIP:
  readme.txt      Read this first!  compplac.pdf    Component placement in PDF format  schema.pdf      Schematic diagram in PDF format          PCB top copper layer in Postscript format       PCB bottom copper layer in Postscript format  ad9832_4.asm    PIC assembly source code      Needed for assembly of ad9832_4.asm (for 'F84)      As above but for 'C84  vfo5x7f.hex     PIC16F84 program for LCD with 5x7 font  vfo5x10f.hex    PIC16F84 program for LCD with 5x10 font  vfo5x7c.hex     PIC16C84 program for LCD with 5x7 font  vfo5x10c.hex    PIC16C84 program for LCD with 5x10 font  filtresp.pcx    Computed frequency response of lowpass filter
Download MINIDDS.ZIP (186K)

Download MINIDDS.PDF (209K)

If you prefer to control the DDS module from a PC (instead of using a PIC), try this:

Download PCVFO.ZIP (18K)

The zip archive contains a single file, VFO.EXE. It is a DOS program but it runs fine in a Windows 95/98 "DOS bubble" as well (see screenshots above).

Are you looking for a DDS based 136 kHz longwave transmitter exciter?

Have a look at G0MRF's page


Schematic and source code for the PIC controller is available here:

Download the PIC program

The PIC program is written for the free version of the CC5X C compiler which is available

Click for full size schematic!

Click the schematic for a full size version

Almost any 2x16 character LCD module with Hitachi HD44780 controller chip will work.The LCD pin numbers on the schematic are not valid for all LCD modules. Please checkthe actual signal names on your particular LCD module.

The selected DFCW frequency offset will be added to the output frequency when theDFCW input is grounded. This input has a weak pull-up in the PIC.

The encoder inputs also have internal pull-ups in the PIC.

The switches "LOCK", "DFCW" and "CAL" are momentary pushbuttons.

Back to main page

Hit count: 34959