This project describes howto create a waveform generator with an AVR Microcontroller and an Analog Devices DDS circuit.
The AD9833 is a programmable waveform generator capable of producing sine, triangular and square wave output signals up to 12.5 MHz (clocked with 25MHz).
The Interface Boards contains all basic components the DDS Chips needs to run. If you compare the component count with that of a MAX038 circuit you will see, that there are less here.
In the top-corner of the board you find the power connector (“Key Lock”). Next to it the BNC Connector for the Output signal. The 3-pin connector for the serial interface is located at the bottom of the Board. For a first basic test of operation connect the serial interface to your computers parallel port and use the software provided by Analog Devices (the schematic for the parallel port connection can be found in the AD9833 Datasheet. You can connect the pins directly without the use of the 74HC744 8bit Latch).
The AD5932 can be seen as the next generation of the AD9833. The max. Outputfrequency has been doubled and additional Pins have been added. The AD5932 can produce sine, triangular and square waves from 0 to 25MHz with 28bit resolution.
Creating a programmable Gain Amplifier (PGA):
The get a full functional waveform generator some analog parts to adjust Amplitude and Offset are required. This is the really tricky part of the project. If’ve started with two OPAMPS and a Digipoti to get a PGA (I haven’t tested my circuit by now). At the moment i’m thinking of using the VCA810 from TI, some OPAMPS and maybe a Digipoti or an voltage output DAC.
Downloads / Schematics:
AD9833 Interface Board:
AD5932 Board with PGA: