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Return to BlogDDS Board Built in Simple Design
Posted Feb 08, 2012 at 1:57 pm
Figure 1
The project features an AVR RISC microcontroller connected to a D/A converter in order to build a simple DDS-type board.
A straightforward design is implemented in this project where an 8-bit parallel input D/A converter is taken and the 8 data lines are connected to the microcontroller’s 8-bit I/O port. In addition to the connections are the control lines and supplying a buffer amplifier. A stabilized voltage reference and an output attenuator are ideally used for a real DDS but this design is kept simple.
An ATmega8 microcontroller running at 16MHz is used since arbitrary waveforms can be shifted out from its flash or SRAM storage at a rate of 2ms. Port D provides the 8-bit data to the A/D converter AD7524 connected as voltage DAC. A common 8-bit bus is formed by the USB data lines that are shared with the D/A data. The AD7524 has an internal latch in order to keep the previous analog value although the analog output cannot be updated while talking over the USB and vice versa.
Three dedicated user I/O lines are provided by JP2 to be used freely such as status or trigger indicators.
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