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Electronics -- Poor Man's DDS Board

An extremely simple 8bit, 2MS/s direct digital synthesis (DDS) board.

Overview

Poor Man's DDS board image (top) [8kb]
[click to enlarge: 101kb JPEG]

Except for the pluggable USB8Bit board, this is among the simplest DDS-type boards which can possibly be built: Basically, it's just an AVR RISC microcontroller connected to a DA converter.

Features:

  • 8bit DA converter and fast R2R output buffer.
  • Up to 2MS/s (million samples per second).
  • Single 5V supply or USB-powered.
  • 3 dedicated user-configurable IO ports (e.g. trigger input, sweep output, AD converter) and a diagnosis LED.
  • USB connection for waveform download via USB8Bit board.
  • 8kb flash and 512 bytes SRAM, freely programmable 16MHz microcontroller.
  • USB-powered and externally powered operation.

Poor Man's DDS board image (bottom) [8kb]
[click to enlarge: 107kb JPEG]

Yes, just 512 bytes of SRAM does not look like much but if you want to output a sinus or a sawtooth, you can put the tables statically into the flash storage and for more complex output, the microcontroller can be be freely programmed...

Electronic Circuit

The design is straightforward: Take an 8bit parallel input DA converter and connect the 8 data lines to an 8bit IO port on the microcontroller. Additionally, wire up the control lines, supply a buffer amplifier and you're done.

Of course, for a real DDS you'd like to use a stabilized voltage reference and an output attenutator but this is deliberately kept simple.

The full schematic and more information is on a separate page.

Host Software and Firmware

Currently, no software is published here, sorry.
I'm using specialized host software and firmware for certain tasks (which also make use of the AD converter in the PoorManDDS) but these are not suitable for publication.


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Last modified: 2006-08-19 14:38:36