Poor Mans DDS Board

Posted on Feb 6, 2014

The applied microcontroller is an ATMega8 clocked at 16MHz. This microcontoller can shift out arbitrary wavefroms from its flash or SRAM storage at a rate of 2MS/s (and even faster!). The 8bit data is fed from portD to the AD converter ( Analog `s AD7524) connected as voltage DAC. The USB data lines are shared with the DA data forming a common 8bi

Poor Mans DDS Board
Click here to download the full size of the above Circuit.

t bus, hence you cannot update the analog output while talking over the USB and vice versa but fortunately, the AD7524 has an internal latch so that it can keep the previous analog value. USB_CTL provides the 4 necessary USB control lines. JP2 provides 3 dedicated user IO lines. These can be freely used e. g. as trigger or status indicators. Note that two of these lines are connected to portC an hence can also be programmed as inputs to the ATMega8 on-board AD converter. Of course, if you don`t use USB, you have additional 4 arbitrary IO lines. And then, there`s LED1, a freely programmable general purpose diagnosis LED. (Very handy, you`ll see. ) Note that this is an updated revision of the circuit. The photos show exactly that revision but it was manually changed after PCB fabrication. This is why the board has e. g. two unused potentiometers.

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