Digital Sweep and Sinewave Generator with direct frequency entry
Published in issue 391, July/August 2009
The Parallax SX28-based ‘Frequency Response Sweep Oscillator’ project published in the April 2008 issue of Elektor inspired the author to develop a similar circuit based on the ATmega48 microcontroller. As it turns out, the ATmega-based circuit is nearly as capable as the original. An important characteristic of the design is the maximum direct digital synthesis (DDS) sample rate that can be achieved when generating a sinewave.
Characteristics * Digital sweep function: Frequency ranges: 100 Hz to 100 000 Hz or 50 Hz to 15 000 Hz, logarithmic scale with 256 steps 2 sweep rates: 0.2 ms or 0.4 ms per frequency value (phase accumulator increment value changed every 0.2 ms or 0.4 ms) Outputs in sweep mode: * sine output * marker frequency (rectangular wave) * marker position pulse * trigger pulse at start of each sweep
* Digital sinewave operation: Direct frequency entry in Hertz via keypad Format: '*' = start of entry digit(s) 0 to 9 '#' = end of entry, start sinewave generator Outputs in sinewave mode: * sine output (0 VPP to 4.5 VPP) * frequency/marker pulse (rectangular wave)
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Please note. In view of the complexity of international markets, Elektor cannot guarantee the availability of components for this project.
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