On Fri, 24 Apr 1998 04:26:45 +0100 Leon Heller
<leon@LFHELLER.DEMON.CO.UK> writes:

>This is trivial if you use a DDS chip like the AD9850, I have a web
>page
>describing a simple AD9850 system. The device actually generates a
>sine
>wave, but has on-chip circuitry to convert the output to a square
>wave.

You need only the "counter" part of a DDS system (leave off the sine wave
table and DAC) to generate approximately square waves.  The "on-chip
converter" is likely just the MSB of the phase accumulator brought out to
a pin.  (Somewhat better results could be had by analog filtering the
sine wave and comparing it to zero.  This would help interpolate the
edges of the square wave between sample points)

At lower frequencies (up to maybe 50 KHz) DDS is possible with PIC
software (Ob PIC).

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