PWM_triangle_ctrxbeat

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By: Tracy Allen, created: 2016-04-11 | updated: 2016-04-11
-- Generates conventional PWM that increases and decreases linearly with time
-- Can be filtered to a triangle waveform
-- Uses 2 cog counters in NCO mode directed to the  same output pin, long cycle at the beat frequency
   No program loops required for basic operation, cog counters only.
-- Counters in a second cog can provide inverted output,
   and also a lower frequency square wave synchronized to the beat frequency
-- Operation can be viewed on an oscillosope, probes connected to
      pin     main output is PWM varying from 50% to 100% high at the selected frequency
      pin+1    inverse of pin, varies between 0% and 50%
      pin+2    low frequency square wave at that flip flops at the inflection points
-- The second cog is not needed unless you need the inverted signal and/or the beat frequency
   In an applicaton, the second set of cog counters can be patched into an existing cog that does not otherwise need its counter modules.
-- Also see http://obex.parallax.com/object/482, method to set fixed frequency and duty cycle PWM with counters.
 
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