PWM_triangle_ctrxbeat

-- 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.