modulating carriers
So I'm curious: how would we go about modulating a carrier (presumably generated by one of the magic counters) with the output of another COG?
I suppose FM modulation is just manipulating the phase register, right? But I'm not sure how to go about amplitude modulation . . .
I suppose FM modulation is just manipulating the phase register, right? But I'm not sure how to go about amplitude modulation . . .
Comments
For AM, set either NCO or PLL mode and write the appropriate frequency value into FRQ. Then, perhaps using the other counter,·PWM the same pin at a much lower rate (or maybe toggle the DIR bit to modulate the drive), so that over brief periods you will get·averages of continuous-wave·vs DC output. This will demodulate to analog AM levels.
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Chip Gracey
Parallax, Inc.
How about the broadcast TV demo? For this, the output frequency is probably much too high for this to work; you must have come up with something else in order to drive the phase-shifted chroma modulation onto the broadcast carrier.
Man, this propeller plus some limited external circuitry may *possibly* even make a pretty cool software-controlled radio. Think superheterodyne with a completely software-driven IF. Of course you'd probably have to be very careful so the EMI from the processor didn't kill your signal, but what fun!
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1+1=10
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Chip Gracey
Parallax, Inc.