PWM and audio noise

[keithv]

Software wise you might try increasing the frequency you're using for your PWM. Above 20kHz the ear can't really hear it. The PBP3 Reference Manual sets a 32767 Hz upper limit for the HPWM command. Working the CCP & TMR2 registers manually, you may be able to go higher.

I was hoping there was a solution in the software and not the hardware. I've seen other similar projects where they used the same PIC16F684 but used a 20MHz external crystal higher frequencies.

[Scampy]

I'm no expert, but most analogue audio signals alternate between + and - rails and thus are not "grounded" in the same way as supply rails. But you have said that separating them hasn't resolved the problem. Possibly some grounded shielding over the PIC to prevent RF interference might help

[Charlie]

This is always caused by either the design or layout. Post the schematic and layout if you really want an answer.

[Art]

You haven’t described what you’re doing, or how the RF relates to the PWM.
For all we know you’re clocking a pic at 10MHz and sending the audio out of a 10MHz WWV receiver through audio on the board.

[Normnet]

A simple software change to try is to rearrange the order of the variables as they are declared. This worked for me although on a different compiler the app did utilize PWM as an audio output. Hope this helps.

Norm