Multiple PWM and port C

[Scampy]

I've recorded the wave form when using the hardware PWM modules on the chip to explain the issue I'm getting.



If you compare this to using the multi_swpm file and port D you notice there are loads of spikes in the HWPM signal and some harmonics ? - the amplitude is also a lot less (I had to increase the volume for the HWPM to get a similar trace)

[HenrikOlsson]

As I've said a couple of times now:
You can not run the hardware PWM at a frequency below 1221Hz - it's not a bug in PBP and not a hardware issue with the PIC or the circuit, it's just the way it is.

The reason is because TMR2, which is used for the PWM timebase is 8 bits wide and has a prescaler with a maximum ratio of 1:16. At 20MHz the timer ticks at 5MHz, so 5,000,000/256/16=1220.7Hz. If you try anything lower than that it will not work properly and I'm pretty sure that's what you're seeing when trying to run it at 200Hz.

To prove or disprove, try it again at 1500Hz and see if the waveform looks better. I understand that it won't work in your particular application due to the LED drivers but it'll show that actual problem is that you're trying to run the PWM at a frequency (200Hz) which the module is incapable of producing.

/Henrik.