Changing the sines frequency?

[pxidr84]

Okay, so I've unsoldered an 8MHz xtal (not an 10MHz unfortunately) on a old board, and I connected this one to the PIC.
I've enabled the PLL, so my PIC clocks at 8*4=32MHz.

On the oscilloscope, I get now a 2µs pulse, it's a little better.

[HenrikOlsson]

Now it seems to run properly - finally.

In order to make the calculations of the preload value match your new (32MHz) oscillator speed you need to change the Dummy2 value from 10000 to 8000.

Then keep the same test code in the interrupt service routine and try with InterruptFrequency = 10800, check the scope, there should now be pulses at 10800 or likely a little bit slower.

The reason it's not 10800 exactly is, again, due to time that the timer is actually stopped while reloading it. To tune it simply tweak the +1 in the following line:

TimerReload = 65535 - TimerReload + 1

Try +12 or something and see what happens.

Then try adding code to your interrupt, not all at once, add it in little by little and keep an eye on the scope. If you start to see jitter or "missed" pulses then you're "overloading" the PIC - ie interrupting to fast. Keep the code in the ISR as tight and short and possible. Think thru it, is there any other way to achive this or that to make this execute faster. Every cycle counts here. Verify with the scope, the pulsewidth shows the execution time of the ISR.

Trying to make a 3-phase inverter when you're new to PICs are quite a challange - as you probably/hopefully know by now - take baby steps.

[pxidr84]

Hurray, now I got something who works flawlessly.

I've played with the dummy values (Dummy2=8745 and Dummy3=100), now I get the exact sines I want.

For 1200 for example (120*10=120.0Hz), I get 120Hz, for 500 (50*10=50.0Hz) I get 50Hz, for 357 (35.7*10=35.7Hz) I get 35.7Hz...

So now it works, I can go ahead in my project.

Thanks a lot Henrik for your help and your support.

[HenrikOlsson]

Great!

I have no idea why you changed the Dummy2 and Dummy3 variables as you did (8750 and 100 (?) ) But then again, as long as it works for you....

Good luck with the rest of the project!