CalibFreq / OSCTUNE

[whiteoaks7]

Do the magic numbers that follow the 'calibfreq' command relate to anything? Are they, for example, a percentage change or ppm or a number of clock cycles at the given frequency. Given that I want to change the clock on my project by 1% knowing what the numbers mean would be useful. I've checked both the picaxe and pic manuals and neither of them are definitive.

 

[Buzby]

The numbers are not definitive, different chips will give different results.

IIRC the numbers adjust the loading on the resonator, thus making it a bit faster or slower.

You would need to do some repeated 'adjust and measure' trials to get an exact value.

See : ww1.microchip.com/downloads/en/AppNotes/00244a.pdf

 

[AllyCat]

Hi,

I don't think that the PICaxe Manual is even correct for recent devices. It specifies -16 to +15 but I found that -32 to +31 would work.

I believe that each step is less than 0.1% for M2 devices.

Cheers, Alan.