Using Hidkeys with internal RC oscillator? (on atmega8L?)

beau · Post by **beau** » Thu Apr 17, 2008 9:13 am

Howdy.

Is it possible to change the hidkeys project to run of the internal oscillator?.

I want to build one, then modify it and learn how it works, but i can't find 12MHZ crystals anywhere near me.

Cheers

Post by **christian** » Thu Apr 17, 2008 9:30 am

Can you get 15 or 16 MHz? The Mega8 has no 16 MHz RC oscillator option. You may have success with calibrating the RC oscillator to 12 MHz, but that's not reliable.

Guest · Post by **Guest** » Thu Apr 17, 2008 1:12 pm

local store doesn't have 15 or 16Mhz crystals at all it seems.

They stock 8,10 then it jumps to 20Mhz. I think 20Mhz is too high for the mega8 to run properly.

would it be possible to use a 10, 8 or 6 mhz crystal? or are these to slow?

Post by **christian** » Thu Apr 17, 2008 2:47 pm

You need exactly one of the supported values which are 12, 15, 16 and 16.5. A module for 20 MHz is planned, but not yet available.

Guest · Post by **Guest** » Fri Apr 18, 2008 7:39 am

So it's not possible to get it working with the internal oscillator? (it says on the main page some micros work with it).

If so i'll just see what i can find from the net lol.

Cheers

Post by **christian** » Fri Apr 18, 2008 1:37 pm

You can try tuning the RC oscillator to 12 MHz. I had success on a test board. But the spec says that it should not work reliably.

See the EasyLogger example. Copy the oscillator calibration from there and set F_CPU to 12 MHz. The oscillator should then be calibrated to 12 MHz. If it works, you can use it until your crystals arrive.