# Fuse Q. Which Crystal option?

I'm planning on using this crystal but don't know which type it is (Low-Freq or Full-Swing) as far as setting fuses are concerned.

http://www.ctscorp.com/components/Datasheets/008-0309-0.pdf

Any ideas.

Thanks.

What frequency crystal are you planning to use?

If 32.768 kHz, use "Low Frequency" crystal oscillator.

If 8 MHz or 16 MHz (Arduino compatible) you can use either "Low Power" or "Full Swing". The Arduino uses "Low Power".

Sorry, yes, It will be a 8Mhz crystal. I don't believe I saw a low-power option in the fuse calculator I was using... Will selection the "wrong" option, low-power vs full-swing cause bad things to happen?

Thank you!

RobDrizzle:
Sorry, yes, It will be a 8Mhz crystal. I don’t believe I saw a low-power option in the fuse calculator I was using… Will selection the “wrong” option, low-power vs full-swing cause bad things to happen?

The “Low Power” setting saves power. It is more prone to electrical interference but every Arduino uses that setting so I would recommend it.

hmmmm... Using this fuse calculator with the atmega 328p selected, I do not seem to get that option.

http://www.engbedded.com/fusecalc/

If I have time tonight, I'll read through the data sheet to see whats going on.

RobDrizzle:
hmmmm... Using this fuse calculator with the atmega 328p selected, I do not seem to get that option.

AVR® Fuse Calculator – The Engbedded Blog

If I have time tonight, I'll read through the data sheet to see whats going on.

Apparently "Low Power Crystal Oscillator" is so standard they just call it "Ext. Crystal Osc.". You can tell because of the CKSEL ranges in the datasheet:

Low Frequency Crystal Oscillator = 0100 through 0101
Full Swing Crystal Oscillator = 0110 through 0111
Low Power Crystal Oscillator = 1000 through 1111

John,
Thank you. You're a mountain of information.