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Topic: Standalone ATMega328 Crystal Selection (Read 2 times) previous topic - next topic

smeezekitty

I would personally just use a resonator. They are cheap and the frequency inaccuracy is generally mostly FUD.
The worst case error on a resonator is usually around 0.7%, usually much better.
This is a difference of 112KHz (usually less) which is reasonable. The internal RC oscillator is generally much worse then this.

Also claiming that it would be a problem with serial communication is also totally false since it would need to be atleast 5% off to affect it.
Avoid throwing electronics out as you or someone else might need them for parts or use.
Solid state rectifiers are the only REAL rectifiers.
Resistors for LEDS!

Coding Badly

The worst case error on a resonator is usually around 0.7%, usually much better.


Not that it matters much for this discussion but the resonator on my UNO is almost 2% too slow.  I can actually tune the internal oscillator to be more accurate (just less than 0.2%).

tim7


I would personally just use a resonator. They are cheap and the frequency inaccuracy is generally mostly FUD.


A little while ago I made some measurements of frequency error and stability, comparing a resonator and a crystal.  The results are here:
http://arduino.cc/forum/index.php/topic,69316.msg516645.html#msg516645

Whether these errors are important depends on your application.

smeezekitty


The worst case error on a resonator is usually around 0.7%, usually much better.


Not that it matters much for this discussion but the resonator on my UNO is almost 2% too slow.  I can actually tune the internal oscillator to be more accurate (just less than 0.2%).

Strange... Maybe they should consider getting a better resonator. The parts I found on digikey were spec'd between 0.5% and 1% maximum error.

0.7% should allow for a change of 7000 PPM. Although this is quite a bit, it really only matters for precise timing applications of frequency generation.
Avoid throwing electronics out as you or someone else might need them for parts or use.
Solid state rectifiers are the only REAL rectifiers.
Resistors for LEDS!

westfw

Quote
the resonator on my UNO is almost 2% too slow.

That should be way out of spec.  I read typical datasheets as 0.5% nominal inaccuracy, plus up to 0.2% over the temperature range...

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