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Topic: Annotated board pictures (Read 1 time) previous topic - next topic

westfw

Some time ago I had put up the official Arduino Uno picture and added "photo notes" annotations describing (or at least labeling) most of the significant components on the board.  Yesterday I added an annotated MEGA2560 photo:

Uno: http://www.flickr.com/photos/58843278@N00/5402516093/
MEGA: http://www.flickr.com/photos/58843278@N00/5602080472/

Jack Christensen

Very cool!  Regarding the "could be" comments on the crystal and resonator, is that to imply that Arduinos may be manufactured with either?  All mine are as in your picture, crystal for the 8u2, resonator for the 328p.  I wonder why they chose to do it that way.  Being slightly OCD ;) I'd prefer crystals, although I certainly can't say I've done anything where it would make a practical difference.  Might be nice to know there's a little more accuracy for baud rate generation.
MCP79411/12 RTC ... "One Million Ohms" ATtiny kit ... available at http://www.tindie.com/stores/JChristensen/

djcrunkmix

This is fantastic. Thank you  XD

westfw

Quote
is that to imply that Arduinos may be manufactured with either?

Yes.  Both the crystal and resonator have some minor advantages over the other, but I don't know why they'd end up using one of each...

mowcius

#4
Apr 10, 2011, 03:38 pm Last Edit: Apr 10, 2011, 03:39 pm by mowcius Reason: 1
I think they now use a resonator for both.


The crystals in my mind are better but very large unless you go for the very expensive SMD ones.

I don't quite know what advantages the resonator has (apart from being cheaper).

Drmn4ea

From what I understand, resonators are less accurate, but tend to start-up / stabilize faster, which could matter in specific applications. They are often commonly manufactured with capacitors built-in; these are probably easier to "drop in" to a design and use (less fussing about finding the correctly-matching caps for the oscillator and guard rings / other layout issues). That's probably more of an issue for the very low power, low speed xtals, e.g. 32.768kHz watch crystals, but I have been bitten before by such crystals not starting up reliably using the manufacturer-recommended values, and having to stack on 1pf caps until they worked!

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