I have made several projects that include crystals/resonators. I have used them in clock circuits, microprocessor timing, and communication timing. I have always used the 2-pin clocks ever since the first Arduino I held in my hands. The two-pin crystal has been a mainstay in all of my layouts.
Until today, I was looking at the below schematic thinking it was just a fancy footprint of two capacitors and a crystal.
I remember looking at small aftermarket Pro Mini's and Nano's thinking they left the capacitors off of their clocks and tossed them aside thinking they were just cheap clones.
And if the real estate on your circuit board is really busy, you can also get a transistor inside that can which will complete the entire oscillator in a single crystal can. Another pin on the bottom, of course.
Be aware that many of the self-contained "Cystal oscillators" are significantly "power hungry", often consuming more current than the AVR CPU (20mA+) (and they don't get turned off by the power-saving modes.)
All true! I remember one batch of those devices generated a spur that killed the GPS receiver that it was part of. Customer about went crazy when the devices were returned from customers. Took him weeks to find the problem. But the gracious vendor sent a new batch number and took all the bad ones back. Stuff happens!
Yes, that was my point. Arduino mostly use a 2-pin resonator/crystal/oscillator with the caps external. The Arduino Nano uses a 3-pin version with the capacitors packaged inside the can.
