Can anyone point me to the datasheet or user manual for the Elegro Uno R3? If not that, the same documents for the Arduino Uno R3 may do. The only thing I can find so far is the pinout for the Arduino Uno R3 board.
It seems these documents should be easy to locate. But I sure can't find them.
I think that this is a very precise description. If a board does not implement what the R3 revision specifies then it can not be named "Uno R3".
AFAIK the Uno R3 layout (files...) is freely usable. I got boards from China which even did not change the "Made in Italy" label.
DrDiettrich, Thank you for taking the time to respond. But as far as I can tell, your response contained nothing which answered my question in any way.
1522237550_arduino uno r3.pdf (4art-studio.com)
Any board marked Uno R3 will follow these specs.
The pin layouts will be identical.
What specific information are you looking for?
Navigate to the product page of the Arduino Uno R3: Arduino Uno Rev3 — Arduino Official Store.
Scroll down to
The meaning of "R3" in the context of the official Arduino Uno is explained on the product page:
https://store.arduino.cc/products/arduino-uno-rev3/
Revisions
Revision 3 of the board has the following new features:
- 1.0 pinout: added SDA and SCL pins that are near to the AREF pin and two other new pins placed near to the RESET pin, the IOREF that allow the shields to adapt to the voltage provided from the board. In future, shields will be compatible with both the board that uses the AVR, which operates with 5V and with the Arduino Due that operates with 3.3V. The second one is a not connected pin, that is reserved for future purposes.
- Stronger RESET circuit.
- Atmega 16U2 replace the 8U2.
But when you see "R3" or "Rev3" mentioned in the context of accessory products or derivative boards, what they actually mean is "1.0 pinout". It is about the presence of the SDA, SCL, and IOREF pins, which the previous pinout version did not have. You can find Uno derivatives advertised as "R3" even though they use the CH340 USB chip in place of the ATmega16U2, as well as other miscellaneous hardware adjustments.
Arduino even does it:
That shield is in no way dependent on whether there is an ATmega16U2 on the carrier board, nor on the components in the carrier board's reset circuit. By "Rev3", they just mean that it has SDA, SCL, and IOREF pins.
It's important to take note of whether your board has the 1.0 pinout because some shields use the added pins, and so won't work on a board that doesn't have the 1.0 pinout.
Prior to the addition of the SDA and SCL pins, shields that used I2C communication would make the I2C bus connections on pins A4 and A5, which also provide I2C bus connection on the Uno. However, the I2C bus pins are in different locations on other boards (e.g., Mega, Leonardo, Due). So this meant that those shields could not be used on any board, or perhaps you had to configure the shield for your board via some solder jumpers. So this "1.0 pinout" was really an important advancement for the Arduino shield ecosystem.
groundFungus Thanks for the main processor datasheet.
er_name_not_found Thanks for the document which has some of the type of info that I might need.
To those asking what exactly do I need: I don't know. I've been an electrical engineer for over 40 years. Typically a board like this will have good technical documentation to cover all of its technical details. Operating temperatures, power consumption, I/O pin current/voltage threshold characteristics and timing requirements, and a million other things. For instance, last night I was wanting to know how much current can the board's +5V pin safely supply to the outside world. Who knows what I'll want to know next week? Usually this type of info is readily available for a board so widely used. I'm seeing that bits and pieces of this type of info are available by going to a variety of sources - datasheets for chips on the board, schematics, pinout documents, etc. But it would be good, and typical, for the collection of this type of info to be aggregated together into a single, large, useful document.
That's the controller data sheet that covers almost everything.
Understanding the remaining power supply components around the controller should not be a problem for an electrical engineer 
Unfortunately there is way too little documentation on that, other than you should not use it to power anything that needs any significant amount of current. When powered from USB, there is a 550mA polyfuse to protect the USB port, but when powered from the barrel connector the current is limited by the heat dissipation of the on-board regulator. The barrel connector is considered by some on here to be little more than a decorative item, that should not be used to power anything external to the UNO itself.
Anything that needs significant current should be powered from an external 5 volt regulator.
I don't believe you. The Arduino is not an electronics component; it's an educational tools, more like a vendor's "evaluation board" than something designed to be incorporated into a product. If you look at something like a Microchip "Curiosity" board, NXP "Freedom" board, or an ST "Discovery" or "Nucleo" board, their documentation is only slightly better than the Arduino documentation, and "refer to individual chip documentation for further details."
That said, the Arduino documentation is not very good, and the "clone" vendors frequently have no documentation at all (beyond "it's like an uno r3, with a different serial/usb chip.") 
(and, MOST of the Arduino boards aren't much more than a breakout board for whatever processor they use, so there really isn't that much to document beyond what is in the processor chip data sheet.)
At this point, I believe we're dealing with opinions of what level of document should be available. I hope you can agree that we can each have our own differing opinions on this. Thank you for your comments.
They have just recently started producing more formal datasheets for the official Arduino boards. They are on the hardware documentation pages linked from here:
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