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Topic: Arduino Uno Rev3 pinouts photo (Read 94 times) previous topic - next topic


Dumb question... Did they change the USB interface chip and, why does its firmware need to be upgraded?

Nick Gammon

The older Uno had an Atmega8U2-MU USB interface. The Rev 3 Uno has an Atmega16U2-MU chip.

I presume the ability to upgrade the firmware is to allow for if it turns out to have some sort of bug, or maybe just for future expansion.


Here is a small part of the info from this link: http://www.ladyada.net/library/arduino/unofaq.html

  The USB controller chip has moved from an atmega8u2 (8K flash) to an atmega16u2 (16K flash). This does not mean that you have more flash or RAM for your sketches this upgrade is for the USB interface chip only. In theory this will mean that it will be easier to have low level USB interfaces such as MIDI/Joystick/Keyboard available. However these are only theoretical at this time, there is no example code or firmware which will actually do this.


Nick,  you didn't mention the extra pins on the power header. I think one has no connection the other is +5v also, tho not labelled that on the card.
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Nick Gammon

True, not on the photo. I mention the IOREF pin on the page I linked to.


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