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Arduino Leonardo ATmega32u4 with headers - in stock!

The latest addition to the Arduino family is here! The Arduino Leonardo is a microcontroller board based on the exciting USB-enabled ATmega32u4 (datasheet). This chip has about the same amount of flash, RAM and capability as the ATmega328 found in the UNO. It has 20 digital input/output pins (of which 7 can be used as PWM outputs and 12 as analog inputs), a 16 MHz crystal oscillator, a micro USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started.

The Leonardo differs from all preceding boards in that the ATmega32u4 has built-in USB communication, eliminating the need for a secondary chip (such as an FTDI friend, FTDI cable or the USB/Serial converter on the UNO). On one hand this means that sketches on the Leo are a little bigger because it's also handling USB interaction. On the other hand, it allows the Leonardo to appear to a connected computer as a mouse and/or keyboard, in addition to a virtual (CDC) serial / COM port. It also has other implications for the behavior of the board; these are detailed on the getting started page.

We're very excited to have a small shipment of Leo's in stock. Please note that this board is very new and so is best used by people with existing Arduino experience as there may be a bug that trips up beginners. It is probably not going to work with nearly any shields other than the proto shield. We haven't gone through and tested it with all the Adafruit shields and don't guarantee it will work until we've sat down and done a lot of testing and coding, so keep that in mind!

This board is only supported in the latest Arduino IDE 1.0.1 so you will also need to update the IDE.
Ethan Dicks's profile photoDoug Smith's profile photoIvo Noorhoff's profile photoAndrew Meier's profile photo
So, this is like an arduino MEGA in an uno footprint?
cool ....would love to try asap
Before everyone gets too excited, make sure to read the fine print on the Adafruit product page: "It is probably not going to work with nearly any shields other than the proto shield."
So, be careful, you might not be able to leverage any investment you made in other shields, etc...
+Eric Bazerghi I saw that & I don't use any shields currently, but still wondered why this is the case?
The I/O pin labelling is superficially the same, but there are functional differences between the ATmega32u4 and the ATmega328. I can't possibly meaningfully summarize the differences, especially with so much information on the "Getting Started" page.

I ordered one because I want to play with some of the new flexibility in terms of different USB kinds of USB devices the Leonardo can show up as (Mouse, Keyboard, etc). I do have a few shields (Video Experimenter, Danger, DF-Robot LCD and buttons...) and will probably see which ones work and which ones do not. I think the Danger Shield might have a problem with changed SPI functionality, for example.
I already have a 32u4 board that isn't pin2pin compatible with Arduino shields. As a matter of fact, I have two - Teensy ( and Adafruit4 ( With LUFA (, you can program USB mice, keyboards, joysticks, serial ports, etc... for months now (and there's Teenyduino, but I've not used it). Also, I'm concerned what this can do to the existing shield environment ('Oh, you wanted a "Uno" version of the shield, we only have a "Leonardo" version'). I'll keep an eye on these, but I still don't see a reason to order one, especially anytime soon.
Finally, the reset button is located so you can reach it, even with a shield on! :D
Nobody said anything about the Uno, what with the '16U2 alongside the '328.. That was a stepping stone to this. Cost reduction.
Nothing against the Teensy - that's an interesting board all by itself, but the Leonardo is mostly Uno-shield-compatible - the cautions raised are just so that the hasty buyer doesn't have unreasonable expectations that random shield Foo is guaranteed to work. Because the processor is from a new family, some things have moved. Some shields will work, some will not, and of the ones that don't work right away, with a bit of work, possibly some hardware mods (trace cuts and jumps or external connections) could make them work.

We already have this situation to a small extent with Uno vs Mega.

I certainly hope that we don't start seeing "Leonardo Only" shields, but I can envision shields that might need a jumper or two moved for Uno vs Leonardo.
Because of the pin issues, I wish they would have taken advantage of this to make the Leonardo the next generation of Arduino. Utilize all those pins and couple it with Arduino's famous beginner-friendly nature. I'm interested in the Leonardo, but I think the Teensy fills the hole just fine (though I look forward to the Open source Leonardo files turning into something breadboard compatible.
+andrew  This particular component is far too underpowered to do anything along the lines of a tablet, at least not one in the Ubuntu range. However, you could use a Leonardo to build a very simple tablet-like microcomputer. You could add a touch screen, and presumably give it a couple of features - It wouldn't be able to surf the web, but you might be able to read a text file on it - ebook like functionality.  
There's a cool kickstarter project called Makey Makey that lets you interface all kinds of creative things to a PC through the USB port. This Arduino would really bring that project to the next level.
@Andrew- the ATmega32u4 is an 8-bit microcontroller with 32K of program memory (that is not possible to externally expand - look up the difference between Harvard Architecture and Von Neumann Machines) and 2.5K of internal RAM. It is possible to attach a variety of LCD panels to it, but not large ones unless they contain their own intelligent controller and more importantly, local RAM. I think you can get a 640x200 monochrome one that fits the bill for under $100. You aren't going to run Linux on this - the Raspberry Pi (same cost as a Leonardo) sounds more like the class of processor you are looking for.
Now if you could get this atmega in a DIP package or a ft232rl (could have that part # off) in a DIP then I would be psyched, but until then... its so much more affordable to prototype on a uno and use a atmega328p-pu and an FTDI USB cable, cause for a one-off project I'm not going to print a PCB and use SMT components.
+Ethan Dicks Thanks, they didn't have this page up the last time I was looking @ the Leonardo. I'm still very much a MC newb. so every little piece of info helps, generally just pointing the way is enough for me. Thanks, & cheers.
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