The good folks at element14 sent me a set of the new Arduino Uno R4 boards to play with, and today I finally had some time to try them out (hooray for the rainy day!).
When you first power up the R4 WiFi, it does a neat little startup animation on the LED matrix, sort of Tetris-like, and then shows a heart. Very nice 
So then, of course, the first thing I do when I get a new board is to run the Blink sketch. This is a very small basic sketch that lets me know that things are working properly.
However, for some reason I could not get the LED to respond properly! The heart animation was gone, but the LED marked L1, that the pinout says is LED_BUILTIN, was doing a slow rhythmic fade-in/fade-out thing instead of blinking. I tried a few different blink speeds, with no luck.
I then tried the Minima, and it was fine - same LED location, so I assume it's the right one on the WiFi version.
I eventually noticed that I could get it to blink properly by hitting the reset button on the board.
Very odd. Not sure if that's a bug that still needs to be worked out, or if reset is a required thing now?
That's definitely different than the behaviour of the Uno R3, but then again, all of that WiFi stuff and LED matrix is too! Maybe the Minima is the one to use if you want to be sure of full backward compatibility.
I did also notice that the datasheet on the Arduino website says the LED in question is DL4 and is "LED SCK (serial clock)" (top of page 9).
So I guess there's some interference that's happening.
Anyhow, very cool new boards. I love the WiFi and LED matrix - I have a few ideas that I'll step through for the next phase of my adventures.
