R3 is the latest release of an easy-to-use open source controller, hardware and compared to no major changes, the biggest difference is that USB to serial circuit part, switch to an ATMega16U2 microcontroller, which also increased the cost of the software part of the same as before, no major changes.

Features:

1. Pin changes: two additional I2C pins (SDA and SCL, only Analog 4 and 5 copy, not an additional I2C interface) next to the AREF pin, plus two pins next to RESET, one for IOREF , So that the expansion board to adapt to the onboard voltage, the pin is only to tell the expansion board is currently the number of onboard voltage (such as is 5V, can be seen as the power pin copy, does not provide level pull), the other is the future Standby pin used.

2. More stable RESET circuit. RESET key position has changed, was moved to the USB interface near the corner, more convenient to press.

3. ATmega16U2 instead of 8U2, this does not mean that 16K flash R3 can make your code run faster, this update is a USB interface chip services, in theory, it allows to simulate USB HID, such as MIDI / Joystick / Keyboard.