The Olimexino-32U4 is based on the Arduino Leonardo, featuring an AVR ATmega32U4 microcontroller. The ATmega is pre-programmed with the Arduino bootloader that allows you to upload code to it via USB using the open-source Arduino development environment.

The ATmega32U4 has built-in USB communication, eliminating the need for a secondary processor. This allows the board to appear to a connected computer as a mouse and keyboard in addition to a virtual (CDC) serial / COM port. It also has other implications for the behavior of the board — particularly reset behavior compared to earlier Arduino boards. It also means that there are now separate Serial and Serial1 classes for the virtual serial driver and the hardware serial port, respectively. This also has an effect on the capabilities and assignments of some pins, e.g. SPI and TWI.

The ATmega32U4 allows for serial (CDC) communication over USB and appears as a virtual com port to software on the computer. The chip also acts as a full-speed USB 2.0 device, using standard USB COM drivers. It requires no drivers to be installed for Linux or Mac (for Windows a .inf file is included with the Arduino IDE software).

The main differences between this board and the official Leonardo are a mini-USB connector instead of micro-USB, a battery connector in addition to the power jack, a UEXT connector for additional peripherals, a 3.3V/5V selection jumper, and through-hole header pads at 0.1" pin spacing in addition to female headers at the traditional Arduino offset. The Arduino Shield connectors are a hybrid of R2 and R3 configurations. They have the added SDA and SCL pins of R3 on one side, but do not have R3's IOREF and unused pin on the other. The power selection jumper duplicates the job of the IOREF pin, only it is a manual setting rather than automatic.

Arduino Leonardo Compatible Board Features

• ATmega32U4 microcontroller, all-in-one USB communication; no need for external FTDI chip
• Input power supply 7-12V DC
• Ultra-low-power voltage regulators; consumption is only few microamps, which enables handheld and battery-powered applications
• Li-Ion rechargable battery power supply option with built-in on-board charger, so when you attach battery it is charged automatically and kept in this state until the other power source (USB or external adapter) is removed, then it automatically will power the board — no jumpers, no switches
• Works both on 3.3V and on 5V which is selectable with jumper, so 3.3V and 5V shields can be used
• UEXT connector (see below)
• Allows Real-Time Clock
• Noise-immune design
• The LEDs and the buttons are on the edge of the board so there is easy access even if a shield is plugged in
• All components are lower than the connectors, so the shields do not interfere with them
• mini-USB connector
• 0.1" spaced pin header pads (in addition to standard Arduino offset female headers) so you can use perforated boards to make your own shield
• All signals on the connectors are printed on top and on bottom of the board, so when you check a with probe you know exactly which port you are measuring
• 4 mounting holes make board attachment easier

UEXT Connector

Arduino Leonardo Compatible Board Resources

• OLIMEXINO-32U4 User Manual and Schematic
• OLIMEXINO-32U4 Design Files for Eagle
• Arduino documentation and software downloads
• Differences between Leonardo and other Arduino types
• Updated Bootloader Firmware allows an early-production OLIMEXINO-32U4 board to work under Arduino IDE 1.0.1 and above — AVR programming hardware will be required
• Drivers for Arduino 1.0.1 (shouldn't be necessary to download these as they should be installed with the IDE in a drivers folder)
• LED blink, Keyboard and Mouse Examples for Arduino IDE 1.0.0
• Simple Double LED Blink Demo for Arduino IDE 1.0.1
• Button Definition Example Code for Arduino 1.0.3
• SD/MMC Card Example Code for use with MOD-SDMMC