The “LeoStick” has to win the prize for the cutest microcontroller development platform.
It’s (mostly) compatible with the Arduino system and plugs straight into a USB port – no cable or connector required. Normally it’s powered from the USB but a separate power supply can be used if desired.
It’s slightly thicker than a typical PCB and has gold-coated pads on a small projection, arranged in the right layout to make contact with the four USB pins.
Like other Arduinos, this one features an 8-bit Atmel AVR microcontroller. In this case it’s an ATmega32U4 which has built-in USB support. That makes this a much neater (and smaller!) solution than the majority of Arduino boards which tend to use separate USB-to-serial chips.
On board are two RGB LEDs, one for power/USB activity and the other for the user software to control. There’s also a tiny reset button, a piezo buzzer and a row of pads on either side to accept socket strips, pin headers or wires. The pads include 14 digital I/Os (seven of which can be PWM outputs) and six analog inputs which can also be used as digital I/Os.
There are also pads to access the power supply and other pins, including the ADC reference voltage. Note that four of the digital I/Os are shared with the user LED and piezo buzzer.
One option for adding circuitry to the LeoStick is to purchase a Freetronics ProtoStick pack which gives you a PCB with 14 x 4 holes of prototyping area and a couple of pin headers. This plugs right into the LeoStick once you’ve fitted the provided socket strips to it.