IOIO (pronounced yo-yo) is a series of open source PIC microcontroller-based boards that allow Android mobile applications to interact with external electronics.^[2][3][4] The device was invented by Ytai Ben-Tsvi in 2011, and was first manufactured by SparkFun Electronics.^[2][5][6][7] The name "IOIO" is inspired by the function of the device, which enables applications to receive external input ("I") and produce external output ("O").^[4]

The IOIO board contains a single PIC MCU that acts as a USB host/USB slave and communicates with an Android app running on a connected Android device.^[8] The board provides connectivity via USB, USB-OTG or Bluetooth, and is controllable from within an Android application using the Java API.^{[1][4][9][10][11]}

In addition to basic digital input/output and analog input, the IOIO library also handles PWM, I2C, SPI, UART, Input capture, Capacitive sensing and advanced motor control.^[3] To connect to older Android devices that use USB 2.0 in slave mode, newer IOIO models use USB On-The-Go to act as a host for such devices.^[1] Some models also support the Google Open Accessory USB protocol.^[4]

The IOIO motor control API can drive up to 9 motors and any number of binary actuators in synchronization and cycle-accurate precision.^[12][13] Developers may send a sequence of high-level commands to the IOIO, which performs the low-level waveform generation on-chip.^[12][13] The IOIO firmware supports 3 different kinds of motors; stepper motors, DC motors and servo motors.^[12][13]

Device firmware may be updated on-site by the user.^[3] For first-generation devices updating is performed using an Android device and the IOIO Manager application available on Google Play.^[3][14] Second-generation IOIO-OTG devices must be updated using a desktop computer running the IOIODude application.^[15]

The IOIO supports both computers and Android devices as first-class hosts, and provides the exact API on both types of devices.^[3] First-generation devices can only communicate with PCs over Bluetooth, while IOIO-OTG devices can use either Bluetooth or USB.^[3] PC applications may use APIs for Java or C# to communicate with the board; Java being the official API.^[11][16]

The IOIO hardware and software is entirely open source,^[17] and enabled the creation of hundreds of DIY robotic projects around the world.^{[18][19][20][21][22]}

The board has been featured in various learning kits, which aim to help students write Android applications that can interact with the external world.^{[3][23][24][25]}

The Qualcomm Snapdragon Micro Rover is a 3D printed robot that leverages an Android smartphone and the IOIO to control the robot's motors and sensors.^[26][27] A team led by Israeli inventor Dr. Guy Hoffman created an emotionally-sensitive robot, that relies on the IOIO to control the robot's hardware.^[28]

The IOIO has been variously described as a "geek's paradise", "an easy way to get I/O from an Android device’s USB connection" and "a USB I/O breakout board for Android smartphones which turns your handset into a super-Arduino of sorts".^{[18][29][30][31]} It featured as a recommended "gift for geeks" in a Scientific Computing article.^[25]

According to SlashGear, an online electronics magazine:

You could hook up the IOIO for Android and a couple of heat sensors, and whip up an app that measures room temperature and then emails you if it’s getting too hot. Thanks to a range of I/O choices – including Digital Input/Output, PWM, Analog Input, I2C, SPI and UART control – you could also connect your home thermostat to automatically adjust the heating in response.

— Chris Davies, "IOIO for Android gets video demos: Geek’s paradise!", SlashGear^[18][32]

According to SparkFun, the first manufacturer of the device:

You can combine the awesome computing power, Internet/Bluetooth connectivity, touch screen, and a variety of sensors from your Android device with the ability to easily add peripheral devices to interact with the outside world. Also, using the IOIO does not require any hardware or software modifications to your Android device, thus preserving the warranty as well as making the functionality available to non-hackers.

— Publishing Team, "IOIO Android Interface Board Retail", SparkFun^[8][32]

According to Ytai Ben-Tsvi, the inventor of the device:

Android phones are powerful mobile computers having internet connectivity and a rich variety of built-in sensors (camera, GPS, IMU, touch screen). They are also very easy to write applications for, thanks to the great work done by the Android SDK developers. For many applications, all they are really missing is connectivity to external peripherals. This is exactly where IOIO fits in: it enriches the inherent capabilities of the Android device with the ability to communicate with external circuits.

— Ytai Ben-Tsvi, "Meet IOIO - I/O for Android"^[33]

• Arduino
• BeagleBoard
• Raspberry Pi
• PICkit
• Open-source robotics
• PIC microcontroller