TwoWire

Twowire, usually written as TwoWire or referred to as the two-wire interface, denotes the two-wire serial communication widely used as I2C. The term encompasses both the hardware peripheral that implements the I2C/TWI protocol and the software abstractions that control it on microcontrollers. The two wires, SDA (data) and SCL (clock), carry the communication, with devices addressed on the bus.

In hardware terms, many microcontrollers include a dedicated Two-Wire Interface (TWI) peripheral that supports I2C-compatible master and, on some devices, slave operation. In software, a library or class named TwoWire (commonly exposed as Wire on many platforms) provides a higher-level API for initializing the bus, configuring pins and clock speed, and performing data transfers. The software layer aims to simplify start and stop conditions, addressing, data buffering, and error handling.

Typical operations involve initializing the bus with a begin function, starting a transmission to a device with beginTransmission, sending data with write, and completing the transfer with endTransmission. Reading from a device uses requestFrom to retrieve data, followed by read and available to access it. Some platforms also expose slave-mode capabilities through onReceive and onRequest handlers. Frequency settings commonly range from standard (around 100 kHz) to fast (400 kHz) and beyond, depending on hardware support.

Multi-bus support is common on more capable microcontrollers; boards such as ESP32 expose multiple TwoWire instances (for example, separate Wire objects) to operate more than one I2C bus simultaneously.

See also: I2C, TWI, I2C bus, Wire library.