I²C bus, also called TWI is a popular electronic bus designed for low-speed communication between different peripherals. As an MLAB's component it is mostly used to ensure communication between microprocessor and sensors. I²C derivative SMUus differs from it in that it contains timeouts' definitions and Packet Error Checking and therefor is, in sense, more robust than the original I²C.

Thanks to an advancement in computer technologies new possibilities arise allowing the use of the bus for direct communication between sensors and Linux systems. Furthermore, with the help of I²C adapter the bus can be connected to PC as well.

Although the I²C bus was originally designed to link devices on small scales (within the dimensions of PCB), using certain techniques it is possible to enlarge its range to tens of meters ¹⁾. However, it must be noted that such approach may not be safe because over long wires a high voltage can be electrostaticilly and electormagnetically induced and can cause damage to connected devices. The exact distance over which it is safe to use the I²C bus depends on the surrounding environment and the required reliability of the system.

Linking of I²C devices within MLAB is implemented on several levels according to extent of a network. Locally (on scale of several meters), the modules are connected by MLAB cables and separated by i2chub. This module also solves the conversion between logic 3.3V and +5V.

Over more extensive distances the bus is linked through shielded signal cables ending in female connectors and connected to uniserial module. This module also contains a basic surge protection and most importantly acts as a mechanical bridge between 'heavy external wiring' and fine internal linking of devices.