I²C, pronounced “I-squared-C”, stands for Inter-Integrated Circuit. Invented by Philips (now NXP Semiconductors) in the early 1980s, it’s a bi-directional, two-wire (usually) serial communication protocol primarily used to link a microcontroller to peripheral devices or other microcontrollers. Understanding I²C (Inter-Integrated Circuit): How It Works The realm of embedded electronics often revolves around communication. Among the myriad of communication protocols available, I²C stands out due to its simplicity and efficiency. In this article, we’ll dive deep into the world of I²C, unraveling its intricate workings for those who want to master its use. The Basics: Master and Slave In the I²C world, there are two primary roles: Master: Initiates and controls the data transfer. Slave: Responds to the master. Each slave on the bus has a unique address. Multiple masters and slaves can be connected on the same bus, but only one master can take control at a time. The Two Wires: SDA and SCL The elegance of I²C is encapsulated by its two-wire system: SDA (Serial Data Line): Where the data is transmitted and received. SCL (Serial Clock Line): The clock signal generated by the master to synchronize data transfer. Start and Stop Conditions Communication in I²C begins with a start condition (a high-to-low transition on the SDA line while SCL remains high) and ends with a stop condition (a low-to-high transition on the SDA line while SCL remains high). Data Transfer and Acknowledgment After the start condition, the master sends the address of the targeted slave and a read/write bit. The addressed slave then sends an acknowledgment bit (ACK) to confirm receipt. Each byte of data is followed by an ACK bit. If a slave doesn’t acknowledge, it’s a sign of an issue in communication, and the master can opt to retry or abort the transaction. Clock Stretching One interesting feature of I²C is clock stretching. A slave can hold the SCL line low after receiving or sending a byte, signaling the master to wait. This mechanism ensures that a slower slave can keep up with a faster master. Advantages and Limitations Advantages: Simple hardware interface. Supports multiple masters and slaves. Built-in error checking with ACK/NACK. Lower pin count compared to parallel interfaces. Limitations: Slower data rate compared to SPI. Address conflicts if two slaves have the same address. Limited to short-distance communication. Conclusion I²C is a robust and efficient communication protocol that has found its way into numerous applications, from simple sensors to complex systems. Its simplicity and the capability to address multiple devices with just two wires make it a go-to choice for many designers. While it has its limitations, understanding its intricacies ensures that one can leverage its strengths to the fullest.