I2C or Inter-Integrated Circuit is a widely-used communication protocol that allows multiple devices to communicate with each other using just two wires. It is extensively used in various electronic applications such as microcontrollers, sensors, and displays. In this article, we will see some most commonly asked “I2C Interview Questions along with their Answers”.

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Most commonly asked “I2C Interview Questions”

If you are preparing for an I2C interview, you must be well-versed in the concepts and must have a clear understanding of the protocol. In this article, we will provide you with some of the most commonly asked I2C interview questions along with their answers.

Q1) What is I2C, and how does it work?

I2C is a serial communication protocol that allows multiple devices to communicate with each other using just two wires, namely, SDA (Serial Data) and SCL (Serial Clock). It works on a master-slave architecture, where the master device initiates the communication and the slave device responds to it.

Q2) What are the advantages of using I2C?

The advantages of using I2C are:

It requires only two wires for communication, which makes it simple and cost-effective.
It allows multiple devices to communicate on the same bus, which reduces the number of wires required.
It supports multiple master devices on the same bus, which increases the system’s flexibility.

Q3) What is the maximum speed supported by I2C?

The maximum speed supported by I2C depends on the mode of operation. The standard mode supports a maximum speed of 100 Kbps, while the fast mode supports a maximum speed of 400 Kbps. The high-speed mode and ultra-fast mode support a maximum speed of 3.4 Mbps and 5 Mbps, respectively.

Q4) What is the difference between I2C and SPI?

The main difference between I2C and SPI is the number of wires required for communication. While I2C requires only two wires (SDA and SCL), SPI requires at least four wires (MOSI, MISO, SCK, and CS). Additionally, I2C uses a master-slave architecture, whereas SPI uses a master-slave architecture or a peer-to-peer architecture.

Q5) How does a master device detect the presence of a slave device on the I2C bus?

The master device detects the presence of a slave device on the I2C bus by sending a START condition followed by the slave address. If the slave device is present on the bus, it will respond with an ACK (acknowledge) signal. If the slave device is not present on the bus, it will not respond, and the master device will generate a NACK (not acknowledge) signal.

Q6) What is a repeated start condition in I2C?

A repeated start condition in I2C is when the master device generates a START condition on the bus without first generating a STOP condition. This allows the master device to continue communicating with the same slave device without releasing the bus.

Q7) What is clock stretching in I2C, and how does it work?

Clock stretching in I2C is a mechanism where a slave device can hold the SCL line low to slow down the clock speed. This thing is giving it more time to process data. The master device will wait until the SCL line is released by the slave device before continuing with the communication.

Q8) What is arbitration in I2C, and how is it resolved?

Arbitration in I2C is a mechanism used to resolve conflicts when multiple master devices try to access the same slave device simultaneously. When a conflict occurs, the master devices continue to transmit data until they detect a different value on the SDA line. The device that detects the different value will lose the arbitration and stop transmitting data, allowing the other device to continue with the communication.

Q9) What is the difference between a 7-bit and 10-bit I2C address?

I2C supports two types of addressing modes: 7-bit and 10-bit addressing. In 7-bit addressing, the address field consists of 7 bits, allowing for up to 128 slave devices on the bus. In 10-bit addressing, the address field consists of 10 bits, allowing for up to 1024 slave devices on the bus. However, 10-bit addressing is less commonly used due to its higher complexity.

Q10) What is a multi-master I2C configuration, and how does it work?

In a multi-master I2C configuration, multiple master devices are connected to the same bus, allowing them to communicate with the same set of slave devices. Each master device can initiate communication on the bus, and conflicts are resolved using the arbitration mechanism. However, it requires careful management to avoid conflicts and ensure that each device can complete its transactions.

Q11) What is clock synchronization in I2C, and why is it important?

Clock synchronization in I2C refers to the process of ensuring that all devices on the bus are operating at the same clock speed. This is important to ensure reliable communication and prevent data corruption. If the clock speeds of different devices are not synchronized, it can lead to timing issues and data errors.

Q12) What is the role of pull-up resistors in I2C, and why are they necessary?

Pull-up resistors are used in I2C to ensure that the SDA and SCL lines are held at a high voltage level when no device is driving them. This is necessary to prevent the lines from floating and potentially causing errors in communication. The value of the pull-up resistors must be chosen carefully to ensure that the rise and fall times of the signals are within the specifications of the devices on the bus.

Q13) What is the difference between I2C and SMBus?

SMBus (System Management Bus) is a subset of the I2C protocol that adds additional features such as device discovery, error checking, and battery charging control. It is designed for use in systems management applications such as desktop and mobile computers. However, it is fully backward compatible with I2C devices, and most I2C devices can be used on an SMBus.

Q14) What is the role of clock stretching in I2C, and why is it necessary?

Clock stretching is an important feature of I2C that allows slave devices to slow down the clock speed when they are not ready to receive data. This is necessary to prevent data loss and corruption and to ensure that all devices on the bus have sufficient time to process data. Without clock stretching, it would be difficult to ensure reliable communication in systems with slow or busy devices.

Q15) How does I2C support the hot plugging of devices?

Hot-plugging refers to the ability to add or remove devices from a system while it is running. I2C supports hot-plugging by allowing devices to be added or removed from the bus without disrupting communication with other devices. When a new device is added to the bus, it is assigned a unique address. And it can begin communicating with other devices immediately.

Q16) What is the maximum data rate supported by I2C?

The maximum data rate supported by I2C depends on the specific implementation and the devices on the bus. The standard mode supports a maximum data rate of 100 kbps, while the fast mode supports up to 400 kbps. The high-speed mode supports up to 3.4 Mbps, and the ultra-fast mode supports up to 5 Mbps.

Q17) How does I2C ensure reliable communication in noisy environments?

I2C uses several mechanisms to ensure reliable communication in noisy environments. One of these is the use of pull-up resistors, which help to filter out noise and prevent the lines from floating. Another mechanism is clock stretching, which allows slave devices to slow down the clock speed when they are not ready to receive data. Additionally, devices may implement error-checking mechanisms to detect and correct errors in data transmission.

Q18) How does I2C differ from SPI?

SPI (Serial Peripheral Interface) is another serial communication protocol that is commonly used in embedded systems. While both I2C and SPI are used for communication between microcontrollers and peripherals, they differ in several ways. For example, SPI uses separate lines for data and clock, while I2C uses a single bidirectional data line. Additionally, SPI typically supports higher data rates than I2C but is less suited for communicating with large numbers of devices. Also, the difference between I2C and SPI is given in the article “I2C Vs SPI“.

Q19) What are some common applications of I2C?

I2C is widely used in various applications such as embedded systems, consumer electronics, and industrial control systems. In particular, it is commonly used for communication between microcontrollers and sensors. Microcontroller or other peripherals, as well as for controlling LCDs and enabling communication between audio codecs and digital signal processors.

Q20) How can I test an I2C bus to ensure that it is functioning correctly?

To test an I2C bus, you can use a logic analyzer or an oscilloscope to monitor the SDA and SCL lines and ensure that the signals are within the specified voltage levels and timing parameters. You can also use a device such as a bus analyzer to capture and analyze I2C traffic on the bus. You can use software tools I2C bus scanners to scan the bus for connected devices and verify their addresses.

I2C is a widely used communication protocol between microcontrollers and peripherals. It offers benefits like hot plugging, noise tolerance, and support for multiple devices. Understanding addressing, clock sync, pull-up resistors, clock stretching, and error checking is important for proper implementation and troubleshooting. With this knowledge, engineers and developers can effectively design and implement I2C-based systems for many applications.