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April 17, 2024

I2C vs. SPI: Selecting the Right Interface for Your Project


In electronic systems, communication plays a vital role. It governs how the electronic devices exchange data with each other. Communication protocols are like the machine learning language between the devices that understand each other’s messages. These protocols define the timing, format, sequence, and error checking of the data transmission. Electronic systems consist of various types of communication protocols to facilitate effective communication between devices.

This article provides a brief description of two major communication protocols; I2C and SPI, their differences, and the factors you have to consider for choosing the right interface for your project.

What is a Serial Peripheral Interface (SPI)?

SPI is a full-duplex serial communication protocol used in electronics. It consists of a single master device, like a microcontroller or microprocessor, and two or more slave devices, like sensors, GSM, and more. This communication interface is widely used in embedded systems for short-distance communications between the peripheral IC and microcontrollers. The various signal lines of the microcontroller connect to the SIP chip. It then ensures proper data communication with the peripheral IC.

It uses the four signal wires for communication interfaces. However, it doesn't include the lines for power and ground. The four active signal lines of SPI are as follows:

  • Slave Select (SS)
  • Master Out Slave In (MOSI)
  • Serial Clock (SCLK)
  • Master In Slave Out (MISO)

Application of SPI

The major applications of SPI are as follows:

  • SPI is commonly used in data storage devices like SD cards and flash memory chips.
  • SPI enables high-speed data transfer. Thus, it is used in networking devices, including Wi-Fi, Ethernet devices, Bluetooth receivers, video game controllers, etc.
  • SPI is used in sensor networks to connect several sensors to a central processing unit or microcontroller.
  • The high-speed data transfer makes SPI a suitable choice for video streaming, touchscreen, video game controllers, and more.
  • SPI is used in various sensor nodes, industrial automation, environmental monitoring systems, and more.

What is Inter-Integrated Circuit (I2C)?

I2C is a serial communication interface with multi-master devices and multiple slave devices. So, with the I2C bus, you can connect your master devices, like microcontrollers, to various slave devices, like sensors and more. In other words, you can say it’s a bus interface protocol primarily for serial communication. It provides robust and simple communication between the microcontroller and the peripheral IC or device.

The I2C bus is a two-wire communication interface. It helps to connect low-speed devices like I/O interfaces, converters like A/D and D/A, microcontrollers, and other peripheral ICs in embedded systems. The two wires, SDA and SCL, are the bidirectional serial communication lines. The SCL line carries the clock signal, while the SDA helps transceive the data between master and slave devices.

Application of I2C

The applications of the I2C communication protocol are:

  • I2C is used to read the hardware sensors and control the user-directed actions.

For example, you can see the I2C bus in smart home devices like lighting systems, thermostats, and automatic environmental sensors.

  • I2C can be found in communication between various controls, sensors, and models in vehicles. It includes applications like ADAS systems, climate control systems, and engine management systems in the automotive industry.
  • I2C is used in medical industries. It can be found in devices like patient monitoring systems, biomedical sensors, and more.

Comparing I2C and SPI


  • I2C is a simple communication protocol. I2C uses the two-wire system, which is an advantage in terms of simple wiring and minimal board space as compared to SPI. It makes it the preferred choice for many electronic projects.

I2C also supports multi-device communication on the same bus network. Thus, it helps with the easy integration of multiple peripheral ICs into a single system.

  • Whereas SPI is the full-duplex system that allows the simultaneous transmission of data. Besides, it also offers flexibility in configuration and supports multiple slave devices. It is suitable for high-speed data communication systems.


I2C is prone to signal degradation and noise. Thus, the performance of the I2C bus degrades over a longer distance, which could limit the range for your project.

SPI has the limitation of being a highly complex communication protocol as compared to I2C. It requires a four-wire system for effective communication. It increases the wiring complexity as well as the board space and designs.

Power Consumption

I2C operates at low speed, so it consumes less power as compared to SPI. It makes it suitable for projects where power efficiency is a major factor.

SPI consumes more power as compared to I2C. This is because SPI is used for high-speed data transmission. Thus, designers should carefully consider the power requirements while selecting the SPI for the projects in terms of low-power applications.


I2C supports communication protocols in the electronic industry, with many devices offering built-in I2C compatibility.

While the compatibility and interoperability of SPI depend on the specific implementation and considerations.

Choosing the Right Interface for Your Project

Data Transfer Requirement

Based on your project, try to check the speed and volume of data to be transferred. Protocols like SPI offer high-speed communication for transferring large amounts of data, while I2C is suitable for low-speed applications.

Environmental Factors and Distance

Consider the distance where communication is required. Also, the environmental conditions of the project should be considered.

Number of Devices

Determine the devices that need to transmit the data in your project. I2C and SPI support multiple device connections in the same peripheral network, while protocols like UART are for point-to-point communication.

System Resource Utilization

Consider the availability of system resources, such as GPIO pins and processing power, on your microcontroller or microprocessor. Some protocols may require more resources than others, so ensure compatibility with your hardware and allocate resources accordingly.


Plan for the future scaling and growth of your project by selecting a communication protocol that enables the simple integration of new devices or functions. Consider how easily you can add additional devices to the communication network without making significant changes to your current arrangement.


This article presents the two major communication protocols, I2C and SPI. Each protocol has its advantages and limitations. Thus, before selecting the one for your project, try to consider the above-listed points so that it align with your requirements.

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