There is a lot of serial communication protocol but in which I2C and SPI are very famous, In this article, I will discuss the difference between I2C and SPI ( I2C vs SPI ). I2C and SPI both are bus protocol to allow the user for short-distance, serial data transfer. I2C is two-wire communication made by Philips (Nowadays NXP) and SPI is made by Motorola. Both protocols are commonly used in electronic devices like smartphones, TV, and laptops to control peripherals like power management chips, memory devices, input devices, etc.

What is I2C?

I2C is a serial communication protocol. It provides good support to the slow devices, for example, EEPROM, ADC, and RTC etc.I2c are not only used with the single board but also used with the other external components which have connected with boards through the cables.

I2C is basically a two-wire communication protocol. It uses only two-wire for communication. In which one wire is used for the data (SDA) and other wire is used for the clock (SCL).

In I2C, both buses are bidirectional, which means the master able to send and receive the data from the slave. The clock bus is controlled by the master but in some situations slave is also able to suppress the clock signal, but we will discuss it later.

Additionally, an I2C bus is used in the various control architecture, for example, SMBus (System Management Bus), PMBus (Power Management Bus), IPMI (Intelligent Platform Management Interface), etc.

Read the article to know I2C protocol in detail: Understanding of I2C Protocol.

Advantages of I2C communication protocol

There is a lot of advantage of I2C protocol which makes the user helpless to use the I2C protocol in many applications.

• It is the synchronous communication protocol, so no need of precise oscillators for the master and slave.
• It requires only two-wire, one wire for the data (SDA), and other wire for the clock (SCL).
• It provides the flexibility to the user to select the transmission rate as per the requirements.
• In I2C Bus, each device on the bus is independently addressable.
• It follows the master and slave relationships.
• It has the capability to handle multiple masters and multiple slaves on the I2C Bus.
• I2C has some important features like arbitration, clock synchronization, and clock stretching.
• I2C provides ACK/NACK (acknowledgment/ Not-acknowledgement) features that provide help in error handling.

Some important limitation of I2C communication protocol

An I2C protocol has a lot of advantage but beside it, I2C has a few limitations.

• It consumes more power than other serial communication busses due to open-drain topology.
• It is good only for a short distance.
• I2C protocol has some limitation for the number of slaves, the number of the slave depends on the capacitance of the I2C bus.
• It only provides a few limited communication speed like 100 kbit/s,400 kbit/s, etc.
• In I2c, devices can set their communication speed, slower operational devices can delay the operation of faster speed devices.

What is SPI?

The serial peripheral interface is four wire-based full-duplex communication protocol these wire generally known as MOSI (master out slave in), MISO (master in slave out), SCL (a serial clock which produces by the master) and SS (slave select line which use to select specific slave during the communication).

SPI follows the master and slave architecture and communication is always started by the master. Like I2C it is also a synchronous communication protocol because the clock is shared by the master and slave.

SPI is supported only multi-slave does not support multi-master and slaves are selected by the slave select signal. In SPI during the communication data is shifted out from the master and shifted into the slave vice- versa through the shift register.

Advantages of SPI communication protocol

• There is no start and stop bits, so the data can be streamed continuously without interruption.
• It supports full-duplex.
• No need for precision oscillators in slave devices as it uses a master’s clock.
• No complicated slave addressing system like I2C.
• Higher data transfer rate than I2C (almost twice as fast).
• Separate MISO and MOSI lines, so data can be sent and received at the same time.
• Simple software implementation.

Disadvantages of SPI communication protocol

• If there is more than one slave in communication then the wiring will be complex.
• Uses four wires (I2C and UARTs use two).
• No acknowledgment that the data has been successfully received (I2C has this).
• No form of error checking like the parity bit in UART.
• It only allows for a single master.

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In the embedded system, I2C and SPI both play an important role. Both communication protocols are the example of synchronous communication but still, both have some important differences. In the below table, I have pointed out some common differences between SPI  and I2C ( SPI vs I2C ).

The important difference between I2C and SPI ( I2C vs SPI ) communication protocol.