SPI vs. I2C: Serial Communication Protocol Comparison

This article compares SPI (Serial Peripheral Interface) and I2C (Inter-Integrated Circuit) communication protocols, highlighting their differences in a tabular format. We’ll explore various aspects, including interface diagrams, pin designations, data rates, communication types, clocking mechanisms, hardware and software complexity, advantages, and disadvantages.

SPI Interface

Key Features of SPI:

• Originally developed by Motorola and widely adopted by various silicon device manufacturers.
• Utilizes four signal lines between the master and slave devices:
  • MISO (Master In Slave Out): Data line for the slave to send data to the master.
  • MOSI (Master Out Slave In): Data line for the master to send data to the slave.
  • SCLK (Serial Clock): Clock signal generated by the master to synchronize data transfer.
  • SS (Slave Select): Used by the master to select a specific slave device for communication.
• Supports full-duplex and bi-directional communication due to the presence of separate MISO and MOSI lines.
• Employs synchronous communication due to the SCLK line.

I2C Interface

Key Features of I2C:

• Developed by Philips (now NXP Semiconductors) to enhance hardware efficiency and simplicity.
• Employs only two signal lines between masters and slaves:
  • SCL (Serial Clock): Clock signal generated by the master.
  • SDA (Serial Data): Data line for both master and slave to transmit and receive data.
• Often referred to as a “Two Wire Interface.”
• Supports multiple masters, though typically a system consists of one master and multiple slaves.
• The master controls the clock signal, and the slave device is selected via a 7-bit address.
• Data transmission is initiated with a START condition and terminated with a STOP condition.
• Each byte transmitted is acknowledged (ACKed) by the receiver.
• The data packet includes the slave device address, a Read/Write operation indicator, and the data itself.

SPI vs. I2C: A Detailed Comparison