What You Must Know About These 5 Serial Communication Protocols

Serial communication in the world of telecommunications is the sequential transfer of data one bit at a time over a communication channel or communication bus. Usually, this transfer of information happens between two or more components of embedded systems. In comparison, parallel communication sends several bits of information as a unit all at the same time.

Advantages of  Serial Communication

While parallel communication might seem simpler, serial communication is more economical in terms of long-distance communication, or cable channels that span long distances. Transmission speeds and signal integrity are also becoming stronger making serial communication a better option today even when it comes to communication across shorter distances.

Although it would seem parallel communication should be faster than serial communication, which would make it seem like the optimal choice, the reality is that serial communication requires fewer cables to transmit the data and there is less crosstalk, undesired signal glitches happening from one channel to the next. When there are fewer conductors — and there are fewer conductors present when serial communication is used — there are fewer inconsistent signals. The end result is serial communication generally offers superior performance and speed.

Serial Communication Port

Why is serial communication necessary? To function properly and keep your world connected, embedded systems need to be highly functioning and continuously interpreting, cycling, updating, and sharing information. When a microcontroller in an embedded system contains a particular data set, it is stored in parallel form but converts to serial data when it is transferred to the output buffer. When receiving data, the microcontroller on the other end can convert the information back to a parallel form.

In order to keep your ever-modernizing world connected at the speed you’re accustomed to, serial communication protocols have been created to process digital information securely, efficiently and smartly. In this piece, we will dive into five serial communication protocols you should know in order to stay up to date on how embedded systems are communicating second by second, day by day.

CAN Protocol

The Controller Area Network (CAN) protocol was created with the intent to minimize and downsize communication processes in automobiles. Robert Bosch, the developer of the CAN protocol, recognized the need to make intelligent vehicles more affordable and practical.

Cars in the late 1970s were just beginning to see changes such as anti-lock braking systems, air conditioning, central door locks, airbags, gear control, and management systems. All of these advanced features meant more complex designs and heavier-duty mechanical parts that were more expensive than ever before. To keep expenses low and simplify the in-vehicle wiring and machinery, he implemented CAN.

What CAN Supports

Engineers producing new vehicles could now manage the electronic subsystem in cars with a single cable. The microcontrollers and devices within the network could now communicate with each other without a host computer. It is message-based and now used in various manufactured applications such as cars, trucks, and buses — both gasoline powered and electric — as well as aviation equipment, automated machinery, elevators, and medical equipment.

Total Phase offers two types of CAN products: the Komodo Solo CAN Interface and the Komodo Duo CAN Interface.

I2C Protocol

Think about switching your tablet screen to night reader mode and the way the colors invert to make reading easier on your eyes. Now consider when you move from a dark room to a brightly lit area and how you might need to boost the brightness on your phone screen in order to read a text. These applications are using the I2C protocol.

The Inter-Integrated Circuits (I2C) protocol has been around for three decades but is still widely used in embedded systems today. Designed by Philips Semiconductor (now NXP Semiconductors), I2C attaches lower-speed integrated circuits to processors and microcontrollers used in short distance communication. Engineers can thus connect multiple slave devices to one or more master devices on the same printer circuit board.

What I2C Supports

This protocol is more often used when simplicity and economy are more important factors than speed. Some applications that implement the I2C protocol include: real-time clocks, extended display identification data for computer monitors via VGA or HDMI, volume settings in embedded speakers, and small LCD displays.

Unlike the CAN protocol, two wires are used for data transmittal in I2C. You should note that I2C uses pull-up resistors, which physically interrupt component connection within switches and transistors. They are, however, flexible when it comes to speed and functionality.

Total Phase offers three I2C products: the Aardvark I2C/SPI Host Adapter, the Beagle I2C/SPI Protocol Analyzer and the Promira Serial Platform.

SPI Protocol

Similar to I2C, the Serial Peripheral Interface (SPI) protocol is used for short distance communication. The difference with SPI is that it only implements one master and it needs four wires to communicate. One or more slaves can be supported through SPI by adding additional additional slave select lines. Motorola developed the interface in the mid-1980s and it has become a common synchronous serial communication protocol since then.

The four signals transferred over four wires include Master Out Slave In (MOSI), Master In Slave Out (MISO), Serial Clock (SCK) and Slave Select (SS). SPI interfaces can support data speeds over 100 MHz, versus I2C, which supports up to 3.4 MHz.

What SPI Supports

The SPI protocol is used mainly in SD cards, LCD interfaces, reading data from real-time clocks, and applying for communication with temperature, pressure sensors, and video game controllers.

Total Phase has four SPI products for you: the Aardvark I2C/SPI Host Adapter, the Beagle I2C/SPI Protocol Analyzer, the Cheetah SPI Host Adapter, and the Promira Serial Platform.

eSPI Protocol

The Enhanced Serial Peripheral Bus Interface (eSPI) protocol was designed by Intel to reduce the number of pins used on the motherboard. It downsized and simplified a number of other processes at the same time. The eSPI protocol reduces the voltage necessary to facilitate smaller chip manufacturing processes, providing greater available throughput than the previous LPC bus. The eSPI bus can also be shared with SPI devices.

What eSPI Supports

Before eSPI, the Low Pin Count bus (LPC) was used for IBM-compatible personal computers. It allowed low-bandwidth devices such as CD ROMs to connect and transmit data in a multiplexed four-bit wide bus. Now, the eSPI protocol is used mostly where real-time flash sharing is required.

Total Phase has one eSPI product for you: the eSPI Analysis Application for the Promira Serial Platform.

USB Protocol

The Universal Serial Bus (USB) protocol, created in the 1990s, is one of the most popular means of connectivity for modern devices. Nowadays, USB drives can charge phones, connect phones to printers, connect hard drives to laptops, or even connect disk drives to laptops in order to watch a DVD you own that might not be on Netflix just yet. In many cases, USB has replaced older means of communication like RS-232 and SCSI. There are a variety of different USB connection types. In addition to the Standard-A and Standard-B connections found on many peripherals, micro-USB, mini-USB, and the reversible USB Type-C connector are also popular.

USB 2.0 (a.k.a. “High-speed” USB), which was released in 2000, is the most commonly used USB standard. Over the past few years, USB 3.0 (SuperSpeed USB) and 3.1 (SuperSpeed+ USB) have been growing in popularity. USB 3.2 was released in August 2017 and is only beginning to be adopted by consumers and businesses.

From backward compatibility perspective, USB 2.0 devices can be used in a USB 3.x port. Similarly, a USB 3.0 device can be connected to a USB 2.0 port. However, in both cases, you would not achieve USB 3.x speeds and would be limited to the 480 Mbps speeds of USB 2.0

What USB Supports

From a communications perspective, up to 127 USB devices can communicate on a single USB bus. In addition to data communications, USB connectors can also charge devices. USB 1.x and USB 2.0 used 4 wires. Two for communication (Data- & Data+) and two for power (VBUS & Ground). USB 3.x increases the complexity and feature set by increasing the wire count to nine. For a deeper dive on USB protocols, including USB 2.0 & 3.0 signaling, USB enumeration, USB descriptors, & USB architecture, check out our USB Background article.

Total Phase offers multiple USB products: the Beagle USB 12 Protocol Analyzer, the Beagle USB 480 Protocol Analyzer, the Beagle USB 5000 v2 Protocol Analyzer, along with the USB Power Delivery Analyzer for PD analysis and the Advanced Cable Tester v2 for cable testing.


Modern serial communication protocols are necessary when it comes to streamlined communication between embedded devices. The more complex connected devices and the Internet of Things seem to become, the more protocols there are making sure that the transfer of data is seamless and fast enough to keep you running at a high speed.

No matter what type of business you do, Total Phase is here to support your data transfer from device to device. We can help you choose the best product for the type of work you do - you can contact us by email or request a demo.