What The Tech?! The UART

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1 Dec 2025

In just a few decades, we went from magnetic tape to the cassette, before moving to the Compact Disc and eventually, fully digital and streamable media. And while these iterations provide huge benefits around things like storage capacity or quality, this rapid shift between generations provides humanity with a unique problem.

“How do we standardise communication on the firmware level with such a vast range of different protocols and hardware types?”

If you’ve ever been driven crazy by driver or port issues working with hardware, you probably don’t need to be told that it’s a problem that remains relevant, even today. However, we weren’t snoozing on this type of thing, and while one particular invention wouldn’t solve the issue. What it would do, though, was help to standardise much of this communication, while laying the framework for our more modern IOT devices.

It would also lay the groundwork for modern debugging and contribute greatly to the development of architecture around embedded systems. The fact that it’s little known outside electronic circles makes the humble UART humanity’s quiet achiever.

Early Beginnings

Designed in the 1960s, the Universal Asynchronous Receiver Transmitter was originally designed to simplify communications between computers and peripheral devices.

It aimed to do this by reducing the multiple-wire system used by parallel ports down to just two primary lines: TX (transmit) and RX (receive). This would allow devices to communicate reliably without the need for an external clock signal to harmonise things.

The invention of the protocol and hardware has an interesting background, as rather than being attributed to a single person, its overall design was improved and standardised by several companies. However, it would be Gordon Bell of DEC who would originally lay out the initial design for the UART, with DEC taking the reins and expanding the system beyond that.

One contributing factor to the success of the UART would be the status and market position of IBM Computers in the 1970s when the system would first start to see broad use. With IBM’s business machines dominating the commercial world and the Personal Computer market being nowhere near fully developed, their adoption of the UART design would lay the foundations for the system to receive much more ongoing research and development.

It would also mean that other companies would follow IBM’s lead, integrating UART systems into their own designs.

How UART Works

UART converts parallel data from a CPU into serial form for transmission, and vice versa on reception. This gives the UART versatility, as it also allows for the uploading of firmware as well as debugging.

Data is sent in packets or frames, with start bits, data bits, optional parity bits, and stop bits. Because it’s asynchronous, sender and receiver must agree on a baud rate, but do not share a clock.

This simple, yet effective design, along with its easy implementation, is part of the reason it became a simple, reliable standard for point-to-point communication in electronics. With the future of electronics leaning towards small, surface-mounted designs, UART had plenty to offer modern embedded designs.

Modern Applications

Despite its simple design, UART is highly relevant, even more so when you consider some of the hardware that powers our connected world. More importantly, the UART also allows us to tackle more modern hardware on a foundational level.

In some ways, the presence of the system made it easier to hack, repurpose and recycle hardware as it enabled us to communicate with devices with almost trivial ease. A great example of this is an internet router. While it is delivered to the end user in a ready configuration, with a UART cable and a laptop, we can download and then analyse the firmware.

If we aren’t interested in using it in this standard configuration, we could also reflash it with new firmware, which gives it new or expanded features and, in some instances, repurposes the system entirely. Some patience and a cable that costs just a few dollars can open up a whole new world of exploration and design.

While the modern application of it is broad, taking the time to learn the fundamentals makes it much easier to develop your knowledge. SoC, FPGA’s and microcontrollers all use UART systems that are open to exploration and exploitation.

Legacy

Electronics is kind of neat in that we started by talking about the rapid evolution of modern systems and closed by acknowledging that the UART system had a legacy that has lasted for more than 5 decades. This helps to highlight an important point: Despite rapid evolution, there’s still plenty to be offered by robust, simple protocols that “just work”, a point that remains relevant even today.

With the UART being a key player in enabling console debugging, firmware updates, and hardware analysis, the simplicity of the system means its legacy will not just endure, it will continue to grow. UART will rightly remain a foundational step for electronics students and hobbyists, teaching core concepts of data transmission, timing, and protocol design.

The fact that UART still works so well in modern designs reminds us that simple technologies often outlast much flashier innovations.

What The Tech is our recurring, twice-monthly piece that looks at the technology that was essential in shaping our modern world.

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