How Far Can I2C Go? -- Episode 666

Have you ever wondered if the humble I2C protocol, designed for short-distance communication on a PCB, could work over a stretched-out distance? Clem, an innovative DIY enthusiast, dives headfirst into this question in his latest experiment. Armed with two Raspberry Pi Pico microcontrollers, a coiled-up RG58 coaxial cable, and a few unconventional ideas, he sets out to see if I2C can bridge the gap between devices separated by meters—even outdoors.

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How Far Can I2C Go? -- Episode 666

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The Problem: Taking I2C Beyond the PCB

I2C (Inter-Integrated Circuit) is a reliable protocol, but it’s typically intended for communication between components within a single PCB or, at best, over very short distances. The main challenge? Capacitance—as wires get longer, their ability to maintain signal integrity decreases. Clem had an ambitious thought: What if he could use I2C as a bus system running throughout his workshop to connect micro-controllers and sensors scattered across different areas? Could it work over 10 or even 20 meters of cable? Only one way to find out—test it.

The Setup: Breadboards, Raspberry Pi Picos, and Coaxial Cable

Clem began his experiment with a simple setup on breadboards. Using two Raspberry Pi Pico micro-controllers, he established a basic I2C connection with standard jumper wires to simulate a local, short-distance connection. With the baseline working, it was time to introduce the star of the experiment: a 10-meter-long RG58 coaxial cable. Why coaxial? Its shielding properties make it a good candidate for reducing interference, a critical factor when extending the range of I2C.

He connected the two micro-controllers through the coiled cable and ran initial tests. The results were promising—communication was intact! But Clem wasn’t done yet. He wanted to push the boundaries even further.

Taking It Outside: Testing I2C Over 20 Meters

With the system working over 10 meters of cable, Clem decided to push his experiment to the extreme. He ran the coaxial cable through a cellar window and out into his garden, effectively extending the distance to 20 meters. The sight of an I2C bus stretching through a garden might have seemed bizarre, but it was all in the name of science!

To his delight, the I2C communication still worked. By using the RG58 cable's shielding to his advantage, Clem demonstrated that the protocol could handle significant distances, far beyond its typical use case.

Bill of Materials

Supporting Code and Links

•  Supporting Files for Episode 666 of element14 presents  

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