Length of I2C bus

  • Question
  • Updated 3 years ago
Someone on here described their I2C bus as "long" when it was only 4 feet. I'm planning on using some MaxM LED units in a display that requires several meters of cable between the Arduino and the units. Will this work okay?
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Posted 7 years ago

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todbot, Official Rep

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Official Response
Hi Adam,
It's true that I2C is designed as a "chip-to-chip" protocol, not something going over cables. But I've had I2C cables as long as 20 feet with no problems. You need 4.7k pull-up resistors on the two data lines. When people want longer runs, they use I2C line driver chips. We're currently evaluating a few and when we have some recommendations we'll post them here.

Since you're driving MaxMs, I suspect the larger problem will be getting adequate power to them. If you're using the MaxMs in the Master+Blaster configuration, each MaxM draws 1/4 Amp and most ribbon cabling can't do more than one Amp. You might need to run separate power cables to each MaxM.