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I2C Cables Over Long Distance

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  • I2C Cables Over Long Distance

    We've found an article discussing problems with running an I2C cable to sensors over a long distance and some solutions that prevent miscommunication and glitches running along these long lengths. They recommended a shielded cable with multiple leads that include a grounding wire at one end, however, our team would like to know what “grounded” might mean in the context of our FTC robot? Is it enough to attach one end of the grounding wire to the metallic frame? Thanks!

  • #2
    Perhaps what is needed is an Expansion Hub without motor ports. Let's call this a "REV I/O Hub":

    Without motor ports, the I/O Hub's packaging is smaller than that of the Expansion Hub. There can be variants of the I/O Hub having different configurations/subsets of I2C, PWM, analog, and digital ports.

    Any number of I/O Hubs would be allowed on the bot for the purpose of minimizing I2C, PWM, analog, and digital cable lengths. The I/O Hubs connect to the Control Hub, or to an Expansion Hub, via the RS-485 network.

    Since the RS-485 network can be up to 1200 meters in length, I am assuming the reason that the differential signal wires of REV's RS-485 cable (aka "JST PH 3-pin Communication Cable") are not twisted together is that RS-485 cable lengths on a bot are short enough that the signal wires need not be twisted together ???