I am using these (https://sandboxelectronics.com/?p=3988) to extend the range of the I2C bus.
They work just fine with Atlas peristaltic pumps, Sparkfun SCD30, and Atlas non-isolated carrier boards.
They don’t work with Atlas isolated carrier boards. i2cdetect -y 1 does not show the addresses of the isolated boards.
I have followed the recommendation on the I2C extender datasheet to disable the pull-up resistors with no change.
This may be beyond the scope of this forum, but I’m stumped as to why.
Any help would be appreciated.
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I’m not familiar with that device, but I know the LTC4311 works well to improve I2C signal over long distances and only requires 1 to work (connected near the computer).
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I’ve tried the LTC4311, however it didn’t like daisy chaining I2C over the distances I’m shooting for.
Thank you for your quick response.
The problem you’re going to have with either device over very long distances is going to be voltage drop. You can avoid this by providing 3.3 volts (or 5 volts, depending what you’re using) at the terminal end of the long wire, where the sensors are. The only thing that needs to be connected, power-wise, is ground. Since I2C is open-drain, communication occurs by dropping the communication wire voltages to ground, but to have a strong signal, the voltage needs to be adequate. Having to traverse the entire length to the sensor and back can produce significant voltage drop. By generating the voltage at the sensors, you effectively reduce the voltage drop by half since the distance is now only from the sensors to the computer rather than from the computer to the sensors to the computer.
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