I2C Devices Not Detected After Extending Wires to 10ft on Beaglebone—How to Fix?

Hello,

I am working on a project for school. I have a Beaglebone connected to a RTC, MPU6050(gyro/accel), and 2 ADXL345(accel) devices connected to a breakout board I created. I recently replaced the short (~8in) wires to the sensors with longer (~10ft) of wire and a connector in the middle. Since then I have lost communication with the RTC.

The RTC is connected directly into the board. The rest of the sensors are connected via 4 wires. If I disconnect the SCL wires to the sensors, I am then able to see the RTC again. Disconnecting the SDA, VCC, or GND from the sensors does not affect the behavior.

I've done a continuity check from sensor to the breakout board and they all check out. The i2c bus is running at 100khz. I am certain the extra wire I have added is the root of the problem. Is there anything that can be done to fix it? Thanks in advance.

Diego

This is not my area of expertise, but right off the bat I would say you need line drivers and or termination.

What is probably happening is because the signal frequency is as high as it is, and the wires are that long, there are reflections that are interfering with the signals.

There are ways of dealing with this that involve line drivers and/or termination resistors (to properly match the impedance of the line(s)).

Check these out:

* http://www.esacademy.com/en/library/technical...us/general-introduction/i2c-bus-hardware.html
* https://getsatisfaction.com/thingm/topics/length_of_i2c_bus
* http://avrhelp.mcselec.com/using_the_i2c_protocol.htm [scroll to end]

Thanks. I think this is exactly what is happening.