I2C on long cable

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I2C on long cable

Unread postby oleg » Fri Jun 15, 2018 3:50 pm

Hello everybody!

I was trying to connect i2c sensor to odroid xu4 on long cable - 30cm
I am using shifted shied in 5v mode. And on short cable (10cm) everything was ok but on long cable Odroid doesn't process anything.

So I disconnected my sensor and use i2c tool to check what I got
2018-06-15_0938.png
2018-06-15_0938.png (21.57 KiB) Viewed 40 times


Then I connected long cable without sensor and got
2018-06-15_0947.png
2018-06-15_0947.png (30.1 KiB) Viewed 40 times


So, my question is, how can it be that even with empty wires Odroid XU4 things that something was connected

Thank you
oleg
 
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Re: I2C on long cable

Unread postby odroid » Fri Jun 15, 2018 4:52 pm

The TSX0108E IC on the Shifter Shield caused the problem due to very weak driving capability.
https://www.hardkernel.com/main/products/prdt_info.php?g_code=G143556253995

When the cable is very long, we have to use a different level shifter(BS138) something like this.
https://www.sparkfun.com/products/12009
https://wiki.odroid.com/odroid-xu4/application_note/gpio/1wire
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