LTC4311 I2C Extender

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adafruit_support_bill
 
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Re: LTC4311 I2C Extender

Post by adafruit_support_bill »

The chip may be getting power indirectly via the pullups. But it is not designed to work that way. For use with 5v devices you should power it with 5v via the VIN pin.
Three Arduino Uno and one Mega is connected on my battery and share 5V and GND.
An indirect GND connection via the power source may be subject to ground bounce and other interference. For a stable signal reference, you should have a direct GND connection to the bus.

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Stef94
 
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Re: LTC4311 I2C Extender

Post by Stef94 »

Does it means, that I have to connect the GND and 5V wire to the Mega from where I have took the SCL/SDA connection?

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Re: LTC4311 I2C Extender

Post by adafruit_support_bill »

The 5v you can get from any source. But there should be a direct GND connection from the Mega to the i2c bus.

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Stef94
 
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Re: LTC4311 I2C Extender

Post by Stef94 »

Okay. But that is strange anyway! If I connect only the GND to the Uno which is connected over the battery with the Mega it works, and if I connect the 5V from the Uno too it does not works anymore.
I will try it tomorrow to solder the 5V and GND wires also to the Mega and test it again. Hope that solves the issue!

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Stef94
 
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Re: LTC4311 I2C Extender

Post by Stef94 »

One thing of a little mystery, is the special resistor with 4x10k in one part. Is it similar to four separately 10k resistors or does it something special that is needed to know? Tomorrow I will measure the resistance there to figure out where the 5V come from.

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Stef94
 
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Re: LTC4311 I2C Extender

Post by Stef94 »

I have connected the I2C extender directly to the Arduino Mega with all wires (VCC, GND, SCL, SDA) and it works now! If the 5V and GND are connected to another Arduino from the I2C bus, it will not work.
Thanks a lot for your help!

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Re: LTC4311 I2C Extender

Post by adafruit_support_bill »

All devices on the bus should have a direct connection to at least GND, SDA and SCL. The GND is the reference against which SDA and SCL are measured. So a less than perfect GND connection will result in less than perfect clock and data signals.

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