Some questions about i2c and breakout boards/shields

Projects General Guidance
1

Hi guys, i am working on a project that will eventually have quite a few sensors on the i2c bus, most of them on breakouts, some of them not.

My question is the following, in order for the i2c bus to work correctly 10k pullup resistors are needed to pull the signal lines high when no bits are being sent. On breakouts these resistors are included. Is there some risk in piggybacking multiple breakouts, in the sense that the pullup resistors will all be in parralell and thus the resistance between vcc and the signal lines will be further reduced with each consecutive breakout?

Next question; If I have a sensor on a breakout with pullups included, can I connect another i2c sensor without a breakout on the bus, and the pullups on the breakout will also work for the sensor without a breakout?

2

Hi,
Having a number of I2C each with pullups will cause a a problem as they will all be in parallel.
So you may need to remove the pullups to minimise their loading effect.

A module with no pullups will work with a module with pullups.
The resistors are there for the I2C bus, so even one set of pullups would be enough for many I2C devices with resistors not locally fitted.

Tom... :slight_smile:

3

Perfect, thankyou for the info!

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