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I²C multiple sensors pullup (with schematic)


#1

Hi,

I received my I²C differential extender (Polulu 2159 which doesn’t include pullup according to datasheet) and Polulu VL53L0X sensors and here is the schematic of what I am planning to do, including cables length:
schema%20i2c

Do SDA, SCL pullups are correctly placed? should I have a pair of pullup per device or a pair of pullup for the whole line?

Regards,

Jim


#2

Hello, Jim.

There are 10K pullups on our VL53L0X boards. Adding additional 4.7K pullups like you put in your schematic would not exceed the I²C specifications for a 5V bus, but they might not be necessary either.

The schematic in the datasheet for the I²C extender board from SJTbits indicates it uses a bidirectional bus buffer to isolate the devices connected to the SDA and SCL pins on the board (and the ICs that handle the differential signaling provide further isolation), so the pull-up resistors on those pins on one I²C extender board should not affect devices connected to a different I²C extender board.

-Nathan


#3

Hello Nathan,

Thank you for your advice, I will give it a try without pullups and let you know how it works.
Have a good day,

Regards,

Jim