I have two modules that uses I2C and both connected to an Arduino. one of them have two 10K pullup resistors.

The other one is an 16X2 LCD I2C:

I couldn't find an schematic for this module but tracked the connection with DMM.

Connecting the LCD I2C modules causes the first module (ADC) readings get way off.

Those two 4.7K are pullup resistors? if yes can I safely remove them because I have pullups on the ADC module?


Yes they are the pull-up resistors according to your measurements. The photo is not perfect but gives a hint that PCB tracks from resistors to IO expander chip SDA, SCL and VCC pins. Also Sunrom schematics confirm R8 and R9 are the I2C pull-up resistors.

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  • \$\begingroup\$ Thanks, do you have the schematic link? \$\endgroup\$ – ElectronSurf Feb 16 at 11:44
  • \$\begingroup\$ Not at the moment but try searching with "sunrom i2c lcd schematic". \$\endgroup\$ – Justme Feb 16 at 12:30

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