I2C pull ups and 3V3S supply

[maadrad1 (John Jimmy Trivette)]

Hi,
Im using a RAK4631 on a RAK19007. I’m having a problem and I wonder if this is a problem others have already solved. I have an external I2C sensor connected to the I2C1 pins and powered by the 3V3S supply. I’m using that 3V3S ability to turn off to shut off the sensor. This works good except - my sensor has pull-up resistors on the I2C pins. When the 3V3S supply is off the nRF is powering my sensor by feeding power back thru my pull-up resistors to the +V supply. At least that’s what I think is happening… The idle state of I2C is to go HIGH on both lines right.

Could I solve this by having the nRF I2C pins go low while the 3V3S supply is turned off?
Or maybe a blocking diode on my pull-ups

[beegee (Bernd Giesecke)]

The easiest solution is to remove the pull-ups on your external sensor.

[maadrad1 (John Jimmy Trivette)]

Does the 4631 have i2c pull ups?

[beegee (Bernd Giesecke)]

The RAK4631 does not have I2C pullups, but the Base Boards like the RAk19007 have pullups on the I2C lines.