No twi readings on battery

[Ceranthor]

Hi,
I have strange problem. I have LSM9DS1 IMU connected to nrf52840. when i supply 3.3 V from external source (Nano 33 BLE) and to the J-link everything works. But if I switch to battery source (2 AAA batteries) 3V there are no readings from IMU. It is connected and twi scanner detect it but I cannot read registers. I supply power to the IMU via GPIO port set to high. Current draw is about 3 mA so it does not exceed the maximum GPIO output power. I also have external 4.7K resistors for SDA and SCL lines. What can be a problem?

[Kenneth]

You have connected GND between the two boards also? Is there a difference with/without j-link connected? Have you connected a logic analyzer to the twi?

Kenneth