The DA14580 datasheet mentions that the i2c works in open drain mode.
However, I see a (valid) i2c signal without anything connected to the SDA / SCL pins, and no external pull up. The pins are configured as input without pull-up:
GPIO_ConfigurePin( I2C_SDA_PORT, I2C_SDA_PIN, INPUT, PID_I2C_SDA, false );
GPIO_ConfigurePin( I2C_SCD_PORT, I2C_SCD_PIN, INPUT, PID_I2C_SCL, false );
Can you please confirm whether there are internal pull up on the i2c pins?
If yes, what is their resistance? Can they be disabled?