If we don't use GPIO in ADBMS1818, Any connection is required? (we'll use no connection to GPIOn pins )
If initial setting is input (Din,SDI,CLK), pull down or pull up are required.(I think.)
Thank you very mcuh.
GPIO pins can be left open if not being used. even if the initial GPIO setting is configured to input since you are not planning to use it you can leave it open.
Are you instead asking information about external connections on the SPI lines? Then yes you will need to a Pull up of 2k for the SDO line and if your microcontroller does not have any internal pull up for CS pin then an external pull up is advisable
GPIO3, 4 and 5 pins can be used to control a secondary SPI/I2C device from ADBMS1818 by programming the COMM register and sending it out with STCOMM command. Do you intend on using this feature?
But as per your initial query you have mentioned that you will not use any GPIO pins so in this case they can be left unconnected. You do not need to connect any additional PU or PD to these pins.