I am designing hardware using STM32H7. I would like to connect three power monitor devices to SPI4 of MCU as slave devices, but SPI4 has only one NSS(slave select) pin. How should I connect these multi slave devices to SPI4 of MCU?

[LCE]

Use other GPIOs for NSS, pull them low before each SPI transaction, back to high again when done.

[EAbra.3]

Thank you very much for the prompt reply. Can I use any of the I/O pins for NSS or is there any particular GPIO pins for the same?

[EAbra.3]

I have one more question that, once I connected the GPIO pins as NSS, later I should control these pins using software. Am I right or not?

[LCE]

Yes, you have to control these pins "manually":

GPIO LOW

do SPI stuff

GPIO HIGH