The SPI https://911electronic.com/spi-communication-how-spi-works/ belongs to the full-duplex interfaces, which means sending and receiving a signal at the same time. The SPI interface belongs to the family of synchronous interfaces, i.e. clock signal transmission, which allows synchronization of any system connected to the interface. The MASTER system is responsible for generating the SPI clock signal and starting the transmission of the signal. Other circuits connected to the same SPI interface take the form of SLAVE.
Which module do you use? Please let me know first. Thanks!