SPI send dummy data

[MGaja.1]

Hello, I am using stm32f429i discovery boards for spi communication. I am using HAL libraries, trying to send dummy data, but my DR register is not getting updated, , I am using atollic truestudio, I kept the clock of both boards same can anyone help me?

[S.Ma]

Master side: Use DMA for both transmit and receive. Do use the 4 wire SPI and SW control NSS level.

Slave side: Use DMA with both TX and RX CYCLIC buffer. Implement EXTI on NSS to reset your DMA and/or process incoming message, so no interrupt from SPI nor DMA required.

For a single slave, you can keep NSS as general GPIO on the slave side.