About SPI slave on 51422

[Elliot.Chao]

I use the SPI slave function on 51422. When I send a byte(0x31) to 51422 SPI slave from master, 51422 will back a byte (0xAA - DEF byte) to master. Why?

I send 0x31 every 1 seconds, but I always get 0xAA. Why??

[tetiana]

I have the same issue with nrf51822 board: 1. Yes 2. Yes 3. Yes. I'm also using STM32 discovery as a SPI master. Are there any updates for the issue? I don't have any other ideas what might be wrong :(