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??

[Håkon Alseth]

Hi,

That indicates that an ignored transaction has occurred (DEF register is set to '0xaa' in the SDK example).

1. Have you tried reducing the frequency on the SPIMaster side?
2. Do you always see this issue?
3. Are you sure that your SPIM is within the timing requirements stated for the SPIS module (PS chapter 8.3)?

Best regards Håkon

[Håkon Alseth]

Have you set the same SPI mode on both sides? Could you try adding a delay of some microseconds after asserting the CSN line until you clock out data on MOSI?

BR Håkon