STM32 SPI Hardware CS

khalid2 · ‎2014-07-01

Posted on July 01, 2014 at 12:40

Hello,

I'm using a STM32F30x as a Slave. The Master is a custom board that select/deselect the Slave by toggling an output pin.

In the Slave side i configured the SPI with hardware management, SPI_InitStructure.SPI_NSS = SPI_NSS_Hard;

There is no difference when it's managed by software SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;

Someone could have an idea what the difference ?

Thanks in advance

khalid2 · ‎2014-07-07

Posted on July 07, 2014 at 15:48

Is there always the problem of Hardware CS with STMF3?

I tried to manage it but no success.

Someone made it work ?

zoharr · ‎2014-07-07

Posted on July 07, 2014 at 17:34

Hi,

I'm using STM-L1 and not STM-F3 as SPI slave with hardware CS, but I think this can help.

I defined the NSS pin in the STM-L1 (SPI slave) as external interrupt with trigger falling. This EXTI indicate the master select the CS and ready to transfer SPI data.

khalid2 · ‎2014-07-14

Posted on July 14, 2014 at 19:46

Thank you rogel.zohar for your help.

I did the same as you but the problem is that there is no difference between:

SPI_InitStructure.SPI_NSS = SPI_NSS_Hard; and SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;

For me a hardware CS is when we don't need to use an external interrupt to detect it. It should operate automatically. May be I make a mistake about the CS stuff.

Someone can highlight this point please ?

B.R