Control SPI chip select

[webmeister]

I need to keep the SPI chip select asserted while transferring multiple messages (and doing some processing in between). The necessary low-level interface already exists (_CSpiIocTransfer.cs_change). Can this be made accessible from the high-level Python interface (i.e. SPI.transfer)?

[Livius90]

Duplicated issue: #37, vsergeev/c-periphery#19

It would be useful for me also. I made a modified def transfer_burst(self, data): method to do it. I could send it in a pull-request.

But pay attention that not all SPI controller driver can support it, i had to implement it in spi kernel driver for my SPI controller, too.