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SPI Response

jdcowpland
Associate II
Posted on January 22, 2014 at 18:50

Hi guys,

I have SPI1 set up on my STM32F4 Discovery board to communicate with a Wiznet W5500io ethernet board. I'm sending it commands which I expect responses to, but I'm getting no answer. I know the module is working because I can see it doing other things on other pins. It's an SPI slave device though, and so I'm a bit confused as to how it will respond when it doesn't have control over the clock. Is there a setting somewhere to enable the clock permanently or am I misunderstanding SPI in some way. This is a picture of what I see on my SPI lines at the moment: 

0690X00000602qsQAA.jpg
1 REPLY 1
chen
Associate II
Posted on January 22, 2014 at 19:14

Hi

''Is there a setting somewhere to enable the clock permanently or am I misunderstanding SPI in some way.''

Yes, you miss-understand SPI

http://en.wikipedia.org/wiki/SPI_bus

The SlaveSelect(SS) line must be low.

MOSI is the data from master to slave

MISO is irelevant when master is sending.

SCLK is only active when SPI transmission is active.