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Why is SPI not working without a floating wire on the MOSI line in SPI?


I've connected the cno410 LED Driver to NUCLEO-F446RE which works with SPI lines, whenever I've linked to it directly, it works as expected. we have designed another PCB shield on the Nucleo board. On top of we have connected this LED Driver now. Now it is not working as expected. But whenever I've connected the logic analyzer it is working as expected ( which is not worked without connecting the logic analyzer).

Simply say SPI is working when I'm connecting the floating wire on the MOSI line and not working if there is no floating wire. I'm surprised by what is happening. I've checked all the grounding and all are well. Even though I tries to check with the logic analyzer LED driver is working.

What are the chances I may getting this problem please give any suggestions. I'm unable to debug it.

ST Employee

Welcome, @APinn.1​, to the community!

  • what is a cno410 LED driver, can you attach an URL to the data sheet or the data sheet itself?
  • how did you initialize / setup / control MOSI?



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