Compatibility issue with Arduino portenta C33

[lars2696]

Compatibility issue with Arduino portenta C33

[peterpolidoro]

That is frustrating, but interesting. I do not know why the portenta SPI would behave so differently. It is very strange that the MOSI line would be changing before the clock. I can see it changing once to put it into the proper initial condition, depending on the SPI mode, but changing twice seems suspicious.

I have never used the portenta, but I suspect it might be some issue with how you are using their SPI library. I am not sure what could be in this library to cause such a problem, but perhaps.

It would be great to figure out how to make this work, but right now I do not have many ideas other than reading about potential issues with portenta SPI.

[lars2696]

I still think it has something to do with the 3.3V operation mode. I just noticed that in these screenshots the IC is still in 5V mode (MISO response is up to 5V). I currently don't have access to an oscilloscope. When i get the time to test that i will give updates, but since i have deadline, will switch to a different µC.