SPI speed connect wiem

I read that because of the filters SPI does not work well if running too fast.

What kind of speeds you have been using without problems?

You are correct: the EM’s SPI speed is limited by the RC filters. At about 100kHz the rise and fall times are already pretty rounded. You may be able to get it to go a little faster than that but I don’t think I’d trust the reliability of it.