How to get faster SPI with Xiao SAMD21?

[msfujino]

It’s been a while, so I had forgotten about it, but I think the link below will be helpful.

XIAO SPI Speed slower than a UNO

I’m using SPI for a MCP4802 DAC which I tested first with a UNO and have now hooked up to a Seeeduino XIAO expecting a faster speed, given the clock is 4 times as fast but it’s actually a little bit slower! The DAC can handle up to 20MHz which is probably much more than either the XIAO or the UNO can manage. Just uploading 0 and 128 in a loop to get a square wave my scope is showing a miserable 12.7kHz, i.e. two channels of 8 bits uploaded at a rate of 25,400 per second. With the UNO, I can …