Just to add to this: place the inline resistance (try 20 - 200 Ohms) at the driving side of the signal lines.
If you imagine the wire as a capacitor, you want this inline resistance to limit the current that this capacitor is charged with in order to reduce the ringing.
Thanks for the explanation, @recursinging. For my application, higher speeds aren’t needed, what I really need is more flash. After getting my test code running, I added FatFS to my real code and was 5KB over limit. Guess I need to go back to trying to figure out why my QSPI-based patch storage scheme very occasionally wipes clean.
Hi everyone.
I had no issue with my Pod and no issue with my breadboard too!
The troubles came when I added the SD card reader with daisy on a protoboard. Changing the GPIO speed did the trick.
I should try to add some 20R on the way too!
I just wanted to report that as of this post, January 2023, the above mentioned changes regarding SDIO speed set to low appear to still be necessary to make a seed board use the Adafruit SDIO SDMicro breakout card also mentioned in this thread.