Does long SPI lanes require extra attention?
In my case a SPI connection (initially separate loose wires) did not work reliably until I noticed that the clock lead really &quot;likes to be&quot; near the ground lead - suddenly starts working much better. But it was a slightly larger distance, about 30 cm wires between the two separate PCBs.
In response, I have used the ribbon cable with every second wire grounded, and all four SPI signals in between. The connectivity is now reliable. Maybe I have over tried with the measure so draconian but at least one less thing to worry about in my design.