RC filter in SPI MISO line
You would need a properly attached 500MHz or better scope to see the ringing on a 1m cable with 5ns prop delay.

SPI was never intended for long cables.

this is a transmission line theory type question best understood by impedance ratios and stand wave ratios. Essentially 5:1 ratio cable:source R can cause &gt;50% ringing

Diode clamps dampen by overvoltage ESD protection diodes built into CMOS devices. This also improves reflections greatly in a cable.

SPI comes in many configurations of open drain with pullup R and push-pull low impedance.

SPI chips are designed to be slower (than std 74HC logic) and thus effectively have internal LPF with ~ &gt;=100 ns prop delay.  Clock speeds on IC's are rated from 0.4 to 26MHz so your results may vary with pullup R.


There is no obvious benefit from an RC filter, but other factors not mentioned may or may not impact this at maximum cable lengths and high bit rate.

a 1m cable only has ~ 5ns prop delay.

here interactive switches using 1m cable with 50 Ohm source and 5pF load and dominant ringing at 40MHz.