Hi All, @Doc TB, @leonvs
For the 24 input only pins of the Digital Discovery, Digilent offers the High Speed Adapter and Logic Probes. This is a small PCB adapter which extends the number of GND pins to 24, one for each DIN. Each Logic probe is a set of twisted wires, (black for GND, red for DIN), with a 100ohm series resistor on the top of the red wire (for reducing reflections). This solution reduces crosstalk and enables high frequency signal acquisition.
https://digilent.com/shop/digital-discovery-high-speed-adapter-and-logic-probes/