Hi @Sean Wang This is crosstalk between signal wires or lack of ground connection. - As James pointed out, make sure you have proper ground connection between the devices. - Twist the signal wires with a ground wire, specially the CS and CLK (or use shielded wires). To reduce ringing use termination like series resistor. Similar to the HS adapter: https://digilent.com/shop/digital-discovery-high-speed-adapter-and-logic-probes/