Use this scheme:

Components for ADC-shield:

• U1-mcp3201, dip-8
• P1 - BNC connector
• P2, P3 - TRG5-5VDC relay
• P4, P5-connector 2.54 mm pitch 13*2 pins
• P6, P7-connector 2.54 mm pitch 5 pins
• P8 - connector 2.54 mm pitch 3 pins
• Q1, Q2 - NPN 2n5551 — 2
• R1, R8-4.7 k, 0.25 W
• R2-5M, 0.25 W
• R3-4M, 0.25 W
• R4-1M, 0.25 W
• R5, R7-820, 0.25 W
• R6-100, 0.25 W
• D1-zener diode 2,4 v
• D2, D3-zener diode 4.7 v
• C1, C4 - 47µF
• C2, C3 - 0.1 µF
• ec11 encoder for arduino x2

If the output of the button on the Board is not pulled up (pull up) resistor, you need to add a 10 kOm resistor:

https://www.armbian.com/orange-pi-zero/

Clone this application: https://gitlab.com/cloud-oscilloscope/qtloscope
Compile it on your computer, load on armblian at sdcard and make it auto-loadable.

http://oscilloscope.cloud/

See how your oscillogram displayed on web-interface!