Using an UNO, this example sets up A0-A3 as the inputs for a very crude 4-channel logic analyzer.
SPI was set at 125kHz, single byte transferred.
Connect SCK, MOSI, MISO, SS to A0, A1, A2, A3.
Could work with I2C at 100kHz.
Results:
Serial_Plotter_Logic_Analyzer.ino (673 Bytes)