I have a Raspberry Pi Zero Wireless and I wish to connect it to an FPGA via SPI. I have done some SPI tests with my 100 MHz oscilloscope and see the images shown below. The Raspberry Pi correctly outputs the text "Test" using a simple C program.
The SPI is running at 1 MHz. The waveforms do not look very clean, and I am wondering why. They are not clean on the rise and fall points. I am using hookup wire to connect to the GPIO Pins. Ultimately, I wish to make this much faster than 1 MHz. Why are there spikes in the waveforms?
I am not using any pull up or pull down resistors. Should I? The wires are simply connected to the GPIO header. The chip select line (yellow) has some anomalies that I wish to get rid of/learn about.