FT232H with MCP3204/01 ADC
In my earlier articles, I described Hardware Interactive Development (HID) with FTDI devices (FT232H or FT2232H) running in MPSSE mode. It skips the MCU (for example, Arduino) in between, and goes directly from PC to the hardware pieces for prototyping.
In its MPSSE mode, FT232H device is capable of both SPI and I2C protocols, in addition to its usual digital IO toggling. That should covers a lot of grounds where MCUs like Arduino stand.
The only thing missing is to read ADC input.
Fortunately, there are plenty of off-the-shelf ADC parts that talks SPI or I2C, for example MCP3204 is a SPI-able ADC with good sampling rate (50ksps).
Here is the gist of reading analog voltages from MCP3024 channels via SPI.