I have a chip that uses SPI for communication and would like to connect it directly to the USB port on my computer. Does anyone have experience with using a USB to SPI converter? How would I design a circuit to convert USB to SPI? http://www.robotshop.com/devantec-usb-i2c-spi-serial-interface.html
I draw a schematic and posted example code to run a chain of '595s off of a humble FTDI cable: How can I control 128 (or more) solenoids?
'595 are essentially SPI. The code bacomes a bit more complicated if you need to read data as well as write it. But it is still not bad.