[ezschemi]

We recently built a product that utilizes FTDI chips for i2c/gpio/jtag/spi/swd-protocol support. My dev kits and bench setup uses the Adafruit FTDI breakout boards (https://www.adafruit.com/product/2264) to connect to various other circuitry. The driver and even the communication protocols are documented and open source (e.g. OpenOCD implemented their own based on the USB packets). The breakout board doesn't have 40-50 GPIO pins an RPI has, but you can hook multiple of these breakout boards to a computer. I am using 4 breakout boards with one ARM SBC each as targets, with no problems on an Intel NUC. And they are much smaller and easier to get than a RPi.

Besides the FT232H, there are larger FTDI chips with more channels. I am uncertain if one can find USB breakout boards for them, though.

[geokon]

oh that's really cool. What's the driver situation with something like that? On Linux do I just write to some file and it's mapped to some hardware pins? Or it's more complicated than that?