Totally agree with your FTDI comments however the simple USB-to-UART adapter doesn’t do it for me personally. I will buy cheap ones off of eBay and use them everywhere. (Just look closely to get the ones with activity LEDs. Love me some LEDs…). But FTDI is a hair expensive for that one usage.
Enter the FTDI C232HM cable!
For around $40 (USD) this thing does USB-to-UART out of the box. But additionally you can put it into a multiprotocol mode (MPSSE) and now the sky breaks open, the sun beams flare into beautiful ribbons of light as you observe that you now have JTAG, SPI, and I2C available to you! Oh, and GPIO bit-bang, if that doesn’t suit you.
Pair that cable with the PyFtdi library, well… NOW you’re cookin’.
I personally have used this as a normal USB-to-UART adapter and also used PyFtdi + PySpiFlash (both written by Emmanuel Blot) to program an FPGA’s flash chip. Not at the same time of course, it’s fancy, but not that fancy.
Cable is available in 3.3v and 5v options so take your pick.
And no, I’m not affiliated with FTDI, lol.