|Min/max voltage||0V — 5V|
There's a best-effort driver to acquire raw samples from any FTDI chip supporting bitbang modes. As these chips have tiny I/O buffers, it doesn't guarantee overrun-free operation so it may lose samples, yet moving the device to a separate USB host or lowering the sample rate helps.
FT232RL and FT2232H are known to work, and adding an unsupported chip should be easy. Boards with the former are available on ebay for $3, but it doesn't support USB 2.0 hence sample rates will be lower. FT*H chips may provide ~20MHz sample rate over a reliable high speed USB link and (bursts of?) 60MHz using synchronous FIFO mode (not implemented in the sigrok driver).
This driver currently only supports FTDI chips configured in bitbang mode. This means you cannot use the driver with a board where an EEPROM configures the FTDI device to operate in a different mode. This means the driver doesn't work with Bitscope devices, for example.