[Thumbgps-devel] USB handshake signals and Linux

[Patrick Maupin]

On Wed, Mar 14, 2012 at 1:57 PM, Dave Taht <dave.taht at gmail.com> wrote:

> In a private chat late last night andrew mentioned that the ftdi devices
> were extensively reprogrammable, in that they came as a usb device
> but were really, underneath, just a bunch of gpios...

Yes and no.  The bandwidth associated with using them as GPIOs is
relatively high compared to using them for serial ports.  They have a
lot of logic to support serial communication and also (in some cases
-- not all devices have this) some other modes like SPI, I2C, JTAG, or
CPU bus emulation.

I have personally used them in serial, parallel FIFO (a fast serial
emulation), GPIO, and JTAG modes.