FTDI has created a truly remarkable chip,
the FT232RL. Its about the fastest possible
way to get a PIC connected to USB2.0. I just
finished a design with it and it  is worth talking
about:

The FT232RL is like the FT232BM in its overall
function- USB to serial conversion-. but after
that, it is a new ballgame. Here's some of the
improvements:

1. TSSOP28 package. Its actually smaller than
the original FT232BM footprint, and is available
in a QFN package, too, for the masochists among
us.

2. NO crystal required! Yes, folks, it has a precise
internal oscillator that generates its internal 48Mhz
clock and synchs its clock to the USB buss when it
is attached. Moreover, that internal oscillator can be
brought out as 24, 12, or 6 Mhz (or all 3!).

3. Internal unique serial number, readable by the
PC USB port attached to the chip. Allows creating
reliable product ID systems and/or software upgrade
methods..

4. All common baud rates, and many custom ones as
well! This means that the thruput can be dramatically
increased by setting the baud rate at 250Kb on the
PIC and setting the same on the FT232RL. The chip
has an internal 384-byte FIFO buffer, so using hardware
flow control, you can  move the data.

5. Programmable pins in almost every conceivable
combination, inverted TX/RX/DSR etc, and even bit-
bang modes (now 3 unique modes). Pin drive can be
normal 4mA or high 12mA outputs.

6. Programmable EEPROM space to allow you to
fully identify your product, to ease driver installation.

Take a look at:

http://www.ftdichip.com/Products/FT232R.htm .


--Bob   

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