See the top level README for information on where to find the schematic and programmers reference manual for the ARM processor on the raspberry pi. Okay this was incredibly painful. I might have saved a few hours if was at the office with an oscilloscope, I eventually had to fashion something to look at the output using an mbed. The documentation for the chip has some glaring errors. The IER and IIR register descriptions are screwy. The one that killed me was the word length. The document says that the single bit controls 7 bits per word vs 8 bits per word. And that bit 1 and some above do not do anything, they might on real 16550's but not here. Well that is wrong. If bits 1:0 are 00 you get 7 bits if bits 1:0 are 01 you get 7 bits. You need bit 1 set to get 8 bits. This example uses the mini uart, uart1, to transmit characters on GPIO14. You will need a level shifter or something that can receive 3.3v. One like this http://www.sparkfun.com/products/718 works perfectly. Connect ground to pin 6 of P1 and rx on the FTDI board to tx on the raspi which is pin 8 on the P1 connector. This example sets up the uart for 115200 baud, and blasts the characters 0123456701234567...forever as fast as it can.