Uwe Bonnes wrote: > >>>>> "Thomas" == Thomas Jarosch <[email protected]> writes: > > ... > Thomas> Also you can focus on single tests only with this: > Thomas> "./test_libftdi --run_test=Baudrate/Type232HFixedBaudrates" > > Thomas> The output of the unit test is not that pretty as I put the > Thomas> actually testing in a generic function. Usually that's a no no, > Thomas> but I didn't want to duplicate the code for every chip > Thomas> type. Maybe a macro can come to the rescue here. > > The one basic is the description in the datasheet: > Baud Rate Generators - The Baud Rate Generators provides a x16 or a > x10 clock input to the UART's from a 120MHz reference clock and > consists of a 14 bit pre-scaler and 4 register bits which provide fine > tuning of the baud rate (used to divide by a number plus a fraction). This > determines the Baud Rate of the UART which is programmable from 183 baud to > 12 Mbaud. See FTDI application note AN_120 on the FTDI website for more > details. > > The other basic is how this bits get stuffed in the USB request. I didn't > find any documentation about it. AN_120 is not explicit. Have you more > information? > > I wrote the code with a strong look at the corresponding calculations in > /usr/src/linux/drivers/usb/serial/ftdi_sio.c and a test with the scope. For > the cases I tested, I saw somehow sensible results. However with the RS232 > pattern you can't easily measure exact frequency with the scope.
If you send a continuous string of UUUUU then you'll see the base frequency as a simple square wave. -jim > What are your doubts? A slight misscalcuation and bad rounding in my code or > values really far off the set value. The last case I can easily test with > the scope. Perhaps tell the setting that you expect a bigg error. It is > quite easy to test now with examples/serial. -- libftdi - see http://www.intra2net.com/en/developer/libftdi for details. To unsubscribe send a mail to [email protected]
