On Thu, Apr 2, 2009 at 8:43 PM, Thomas Jarosch <[email protected]> wrote: > Hello Florian, > > Florian Beier wrote: >> >> Hi again, >> I managed to use the libftdi without the D2xx commands to communicate >> with my sensor. >> I have on issue, I do not understand. >> I am checking the buffer of my FT2232 chip. If it is empty, the >> usb_bulk_read in the ftdi_read_data function takes almost 12 ms. If >> the buffer has data, it only takes about 1 ms. >> I tried to change the ftdi->usb_read_timeout, but it had no effect at all. >> Any ideas? > > Sounds like the on-chip latency timer, try to decrease it via > ftdi_set_latency_timer().
Thanks, Thomas. To be honest, I am not sure, what I changed, but my ftdi_read_data times are down to approx. 1ms (independently from thich ftdi_set_latency_time I use) Actually I do not understand, what the set_latency_timer does. I thougth the ftdi_read_data would "wait" the given latency time, till something is in the buffer. But even if I do set the latency to 255, and nothing is in the buffer, the READ returns in 1-2ms. What is the unit of the param latency? My second question is: Does anyone know why an FT_Read with FT's D2XX lib does return so fast? (I measured approx. 0.01ms compared to my 1ms with the ftdi_read_data.) Thanks for any help! Florian -- libftdi - see http://www.intra2net.com/en/developer/libftdi for details. To unsubscribe send a mail to [email protected]
