USB 1.0/Low-Speed: 1.5 Mbps USB 1.1/Full-Speed: 12 Mbps. USB 2.0/Hi-Speed: 480 Mbps. USB 3.0/SuperSpeed: 5 Gbps. USB 3.1/SuperSpeed: 10 Gbps. This is the actual bitrate for these serial interfaces.
Bill On Wed, Jul 8, 2020, 5:16 PM jimlux <jim...@earthlink.net> wrote: > On 7/8/20 4:40 PM, Hal Murray wrote: > > > > stevesommars...@gmail.com said: > >> My RPi4 (Raspbian Buster) has a GPS+PPS/USB. Serial->USB uses Prolific > >> PL2303, which supports USB 2.0 > > > >> which means 1 msec polling of the PPS signal. I've been unable to > poll more > >> frequently > > > > As far as I know, the PL2303, 067b:2303, is an old/slow chip. (I forget > the > > right magic USB terms) Why do you expect it to go faster than 1 ms? > > > The underlying frame rate on USB (even the slowest USB1.0) is 8kHz, so > it's not unreasonable to expect that a chip might be able to "poll" a > status signal at that rate. > > > > > > It and the FTDI chip(s) are popular and widely known to be well > supported on > > Linux. I'll be very surprised if it goes faster. > > There is that. OTOH, drivers do get updated. One could probably, if you > were hard core, look at the device driver code in the Linux distro and > figure it out. > > > > > > What sort of device are you using? One way to tell if it is likely to go > > faster than 1 ms is the thickness of the wire. Faster speeds need more > > shielding for EMI reduction (or something like that) which turns into > fatter > > cables. It's pretty easy to tell if you have samples of both in front > of you. > > I think you can only use the thinner cable if t runs at 1 ms and you > hard > > wire the chip to the end of the cable as is typical of a GPS mouse. > > > > > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.