[Thumbgps-devel] USB handshake signals and Linux

[Eric S. Raymond]

Patrick Maupin <pmaupin at gmail.com>:
> The FTDI devices have a latency timer that allows you to control this
> somewhat.

I found a couple of hits on the search "PL2303 latency timer" that
implies it has one too.  But I doubt the value of the latency timer
will be relevant for handshake-line notifications; see below.

>       But even better, if we're going to use the PPS signal, they
> essentially guarantee that they will send ASAP on modem control signal
> change.  We might need to characterize "ASAP" but I would hope that it
> doesn't vary too much.

Probably not.  Trying to buffer a handshake state change doesn't make
any sense. I'm not surprised that the FTDI gives them realtime
priority and I *will* be surprised if the PL2303 (or any other
adapter) doesn't do likewise.  
-- 
		<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>