[time-nuts] Thunderbolt and USB to RS232 converters

Didier Juges didier at cox.net
Wed Jun 25 20:19:40 EDT 2008


I have two Prolific adapters on a single hub, which is probably low speed
(it was cheap). They work fine under XP, even though one of them is used
with a program (development system) that has shown some finicky behavior
when driving a serial input JTAG box with the old drivers. The other one
drives my ham radio's serial port. The Thunderbolt is normally plugged into
the hardware serial port COM 1 on this machine, I will try with the Prolific
adapter just for grins.

Didier KO4BB

> -----Original Message-----
> From: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Hal Murray
> Sent: Wednesday, June 25, 2008 7:03 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Thunderbolt and USB to RS232 converters
> > That's a good point. The older Prolific drivers had a nasty 
> habit of 
> > crashing my laptop (Win XP would not wake up) if I put it in 
> > hibernation with the adapter plugged into the USB socket. The new 
> > drivers mostly fix the problem. I may occasionaly have to 
> unplug and 
> > replug the device after waking up, but the OS no longer crashes.
> The SIRF GPS units use the Prolific chips.
> I have had mixed results with them on Linux.
> They don't work like I expect when I try to use several of 
> them on a high speed hub.  The Prolific chip wants some 
> guaranteed bandwidth and Linux has troubles allocating it.  I 
> thought I found a kernel option to get around that, 
> CONFIG_USB_EHCI_TT_NEWSCHED, but I tried to clean things up 
> last night and mumble.  I guess it helps but not as much as I 
> though.  Mumble.  It may be the hub-hub case that doesn't 
> work.  I've got a 7 port hub which is really
> 2 4 port hubs chained.
> I haven't noticed any troubles without the hub.  I'm not 
> doing anything fancy.

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