[time-nuts] GPS USB dongle for time server

[jimlux]

jim s wrote:
> This is probably the thousandth time this was asked, but I googled and 
> didn't get a direct answer.
> 
> I want to do a crude (as in to the second or so) time server inhouse to 
> add into a group of high accuracy servers.  This is so that I can go off 
> grid and still get updates.
> 
> I see that there is a way to get a feed called PPS or with PPS via 
> RS232.  The discussions of using USB instead are concerned with having 
> too much jitter.
> 
> since USB by its nature won't have an accurate exact dedicated line to 
> let the GPS toggle to do a time hack to the software, I can see why 
> RS232 is preferable with the hardware signal lines they have.
> 
> If I just go with the NEMA stream as it gets to me via an USB HID Com 
> port, I assume that there will be some jitter baring a way to send in 
> the physical time hack.
> 
> 

I would think that USB is not inherently worse than a hardware RS232. 
Both have some interrupt latency, but it's small in both cases.  USB has 
to handle audio reliably at no worse than 8kHz sampling rate.