[time-nuts] Are serial port headers standardized?

[Hal Murray]

kuzetsa at gmail.com said:
> Supposedly, normal serial ports have less trouble with latency than anything
> done over USB. I definitely have an annoying 590 (ish) millisecond delay
> when using the NMEA driver on my NTP daemon, ...

USB delays and jitter are on the order of 1 ms.

Things like 590 ms offsets are firmware bugs.  If they are constant, you can 
fix them by fudge-ing.  The ones I've seen have 100 ms of wander.  The rest 
is (mostly) constant.


[COM1 header]
> Are they fairly standard?

I'm pretty sure they are all setup so that a ribbon cable from a 10 pin 
header to a DE-9 will work correctly.

Beware: They also use a 10 pin header for getting 2xUSB to the front panel.  
There may be a missing pin on the USB and/or serial header that would allow a 
connector with a pin filled to not-fit on the wrong header.


> Will this work:
> http://www.newegg.com/Product/Product.aspx?Item=N82E16815158115

Looks good to me.  (But no promises.)  If I had that problem, I'd try 
something like that.

Note that there are 2 sizes of PCI brackets.  The old ones are about 4 inches 
tall.  The "low profile" ones are much shorter.


-- 
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