[LinuxPPS] any hardware folks out there?

[Remco dB]

a) Perhaps you have an 'earth loop'? 
Check whether your grounding is ok. I.e. how you feed (power supply) the 
Oncore and or check whether you use the same power supply groups in your 
shack (i.e. here in Europe the groups offered to houses are divided between 
the three phases of 380 VAC and, when your neighbour, or someone else in the 
street, has a different power consumption, the three phases are 'not in 
phase' (i.e. don't null out) , relative to the 'ground').

My advice, feed the Oncore with the same +5V within your computer (red wire 
on your 'hard disk' connector) and use the same ground (i.e. black wire). 

b) Perhaps you have an earthing problem. Do not know whether you use
115VAC of 230VAC (with 'earthing/ground') and whether the earthing is 
connected to the computer case?

In both cases (a part of) the VAC power supply _may_ be super imposed on 
the GND, and in the most severe case causing a 'ground', shaking with the 
amplitude of your VAC used. 

Check the (mostly metallic) case of the computer and check whether it makes
a connection with pin5 of your RS232 connector. 

Check the antenna cable ground relative to your RS232 lines. Perhaps the 
antenna ground makes a connection with 'another ground' or something else?

When you measure (DC of AC) voltages between several 'groundings', something 
is wrong.

When the grounding is ok, a normal RS232 port will accept TTL levels, 
especially when there's an 'active zero'. 



On Monday 22 December 2008 21:03:46 Reg Clemens wrote:
> Ive had some strange behaviour on my main machine here over the last
> month/6weeks
> and perhaps someone can give me a clue as to whats going on.
>
> Ive been running ntp on this machine forever (its a 3.2GHz Pentium).
>
> About 6weeks ago, linuxPPS/ntpd stopped working,- there was no pps signal.
> Yet plugging the same ONCORE into the next machine down was fine.
> So there was signal on the line, the machine was not seeing it.
>
> After puzzling this for a couple of weeks, I decided the simplest solution
> was to buy a new tty card,- mabe something REALLY had gone bad in the tty
> circuit on this motherboard.
>
> So I got a new 4 port board, and everything was fine for a couple of weeks
> and then PPS died there too...  OK thats too much of a coincidence.
> I plugged into a different port on the 4port board and everything was fine.
> Went back to the original port and its fine again too.
>
> I have yet to try the port on the motherboard.
>
> Ive used linuxPPS with and with out IRQ support during this time,
> and Ive been testing 64bit linux, tho I run 32bit 99% of the time.
>
> So any thoughts on why I would NOT see PPS signals on DCD, and then
> magically have them reappear.   Cabling DOES seem to be ok, since I
> tried a separate cable from the 2nd port on the Tac2/ONCORE, with
> the same negative results.
>
> Im just puzzled (and expect the problem to reappear) and hoping for
> some brilliant thought on whats going on...