[time-nuts] Pendulum CNT91 with TimeLab

[GandalfG8 at aol.com]

Hi John
 
I can assure you that "helped" is very much an understatement:-), and again 
 many thanks.
 
Thanks too for your comments re talk-only vs native drivers, I  understand 
better now and will keep those archived for future reference.
 
There's certainly a lot less incentive now to further  investigate where 
I'm going wrong with the CNT91 talk-only configuration,  I'm assuming it's me 
rather than the counter anyway:-), but if I do ever get it  sorted I will 
certainly report back.
 
Regards
 
Nigel
GM8PZR
 
 
 
 
 
 
 
 
 
 
 
 
 
In a message dated 10/10/2013 20:05:21 GMT Daylight Time, john at miles.io  
writes:

Good to  hear the modified driver helped -- thanks for the confirmation!
I'll leave  that option in the code for future releases.

There's no compelling  reason to use the generic talk-only driver with a
counter that is also  supported by a native talk/listen driver, as long as
the latter works  reliably.  The native drivers don't do much to configure
the counter,  but they can do one or two helpful things such as ensuring 
that
certain  statistical features that would interfere with the measurement are
turned  off.  They also allow the counter to reside on a GPIB segment  
that's
shared with other addressable devices, which is problematic in  talk-only
mode.

The trouble with the native drivers arises from the  fact that the only TIC 
I
have around here is the HP 5370B, which doesn't  use the same driver code as
the SCPI-era models like the 5313xA, SR620,  DTS207x, etc.   So when I make 
a
change that affects those  drivers, it's always going to be a "Customer as
Beta Tester"  scenario.  And we all know how well untested code  usually
works.

The need to support Prologix USB, Prologix Ethernet,  and NI 488.2 adapters
complicates matters further because their low-level  behavior, timing
characteristics, and driver interfaces couldn't be more  different from each
other.  Add in the notion of counters like the  Pendulum that are
almost-but-not-quite compatible with supported models,  and the fact that
even the native TimeLab drivers still rely on the user to  set up the
measurement parameters, and you get a pretty intimidating matrix  of
conditions that are realistically never going to get tested until  someone
tries to use them. 

The talk-only driver simplifies the  picture because I can test it with the
5370B just by flipping a DIP switch  and verifying that it works with the
three supported GPIB adapter  types.  It doesn't rely on issuing
device-specific trigger and read  commands to counters I don't own.
Talk-only measurements are still not 100%  reliable due to occasional
weirdnesses in the GPIB adapter or counter  firmware, but those aren't my
fault. :)

Basically, just use  whichever driver works most reliably in your particular
situation, and keep  the reports coming so we all know what works and what
doesn't. 

--  john, KE5FX
Miles Design LLC 


> Hi John
> 
> Just  as a quick follow up, I'm still intrigued as to why I've been
>  seemingly unable to get the CNT91/FCA3100 to run in talk-only mode and
>  might  well
> come back to that when I have a bit more time but,  from a TimeLab point 
of
> view, with the HP emulation up and running  would there actually be
> anything
> to be gained by doing  so?
> 
> Regards
> 
> Nigel
>  GM8PZR

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