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Hi Beni,<br>
<br>
How do we adjust where the pedestals are? I can imagine a software
offset in the FPGA, but that won't fix<br>
a negative DC offset. Do the modules have the capability of setting
this via VME? (My experience with old<br>
modules was using a small screwdriver, but that can work here!)<br>
<br>
Regards,<br>
-David<br>
<br>
<div class="moz-cite-prefix">On 7/24/13 9:14 AM, Beni Zihlmann
wrote:<br>
</div>
<blockquote cite="mid:51EFD323.7030201@jlab.org" type="cite">
<meta content="text/html; charset=ISO-8859-1"
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<div class="moz-cite-prefix">Hi Naomi, everybody, <br>
<br>
I finally looked through all the back and forth on this issue
and more or less understand<br>
the last iteration of the data format. So here my 0.5 cent
blabla:<br>
<br>
0) As you point out the pedestal position/width changes if a
cable is connected to the ADC or not and<br>
also where the cable is coming from (pream source) because
all this matters to the overall ground<br>
and capacitive coupling that is seen by the ADC channel.<br>
that is why we need to monitor the pedestal at all times and
needs to be in the data.<br>
<br>
1) 12 Bits for the pedestal is overkill. As you write below we
want to have the pedestal as reasonably<br>
low as possible to maximise the dynamic range of the ADC.
An offset of 0x8000 puts that pedestal<br>
roughly in the middle of the full range of the ADC but
there is quite a large variation from channel <br>
to channel. In the FDCs I observe base lines easily vary
between 2500 and 5000 or even more.<br>
(note these numbers are with the traditional factor 4 ! ;-)
)<br>
The offsets should be set such (for each individual
channel) that it is sufficiently high above zero to<br>
accommodate the noise. This means it has to depend on the
width of the pedestal (noise), lets say<br>
for the sake of argument an offset above zero is 4 sigma of
the pedestal. I can not remember what <br>
the answer was to the question "what happens to the ADC
when the input signal undershoots the<br>
low edge of the dynamic range?"<br>
Note that the pedestal is normalized to one sample.<br>
From this considerations the pedestals in the proposed data
format can easily be expressed with 8 bits.<br>
<br>
2) we do not need special pedestal runs, what we need is special
runs reading out all samples with the offsets<br>
all set at 0x8000 or some other most preferred offset. From
that data one can easily calculate the pedestals<br>
and width and from that new best offsets. These new offsets
can then be loaded and the procedure repeated<br>
to verify/optimize the settings if so desired.<br>
-> which of course brings up another point of
book-keeping these pedestals, width and offsets and what is<br>
currently loaded in the ADCs.<br>
<br>
<br>
3) I think it is a very bad idea to have different data formats
for the FDC and CDC. We have to come up with<br>
a common solution. The threat of a potential mix-up in the
future overweights any benefit I see.<br>
<br>
4) The next very important step is now to understand what
algorithms we want to implement to determine<br>
pedestal, integral and time. I guess this is the harder
part. We have to specify what we want and find<br>
out what we can get ;-) (We can't always get what we want
but we can try). <br>
-> I propose for the next tracking meeting to have a
discussion of what we want. We should try to start<br>
with the basics (simple approach with expansion in
mind) and then go from there to see how far we <br>
can push the system.<br>
<br>
<br>
cheers,<br>
Beni<br>
<br>
<br>
<br>
<br>
<br>
<br>
</div>
<blockquote
cite="mid:C970103D-3CFB-4DEE-91B4-6BABFB9CA236@cmu.edu"
type="cite">
<div>Hello, </div>
<div><br>
</div>
<div>OK.</div>
<div><br class="webkit-block-placeholder">
</div>
<div>Yes using all 12 bits would indicate a huge problem,
pedestal should really be in a much smaller range such as
between 40 and 80, could be higher if on the tail end of a
previous event. If it moves (and stays) outside that range
you need to know where it is in order to correct the offset on
the flash. I am finding that the pedestals change when I
switch electronics or read out a different set of straws.
Also the pedestal rises (and gain falls) if the preamp LV
supply drops, which is a good indicator of a bad cable at the
HVB end. So we would need full range readout at least for
setting the pedestals following maintenance and for periodic
monitoring; this could be done using a dedicated pedestal data
format rather than in the pulse data format.</div>
<div><br>
</div>
<div>Naomi.</div>
<div><br class="webkit-block-placeholder">
</div>
<div><br class="webkit-block-placeholder">
</div>
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<br>
<div>
<div>On Jul 23, 2013, at 11:08 AM, David Lawrence wrote:</div>
<br class="Apple-interchange-newline">
<blockquote type="cite">
<meta content="text/html; charset=ISO-8859-1"
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<div bgcolor="#FFFFFF" text="#000000"> Hi All,<br>
<br>
To answer your last question first: Yes, the crate
number (rocid) is included in an EVIO header that is put
on by the ROC before the data is sent over the network.
The ROC may send more than one "Physics Event Bank" for a
block of events (e.g. multiple DMAs are used), but the
number will generally appear just once or twice for all
hits in all events in the block.<br>
<br>
As for the pedestal, wouldn't this indicate a problem if
the pedestal itself was a large enough number as to
require 12 bits? I thought from earlier discussions we
were going to try and adjust the pedestal so that it was
never larger than say, a 9 -bit number could hold (0-511).
This would leave 6 bits for the Q.F. Not that I'm
completely opposed to dropping the slot from the hit data,
but I do like how it is currently being used to help check
the data integrity in a stream-like fashion which helps
supplement the other checks being done with larger data
chunks.<br>
<br>
Regards,<br>
-David<br>
<br>
<div class="moz-cite-prefix">On 7/23/13 10:43 AM, Naomi
Jarvis wrote:<br>
</div>
<blockquote
cite="mid:863CB2AD-C6DA-46FB-94DD-827FA6A48951@cmu.edu"
type="cite">
<div><span class="Apple-style-span"
style="border-collapse: separate; font-family:
Helvetica; font-style: normal; font-variant: normal;
font-weight: normal; letter-spacing: normal;
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none; white-space: normal; widows: 2; word-spacing:
0px; -webkit-border-horizontal-spacing: 0px;
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-webkit-text-decorations-in-effect: none;
-webkit-text-size-adjust: auto;
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class="Apple-style-span" style="border-collapse:
separate; font-family: Helvetica; font-style:
normal; font-variant: normal; font-weight: normal;
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">
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after-white-space; "><span
class="Apple-style-span"
style="border-collapse: separate; font-family:
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<div style="word-wrap: break-word;
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-webkit-line-break: after-white-space; ">
<div>Hi Gerard,</div>
</div>
</span><br class="Apple-interchange-newline">
</div>
</span>David put together a draft document for the
current spec - <a moz-do-not-send="true"
href="http://argus.phys.uregina.ca/cgi-bin/private/DocDB/ShowDocument?docid=2274">http://argus.phys.uregina.ca/cgi-bin/private/DocDB/ShowDocument?docid=2274</a><br
class="Apple-interchange-newline">
</span><br class="Apple-interchange-newline">
</div>
<div>There the slot does come before the channel, and we
have one large 15-bit chunk designated as quality
factor which would include the pedestal.</div>
<div>I hadn't realized that the slot would also be in
the block header. </div>
<div><br>
</div>
<div>Could we take some of the 5 bits marked slot and
move them into the QF section? The extra space (QF
would then be 20 bits) would allow for full precision
pedestal in 12 bits, plus another 8 for quality
indicators. Also, we have 3 bits in the block header
to designate data format, or rather, how to interpret
the QF part. I would hope that we would not go
through more than 8 iterations of this but it could
happen, and 1 or 2 bits of the QF section could be
kept aside for this. If we have full precision
pedestal in the event readout then I don't think we
would need separate pedestal runs. </div>
<div><br>
</div>
<div>(Is there another header designating the crate
which is tagged on separately?)</div>
<div><br>
</div>
<div>Best, </div>
<div><br>
</div>
<div>Naomi.</div>
<div><br>
</div>
<div><br>
</div>
<div><br class="webkit-block-placeholder">
</div>
<br>
<div>
<div>On Jul 23, 2013, at 9:58 AM, Gerard Visser wrote:</div>
<br class="Apple-interchange-newline">
<blockquote type="cite">
<div>hi Dave,<br>
<span class="Apple-tab-span"
style="white-space:pre"> </span>I think it
might be better to provide a more generic and
all-encompassing <br>
redundancy in the data, such as by inserting a CRC
word every N hits or at end <br>
of block or something like that. Just a fixed
pattern on a few bits is a pretty <br>
minimalist sort of redundancy, e.g. would not
detect if an even number of <br>
longwords was dropped, for instance.<br>
<span class="Apple-tab-span"
style="white-space:pre"> </span>I also suspect
that more bits might be good for quality/status of
the hit, <br>
although I don't have a specific proposal. At the
moment I see it is proposed <br>
(1c) to have 13 bits for "pedestal"&quality
(these are all quality bits IMHO). <br>
This may eventually prove not to be enough, then
the 5 slot bits could be added <br>
into this purpose.<br>
<span class="Apple-tab-span"
style="white-space:pre"> </span>Regardless of
the slot bits, I think you are certainly right to
put some <br>
redundancy in the data that can be used for
integrity check, so IMHO you should <br>
add some CRC words explicitly for that purpose.<br>
<span class="Apple-tab-span"
style="white-space:pre"> </span>Sincerely,<br>
<br>
<span class="Apple-tab-span"
style="white-space:pre"> </span><span
class="Apple-tab-span" style="white-space:pre">
</span>Gerard<br>
<br>
p.s. Minor point: If you do keep slot field, how
about putting it to the left of <br>
channel field, so that the whole thing can be
interpreted as a 12 bit <br>
superchannel number? Of course the bit arrangement
doesn't matter except to <br>
improve human readability of the code and data.<br>
<br>
<br>
On 7/23/2013 1:14 AM, David Lawrence wrote:<br>
<blockquote type="cite"><br>
</blockquote>
<blockquote type="cite">Hi Gerard,<br>
</blockquote>
<blockquote type="cite"><br>
</blockquote>
<blockquote type="cite"> That's correct, "slot"
is the slot in the VME crate. You're right, it<br>
</blockquote>
<blockquote type="cite">could be sacrificed from
the hit record if needed. Right now, it appears<br>
</blockquote>
<blockquote type="cite">in the both the block
header and hit record and is currently used by
the<br>
</blockquote>
<blockquote type="cite">parsing software to
provide a small integrity check on the data. If<br>
</blockquote>
<blockquote type="cite">there is something else
more worthy of those bits, we can consider<br>
</blockquote>
<blockquote type="cite">dropping it from the hit
record.<br>
</blockquote>
<blockquote type="cite"><br>
</blockquote>
<blockquote type="cite">Regards,<br>
</blockquote>
<blockquote type="cite">-Dave<br>
</blockquote>
<blockquote type="cite"><br>
</blockquote>
<blockquote type="cite">On 7/23/13 12:47 AM,
Gerard Visser wrote:<br>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">hi Naomi, Dave,<br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite"><span
class="Apple-tab-span"
style="white-space:pre"> </span>What is
'slot' by the way? (5/62 hit payload bits used
for this.) I guess it is<br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">the ADC module number?
But why put this in the hit record? It can
just as well<br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">be in the block or event
header from the module, it will be constant
for all hit<br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">records from the
module...<br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite"><br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite"><span
class="Apple-tab-span"
style="white-space:pre"> </span>- Gerard<br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite"><br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite"><br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">On 7/22/2013 7:58 PM,
Naomi Jarvis wrote:<br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite">Minutes are online at
<a moz-do-not-send="true"
href="https://halldweb1.jlab.org/wiki/index.php/July_17,_2013_Tracking_CDC/FDC">https://halldweb1.jlab.org/wiki/index.php/July_17,_2013_Tracking_CDC/FDC</a><br>
</blockquote>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite"><br>
</blockquote>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite">Also I think I forgot
to email the same for the previous meeting,
sorry, those are at <a
moz-do-not-send="true"
href="https://halldweb1.jlab.org/wiki/index.php/July_3,_2013_Tracking_CDC/FDC">https://halldweb1.jlab.org/wiki/index.php/July_3,_2013_Tracking_CDC/FDC</a><br>
</blockquote>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite"><br>
</blockquote>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite">Best regards,<br>
</blockquote>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite"><br>
</blockquote>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite">Naomi.<br>
</blockquote>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">_______________________________________________<br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">Halld-tracking-hw
mailing list<br>
</blockquote>
</blockquote>
<blockquote type="cite">
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