[Dsg-hallc_nps] [EXTERNAL] Re: 5 additional CAEN HV cards -- LED driver board Notes

[Brad Sawatzky]

Timeline for the remaining HV card checks sounds fine.  Thanks very
much -- that DSG Note is great.

Here is a summary off the top of my head:

The 'LED driver' system will be composed of 7--10 JLab designed
FPGA-based VME boards in a single crate.  The boards will be
controlled/accessed through a VME single-board computer running linux.
Generally the FE group supplies a C library for low-level access to the
registers.  The boards will be able to individually control an LED
integrated into each of the 1080 crystal+pmt assemblies.

I'm attaching a Draft write up by William Gu that describes the board
and the functionality.  There are two general modes of operation:
A)  'Bleaching Mode'
    - LEDs are turned on at 'max power' and stay on for up to several
      days to anneal out radiation damage in the detector crystals.
    - Fairly straight forward - basically an 'All ON / All OFF' switch,
      perhaps with a timer and logging mechanism.
    - I would expect this to share the same interface as (B), but
      would simply involve an extra 'Bleach' button that would engage
      all of the LEDS flagged 'active'.

B)  'Pulsed Mode'
    - Any subset of the LEDs will be able to driven by a (short) pulse
      that will induce a signal in the PMT that approximates a true
      particle interaction.

    - Ideally the GUI should provide a few basic options: 
      - a pulse-duration field,
      - a pulse-amplitude field (common to all LEDs),
      - a pulse-frequency field (common to all 'active' LEDs),
      - 'Select all / Disable all',
      - indicate what LEDs are 'active' in graphical 2d representation
        of the 30x36 detector array, and
      - being able to click and/or drag-select groups of crystals in
        that 2D grid.  For example, similar to how one would select
        cells in a spreadsheet. I am hoping(!) this is general enough
        that a 'grid' widget is present in your favored GUI toolkit that
        can support this.

Additional features that would be useful would include
    - An 'import/export' feature to save a configuration and/or restore
      a configuration.
    - A 'logging' hook that would run a script when used to generate a
      logbook entry when the 'Bleach' or 'Pulse Now' button.


It is likely that a CODA ROC process running on the same single-board
VME computer will also access the boards through the VME interface.
We will have to be mindful of race conditions and appropriate locking.
This is something that the FE group will handle in their C library, but
the GUI should perhaps poll the boards periodically and update its
GUI if there has been a configuration change, for example.


Regarding timeline:

My understanding is that the FE group has ordered a prototype board that
should be arriving in 4--6 weeks.

William will need to spend some time testing the board, playing with
the firmware, etc.  Once that is basically final (ie. the software
interface is nailed down), then we (William, you folks, and me)
should meet and discuss details.  Somewhere in there William (or the FE
group) will develop the C driver library as well.

A rough timescale for a fully-fledged GUI could be June/July, perhaps?

There will be a lot of expert-driven stuff we can do by poking at
registers on the command line, so we will not need a full GUI right
away.


Hope this helps -- save it in a 'notes' file for future discussions.

-- Brad


On Tue, 16 Feb 2021, Aaron Brown wrote:

> Hi Brad,
>
> In our weekly DSG-NPS R&D meeting today we discussed testing the
> additional modules you dropped off.
>
> Tomorrow we will start running the full battery of tests (voltage and
> current stability, ramp, and trip) on the five A7435SN modules and the
> four A1535 modules that you dropped off back in September.
>
> This should all take 2 to 2.5 weeks.

> Also, during the collaboration meeting it was mentioned that DSG would
> make the control and monitoring GUI for the LEDs.

> Would you happen to have any information about this?
> Thanks,
> Aaron

-- 
Brad Sawatzky, PhD <brads at jlab.org>  -<>-  Jefferson Lab / Hall C / C111
Ph: 757-269-5947  -<>-  Fax: 757-269-5235  -<>- Pager: brads-page at jlab.org
The most exciting phrase to hear in science, the one that heralds new
  discoveries, is not "Eureka!" but "That's funny..."   -- Isaac Asimov
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