FADC Data Format November 25, 2014

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Location and Time

Room: CC F228

Time: POSTPONED to 3pm because there's a run meeting at 2pm.

Remote Connection

(if problems, call phone in conference room: 757-269-6460 might not be the correct number)

  1. To join via Polycom room system go to the IP Address: (bjn.vc) and enter the meeting ID: 589693655.
  2. To join via a Web Browser, go to the page [1] https://bluejeans.com/589693655.
  3. To join via phone, use one of the following numbers and the Conference ID: 589693655
    • US or Canada: +1 408 740 7256 or
    • US or Canada: +1 888 240 2560

More information on connecting to bluejeans is here

Specific instructions for connecting via polycom:

  • Turn polycom on if necessary
  • With the polycom, place a call at
  • Press # to enable the polycom keypad, then enter the meeting id: 589693655 and #
  • You may have to unmute the microphone: #*4
  • Turn the computer on if needed


Useful Links


Present: Naomi (CMU), Cody, David (JLab)

  1. Cody has made good progress on integrating the CDC timing algorithm into the fa250 firmware. He now has it interfacing with the raw window buffer, calculating time and mini-integral (the first part of the integral, between the leading edge time and the initial threshold crossing time) and combining the mini-integral with the remainder of the pulse integral (from the initial threshold crossing to the end of the integration time). It is producing our two-word readout although the format needs a little tidying; in simulation it looks fine.
  2. Next Cody is intending to rewrite some of the firmware architecture which was required for the fa250 but is not necessary for the fa125, this will make data access much quicker as the data addresses will be available instantly instead of being registered (stored into a register at the end of a clock cycle, and cannot be retrieved until the next clock cycle). Much of the state machine will no longer be required and cleaning this out will make the firmware much easier to work with as well as taking less clock cycles to run. He plans to make a trimmed-down state machine for the two-word CDC readout format and then extend this to create the other data formats.
  3. Cody asked about the fa250 parameter NP, how many pulses do we wish to read out from one trigger window. For the CDC we just need one, the FDC would like more than one. So it would be best to leave this as a configurable parameter, as with the fa250.
  4. Cody also asked about the likely range of pedestal width 2**N required. Again, leave this as a configurable parameter.
  5. Naomi has been using a C++ translation of the CDC algorithm to examine some of the recent run files, using the DAQTree plugin to extract the window raw data. This uncovered a bug (8 events out of 2,353,000) which seems to be associated with fadc readout errors, the algorithm had assumed that the upsampled data matched the sampled data, but if there are discontinuities in the fadc data then the upsampled data are not so accurate. (see wiki page) In any case, this is easy to fix.