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• Axilon will install in FEE in December
• Georgi wants it in DAQ by end of 2023
• Quadrature output, oversample counter at 186MHz, sample that at 1MHz
• front-end board (not a computer) KCU105 receiving (like wave8)
• need to order now (16-week lead time)
• should ask hard x-ray hutches if they want any of these
• does TID need a test encoder?  they think it's ok to use an oscilloscope to capture a few ticks of the encoder (May Ling wants to do this anyhow to test connections)
• this encoder will be in the FEE, so not always accessible
• will absolute encoder plus interpolation be as good as the high rate relative encoder?  answer: we will have to look at the photon "energy resolution".
• Can the absolute encoder go to higher rates?  Zach writes:

  "With an alternate hardware configuration, the absolute encoder can run faster than we currently run it, but it cannot ever get close to 1MHz.

  So, if the goal is to measure the position at full beam rate, we definitely need the alternate encoder hardware as planned.

  The BiSS-C protocol allows a maximum clock rate of 10MHz, and this is theoretically the maximum data rate in bits. The full position is sent with every BiSS-C cycle. Therefore, we'd need to allocate less than 10 bits per position to have a chance at hitting 1MHz. In practice there are >40 bits per position including status bits, error bits, and checksums. There is also some additional mandatory dead time. There are some documented tests on the internet of running these sorts of encoders up to 33kHz or so, but nothing near the 1MHz mark."

Meeting on Dec. 12, 2022

An email message I sent after the meeting:

- Ken Lauer wrote that AD has some ATCA firmware for reading relative encoders out which may help.  Ken: can you tell us a name we could contact about that?
- Alex (or someone in his group) is going to measure voltage waveforms from the encoder this Friday and will send to you
- I think we’re leaning towards putting the TID box in the FEE, close to where the encoder is.  Alex recommended Mike Estrada as a person who could allocate that rack space for you.  Can you tell us a guess for how many rack spaces you need so Mike can allocate?

Also, we need to patch two fiber pairs (timing, data) to the TID device in the FEE, ideally to room 208 or the FEE alcove.  Jana (or anyone else): do you know if there are two fiber pairs available to us for this, or if we should get something strung?

Encoder Simulator

Chris Ford has an encoder simulator in lab3, with documentation here:  UDP Encoder Interface (rix Mono Encoder).  He also has committed lab3-caf-encoder.cnf to lcls2 GitHub in psdaq/psdaq/cnf/

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