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ZEBRA - PowerPoint PPT Presentation


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ZEBRA. Tom Cobb. What is a zebra?. Zebras ( /ˈzɛbrə/ ZEB -rə or /ˈziːbrə/ ZEE -brə ) [1] are several species of African equids (horse family) united by their distinctive black and white stripes. What is ZEBRA?. A digital signal level converter and position capture box

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slide1

ZEBRA

Tom Cobb

slide2

What is a zebra?

  • Zebras (/ˈzɛbrə/ZEB-rə or /ˈziːbrə/ZEE-brə)[1] are several species of African equids (horse family) united by their distinctive black and white stripes.
slide3

What is ZEBRA?

  • A digital signal level converter and position capture box
  • 1U metal box with front panel BNCs and Lemos and rear panel encoder inputs
slide4

What does ZEBRA do?

  • Takes front panel single channel inputs
    • TTL, LVDS, PECL, NIM, Open Collector
  • And rear panel incremental encoder signals
    • A+B RS422 Quadrature decoder, Z, connected
  • Pass the signals through some FPGA logic
    • Logic gates, position capture circuitry
  • Ouput front and rear panel signals
    • Same format as inputs, rewirable at run time
slide6

FPGA Choice

  • Spartan-6 : Low risk, low cost and low power for cost-sensitive applications.
  • Available in TQG144 package.
  • Cost : ~ £10
slide7

FPGA Device Utilisation

  • FPGA is mainly occupied by two modules.
  • Logic Control (41%)
  • Position Capture (37%)
  • SRAM Controller (7%)
  • Picoblaze Comms (3%)
slide8

FPGA Device Utilisation

  • FPGA is almost full...
slide10

How do you configure ZEBRA?

  • 115200 baud RS232 link to EPICS
  • Parameters set/get via EPICS
  • Logic blocks rewired via the system bus
  • Data download of position/time information
  • Save to internal flash
slide12

AND/OR Blocks

INP1

INP2

AND1

slide13

GATE Blocks

INP1

INP2

GATE1

slide14

DIV Blocks

INP1

COUNT

OUTD

slide15

PULSE Blocks

INP1

PULSE1

PULSE2

slide16

QUAD Blocks

STEP

OUTA

OUTB

slide19

What doesn’t ZEBRA do?

  • Analogue
  • Signals < 20ns
  • Low latency data transfer
  • High bandwidth data transfer
  • Sequencing
  • Absolute encoders (yet)
  • For these we would need a ZEBRA2...
slide20

Summary

  • ZEBRA is some level converter circuitry and an FPGA to do logic and position capture
  • EPICS interface over serial line
  • Parts cost about £500 each
  • Looking at making them available for other sites if there is interest