GUPPI2 Testing Instructions

This page describes how to run a GBT test observation with GUPPI2 (coherent dedispersion modes of guppi).

Preliminary setup

  • To set up the IF routes, etc, run a standard GUPPI1 astrid configuration block. The only settings that really matter are the receiver, center frequency, bandwidth and cal state.
  • Run a Balance(). This will set input levels correctly for either GUPPI1 or GUPPI2. Levels can be checked using guppi_adc_hist as normal.
  • Important note: After the correct Configure() is done, do not run any more Configure() or Track() statements. Balance() and Slew() are fine.

Loading BOFs

  • Source guppi.csh/bash.
  • Open up a guppi interpreter.
  • At the guppi prompt run mode("c512") to select 512-channel coherent mode. Allowed modes are c64, c128, ..., c2048.
  • Run init() to set up the basic BOF parameters.
  • Run arm() to start data flowing.

Setting levels

  • There are two scale parameters, one for each polarization, BEE2/FPGA2/SCALE_P0 and BEE2/FPGA2/SCALE_P1.
  • To check levels, log in to a gpu node and run -c512 (replace 512 with the appropriate number of channels). To check all at once from beef, run gpu_run -c512.
  • The maximum RMS in any channel should be about 20 counts. Remember to check the highest part of the overall bandpass! This is most important in search mode since the data are re-quantized back to 8 bits after dedispersion/downsampling. Fold mode is much less sensitive.
  • Change the scales using the usual set() syntax at the guppi prompt.
  • For 800-MHz modes with 512 channels at L-band or S-band, the following commands should give good levels (after a balance):
    • set("BEE2/FPGA2/SCALE_P0", "0800000")
    • set("BEE2/FPGA2/SCALE_P1", "0800000")

Setting up an observation

  • Run guppi_set_params to change any observation parameters. Example setups for each common mode:
    • Cal: guppi_set_params -f -U -i -c -b 2048 -t 10.0 -T 60.0
    • Fold: guppi_set_params -f -U -i -m FOLD -b 2048 -t 15.0 -T 3600.0 -P pulsar.par
    • Search: guppi_set_params -f -U -i -m SEARCH -T 3600.0 -P pulsar.par --dstime=16
  • Note that a parfile needs to be given even if you are taking search mode data. In this case, a fake parfile can be made that contains only the DM line.

Taking data

  • Run either guppi2_fold for cal/fold mode, or guppi2_search for search mode.
  • Wait several seconds then run arm() at the guppi prompt to start data recording.
  • While doing this, guppi_status can be run on any of the gpu nodes to make sure data is flowing, etc.
  • On beef, guppi_gpu_status gives an overview of all gpu nodes.
  • The datataking processes log output to the /home/gpu/logs directory.
  • To stop an observation, run guppi2_stop.

Where's my data?

  • All data is written into /data/gpu/partial/(hostname) on each gpu node.

Cleaning up

  • When you are finished observing in coherent mode, run Conform Parameters to restore GUPPI to its original state.

Replacing a GPU node

  • Edit (as monctrl group) /home/gbt/etc/config/Guppi.conf to have the correct hex IP addresses
  • Edit (as guppi group) /opt/64bit/guppi/guppi_daq/gpu_nodes.cfg to have the correct hostnames in order
Topic revision: r5 - 2012-07-30, PaulDemorest

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