User Guide

Cover topics:

  • Startup.
  • Acquire.
  • Parameters.
  • Scan.
  • Process.
  • View.
  • Using with DAWN

Getting started: simple scan

A scan of a DAC parameter is a relatively simple task. The following demonstrate how to achieve this with a single loop. The basic steps include:

  • Instansiate a percivalui.percival.PercivalUI object.
  • Configure the percivalui.percival.PercivalUI.data instance to capture data into a file.
  • Scan through a list of DAC values, and for each value command an acquisition of N frames.
  • Wait for file saving to complete.
  • Request the details of where the dataset was stored.
  • Open dataset and start processing.
'''
A simple PercivalUI scan demo

This demonstrates how to do a synchronous scan of a DAC 
parameter while acquiring samples off the detector.
'''

try:
    from pkg_resources import require
    require('h5py')
    require('numpy')
    require('future')
except:
    pass # not everyone use setuptools and that is OK...

import logging
logging.basicConfig()
logger = logging.getLogger()
logger.setLevel(logging.DEBUG)

from percival.percivalui import PercivalUI
import datetime

pcvl = PercivalUI()

# Do a rough scan (steps of 8) through a 12 bit DAC subrange
DAC_scan_values = range(128, 512, 8)

nframes_per_step = 10
nframes_total = nframes_per_step * len(DAC_scan_values)

# Prepare to record the acquired data into a file with a timestamp in the name
start_time = datetime.datetime.now() 
data_filename = 'simplescan_demo_%s.h5'%start_time.isoformat()
pcvl.data.start_capture(data_filename, nframes=nframes_total)

# Scan through the desired DAC values
for DAC_value in DAC_scan_values:
    logger.debug( "Setting DAC \'some_gain\' = %d"%DAC_value )
    # Set the desired control DAC parameter. In this example "some_gain"
    pcvl.control.dacs.some_gain = DAC_value
    
    # Acquire 10 frames for each step with a 0.1s exposure per frame
    # With wait=True, this function will block until aquisition completes
    logger.debug( "Acquiring %d frames" % nframes_per_step )
    pcvl.acquire(0.01, nframes_per_step, wait=True)
    
# Now wait for the data to be stored to disk. This function
# blocks until data capture is complete or stopped.
pcvl.data.wait_complete(timeout = None)

logger.info( "Opening file: %s, dataset: %s" % (pcvl.data.filename,  pcvl.data.datasetname) )
# Access the real data through h5py
import h5py
h5file = h5py.File(pcvl.data.filename, 'r')
dset = h5file[pcvl.data.datasetname]

logger.info( "Acquire dataset dimensions: %s", str(dset.shape) )

PercivalUI in DAWN

  • Configuring dawn to pick up the python packages.
  • Acquire data
  • Plot results
  • Example scan