def fetch(filename, nevents, runattrs=None):
"""
Fetch and save waveform traces from the oscilloscope.
Args:
- filename: str
Filename to store traces in (in hdf5 format).
- nevents: int
Number of triggered events to save in `filename`.
"""
scope = LeCroyScope(setup.scope_ip, timeout=20.0)
# turn off the display
scope.send('display off')
scope.check_last_command()
# clear the output queue
scope.clear()
# get active channels
channels = scope.getchannels()
# get scope configuration
settings = get_settings(scope)
# get wave descriptors for each channel
# important to do this before queue is primed!
# need to trigger in order to get correct wave_array_count
scope.trigger()
time.sleep(5.0)
wavedesc = {}
for channel in channels:
wavedesc[channel] = scope.getwavedesc(channel)
# open up the output file
f = h5py.File(filename, 'w')
# set scope configuration
for command, setting in settings.items():
f.attrs[command] = setting
if 'ON' in f.attrs['SEQUENCE']:
sequence_count = int(f.attrs['SEQUENCE'].split(',')[1])
if sequence_count < 1:
raise Exception('sequence count must be a positive number.')
else:
sequence_count = 1
for channel in channels:
nsamples = wavedesc[channel]['wave_array_count'] // sequence_count
f.create_dataset('channel%i' % channel, (nevents, nsamples),
dtype=wavedesc[channel]['dtype'],
chunks=(max(1, min(100, nevents // 100)), nsamples),
compression='gzip')
for key, value in wavedesc[channel].items():
try:
f['channel%i' % channel].attrs[key] = value
except ValueError:
pass
if runattrs is not None:
for name in runattrs:
for key, value in runattrs[name].items():
f[name].attrs[key] = value
# start a timer
time0 = time.time()
try:
i = 0
while True:
print '\rsaving event: %i' % i,
sys.stdout.flush()
try:
scope.trigger()
for channel in channels:
wave_array = scope.getwaveform(channel, wavedesc[channel])
if sequence_count > 1:
try:
f['channel%i' % channel][i:i+sequence_count] = \
wave_array.reshape(sequence_count, wave_array.size//sequence_count)
except ValueError:
f['channel%i' % channel][i:i+sequence_count] = \
wave_array.reshape(sequence_count, wave_array.size//sequence_count)[:len(f['channel%i' % channel])-i]
else:
f['channel%i' % channel][i] = wave_array
except (socket.error, struct.error) as e:
print '\n' + str(e)
scope.clear()
continue
i += sequence_count
if i >= nevents:
print '\rsaving event: %i' % i,
break
print
except KeyboardInterrupt:
print '\nresizing datasets...'
for channel in channels:
f['channel%i' % channel].resize(
(i, wavedesc[channel]['wave_array_count'] // sequence_count))
raise
finally:
f.close()
scope.clear()
scope.send('display on')
scope.check_last_command()
elapsed = time.time() - time0
if i > 0:
print 'Completed %i events in %.3f seconds.' % (i, elapsed)
print 'Averaged %.5f seconds per acquisition.' % (elapsed / i)
print "Wrote to file '%s'." % filename
