def incomplete_sample_detection(device_name):
"""Introspect whether a device has 'incomplete sample detection', described here:
www.ni.com/documentation/en/ni-daqmx/latest/devconsid/incompletesampledetection/
The result is determined empirically by outputting a pulse on one counter and
measuring it on another, and seeing whether the first sample was discarded or not.
This requires a non-simulated device with at least two counters. No external signal
is actually generated by the device whilst this test is performed. Credit for this
method goes to Kevin Price, who provided it here:
forums.ni.com/t5/Multifunction-DAQ/_/td-p/3849429
This workaround will hopefully be deprecated if and when NI provides functionality
to either inspect this feature's presence directly, or to disable it regardless of
its presence.
"""
if is_simulated(device_name):
msg = "Can only detect incomplete sample detection on non-simulated devices"
raise ValueError(msg)
if not supports_period_measurement(device_name):
msg = "Device doesn't support period measurement"
raise ValueError(msg)
CI_chans = get_CI_chans(device_name)
if len(CI_chans) < 2:
msg = "Need at least two counters to detect incomplete sample detection"
raise ValueError(msg)
# The counter we will produce a test signal on:
out_chan = CI_chans[0]
# The counter we will measure it on:
meas_chan = CI_chans[1]
# Set up the output task:
out_task = daqmx.Task()
out_task.CreateCOPulseChanTime(out_chan, "", c.DAQmx_Val_Seconds,
c.DAQmx_Val_Low, 0, 1e-3, 1e-3)
# Prevent the signal being output on the physical terminal:
out_task.SetCOPulseTerm("", "")
# Force CO into idle state to prevent spurious edges when the task is started:
out_task.TaskControl(c.DAQmx_Val_Task_Commit)
# Set up the measurement task
meas_task = daqmx.Task()
meas_task.CreateCIPeriodChan(
meas_chan,
"",
1e-3,
1.0,
c.DAQmx_Val_Seconds,
c.DAQmx_Val_Rising,
c.DAQmx_Val_LowFreq1Ctr,
10.0,
0,
"",
)
meas_task.CfgImplicitTiming(c.DAQmx_Val_ContSamps, 1)
# Specify that we are measuring the internal output of the other counter:
meas_task.SetCIPeriodTerm("", '/' + out_chan + 'InternalOutput')
try:
meas_task.StartTask()
out_task.StartTask()
out_task.WaitUntilTaskDone(10.0)
# How many samples are in the read buffer of the measurement task?
samps_avail = types.uInt32()
meas_task.GetReadAvailSampPerChan(samps_avail)
if samps_avail.value == 0:
# The device discarded the first edge
return True
elif samps_avail.value == 1:
# The device did not discard the first edge
return False
else:
# Unexpected result
msg = "Unexpected number of samples: %d" % samps_avail.value
raise ValueError(msg)
finally:
out_task.ClearTask()
meas_task.ClearTask()
def get_product_type(device_name):
BUFSIZE = 4096
result = ctypes.create_string_buffer(BUFSIZE)
daqmx.DAQmxGetDevProductType(device_name, result, types.uInt32(BUFSIZE))
return result.value.decode('utf8')
def get_CI_chans(device_name):
BUFSIZE = 4096
result = ctypes.create_string_buffer(BUFSIZE)
daqmx.DAQmxGetDevCIPhysicalChans(device_name, result,
types.uInt32(BUFSIZE))
return result.value.decode('utf8').split(', ')
def get_devices():
BUFSIZE = 4096
result = ctypes.create_string_buffer(BUFSIZE)
daqmx.DAQmxGetSysDevNames(result, types.uInt32(BUFSIZE))
return result.value.decode('utf8').split(',')
