def AI_start_delay(device_name):
if 'PFI0' not in DAQmxGetDevTerminals(device_name):
return None
task = Task()
clock_terminal = '/' + device_name + '/PFI0'
rate = DAQmxGetDevAIMaxSingleChanRate(device_name)
Vmin, Vmax = DAQmxGetDevAIVoltageRngs(device_name)[0:2]
num_samples = 1000
chan = device_name + '/ai0'
task.CreateAIVoltageChan(chan, "", c.DAQmx_Val_RSE, Vmin, Vmax,
c.DAQmx_Val_Volts, None)
task.CfgSampClkTiming("", rate, c.DAQmx_Val_Rising, c.DAQmx_Val_ContSamps,
num_samples)
task.CfgDigEdgeStartTrig(clock_terminal, c.DAQmx_Val_Rising)
start_trig_delay = float64()
delay_from_sample_clock = float64()
sample_timebase_rate = float64()
task.GetStartTrigDelay(start_trig_delay)
task.GetDelayFromSampClkDelay(delay_from_sample_clock)
task.GetSampClkTimebaseRate(sample_timebase_rate)
task.ClearTask()
total_delay_in_ticks = start_trig_delay.value + delay_from_sample_clock.value
total_delay_in_seconds = total_delay_in_ticks / sample_timebase_rate.value
return total_delay_in_seconds
def AI_start_delay(device_name):
"""Empirically determines the analog inputs' start delay.
Args:
device_name (str): NI-MAX device name
Returns:
float: Analog input start delay in seconds. `None` if
analog inputs not supported.
"""
if 'PFI0' not in DAQmxGetDevTerminals(device_name):
return None
task = Task()
clock_terminal = '/' + device_name + '/PFI0'
rate = DAQmxGetDevAIMaxSingleChanRate(device_name)
Vmin, Vmax = DAQmxGetDevAIVoltageRngs(device_name)[0:2]
num_samples = 1000
chan = device_name + '/ai0'
supp_types = DAQmxGetPhysicalChanAITermCfgs(chan)
if supp_types & c.DAQmx_Val_Bit_TermCfg_RSE:
input_type = c.DAQmx_Val_RSE
elif supp_types & c.DAQmx_Val_Bit_TermCfg_Diff:
input_type = c.DAQmx_Val_Diff
elif supp_types & c.DAQmx_Val_Bit_TermCfg_PseudoDIFF:
input_type = c.DAQmx_Val_PseudoDiff
task.CreateAIVoltageChan(
chan, "", input_type, Vmin, Vmax, c.DAQmx_Val_Volts, None
)
task.CfgSampClkTiming(
"", rate, c.DAQmx_Val_Rising, c.DAQmx_Val_ContSamps, num_samples
)
task.CfgDigEdgeStartTrig(clock_terminal, c.DAQmx_Val_Rising)
start_trig_delay = float64()
delay_from_sample_clock = float64()
sample_timebase_rate = float64()
try:
task.GetStartTrigDelay(start_trig_delay)
except PyDAQmx.DAQmxFunctions.AttributeNotSupportedInTaskContextError:
# device does not have a Start Trigger Delay property
# is likely a dynamic signal acquisition device with filter
# delays instead.
start_trig_delay.value = 0
try:
task.GetDelayFromSampClkDelay(delay_from_sample_clock)
except PyDAQmx.DAQmxFunctions.AttributeNotSupportedInTaskContextError:
# seems simultaneous sampling devices do not have this property,
# so assume it is zero
delay_from_sample_clock.value = 0
task.GetSampClkTimebaseRate(sample_timebase_rate)
task.ClearTask()
total_delay_in_ticks = start_trig_delay.value + delay_from_sample_clock.value
total_delay_in_seconds = total_delay_in_ticks / sample_timebase_rate.value
return total_delay_in_seconds
def AI_filter_delay(device_name):
"""Determine the filter delay for dynamic signal acquistion devices.
Returns the delay in clock cycles. Absolute delay will vary with sample rate.
Args:
device_name (str): NI-MAX device name
Returns:
int: Number of analog input delays ticks between task start and acquisition start.
"""
if 'PFI0' not in DAQmxGetDevTerminals(device_name):
return None
task = Task()
clock_terminal = '/' + device_name + '/PFI0'
rate = DAQmxGetDevAIMaxSingleChanRate(device_name)
Vmin, Vmax = DAQmxGetDevAIVoltageRngs(device_name)[0:2]
num_samples = 1000
chan = device_name + '/ai0'
task.CreateAIVoltageChan(
chan, "", c.DAQmx_Val_PseudoDiff, Vmin, Vmax, c.DAQmx_Val_Volts, None
)
task.CfgSampClkTiming(
"", rate, c.DAQmx_Val_Rising, c.DAQmx_Val_ContSamps, num_samples
)
task.CfgDigEdgeStartTrig(clock_terminal, c.DAQmx_Val_Rising)
start_filter_delay = float64()
sample_timebase_rate = float64()
# get delay in number of clock samples
task.SetAIFilterDelayUnits("", c.DAQmx_Val_SampleClkPeriods)
task.GetAIFilterDelay("", start_filter_delay)
task.GetSampClkTimebaseRate(sample_timebase_rate)
task.ClearTask()
return int(start_filter_delay.value)
