National Instruments Data Acquisition Interface


National Instruments Data Acquisition Interface

This package provides an interface to NI-DAQmx--- National Instruments' driver for their data acquisition boards. Their entire C header file was ported using Clang.jl, and a rudimentary higher-level API is provided for ease of use.

Similar functionality for the Python language is provided by PyDAQmx.

System Requirements

NI-DAQmx Base is not supported, so you'll need a Windows box, and a National Instruments card of course.


First download and install NI-DAQmx version 19.6 (or 18.6; or for Julia 0.6, 17.1.0; or for Julia 0.5, 16.0.0; or for Julia 0.4, 15.1.1; or for Julia 0.3, 14.1.0, 14.0.0, or 9.6.0) from National Instruments. Then on the Julia command line:

]add NIDAQ

Basic Usage

With no input arguments, the high-level getproperties function can be used to query the system:

julia> using NIDAQ

julia> getproperties()
Dict{String,Tuple{Any,Bool}} with 7 entries:
  "DevNames"           => (SubString{String}["Dev1"],false)
  "GlobalChans"        => (SubString{String}[""],false)
  "NIDAQMajorVersion"  => (0x00000010,false)
  "NIDAQMinorVersion"  => (0x00000000,false)
  "NIDAQUpdateVersion" => (0x00000000,false)
  "Scales"             => (SubString{String}[""],false)
  "Tasks"              => (SubString{String}[""],false)

Returned is a dictionary of tuples, the first member indicating the property value and the second a boolean indicating whether the former is mutable.

getproperties can also input a string containing the name of a data acquisition device:

julia> getproperties("Dev1")
Dict{String,Tuple{Any,Bool}} with 61 entries:
  "AIBridgeRngs"                           => (Float64[],false)
  "AICouplings"                            => (:Val_Transferred_From_Buffer,false)
  "AICurrentIntExcitDiscreteVals"          => (Float64[],false)
  "AICurrentRngs"                          => (Float64[],false)
  "AIDigFltrLowpassCutoffFreqDiscreteVals" => (Float64[],false)
  "AIDigFltrLowpassCutoffFreqRangeVals"    => (Float64[],false)
  "AIFreqRngs"                             => (Float64[],false)
  "AIGains"                                => (Float64[],false)
  "AILowpassCutoffFreqDiscreteVals"        => (Float64[],false)
  "AILowpassCutoffFreqRangeVals"           => (Float64[],false)
  "AIMaxMultiChanRate"                     => (2.0e6,false)
  "AIMaxSingleChanRate"                    => (2.0e6,false)
  "AIMinRate"                              => (0.0232831,false)
  "AIPhysicalChans"                        => (SubString{String}["Dev1/ai0","Dev1/ai1","Dev1/ai2",".
  "AIResistanceRngs"                       => (Float64[],false)
  "AISampModes"                            => (Symbol[:Val_FiniteSamps,:Val_ContSamps],false)
  "AISupportedMeasTypes"                   => (Symbol[:Val_Current,:Val_Resistance,:Val_Strain_Gage.
  "AITrigUsage"                            => (14,false)
  "AIVoltageIntExcitDiscreteVals"          => (Float64[],false)
  "AIVoltageIntExcitRangeVals"             => (Float64[],false)
  "AIVoltageRngs"                          => ([-1.0,1.0,-2.0,2.0,-5.0,5.0,-10.0,10.0],false)
  "AOCurrentRngs"                          => (Float64[],false)
  "AOGains"                                => (Float64[],false)
  "AOMaxRate"                              => (3.33333e6,false)
  "AOMinRate"                              => (0.0232831,false)
  "AOPhysicalChans"                        => (SubString{String}["Dev1/ao0","Dev1/ao1"],false)
  "AOSampModes"                            => (Symbol[:Val_FiniteSamps,:Val_ContSamps],false)
  "AOSupportedOutputTypes"                 => (Symbol[:Val_Voltage],false)
  "AOTrigUsage"                            => (10,false)
  "AOVoltageRngs"                          => ([-5.0,5.0,-10.0,10.0],false)
  "AccessoryProductNums"                   => (UInt32[0x00000000],false)
  "AccessoryProductTypes"                  => (SubString{String}[""],false)
  "AccessorySerialNums"                    => (UInt32[0x00000000],false)
  "BusType"                                => (:Val_USB,false)
  "CIMaxSize"                              => (0x00000020,false)
  "CIMaxTimebase"                          => (1.0e8,false)
  "CIPhysicalChans"                        => (SubString{String}["Dev1/ctr0","Dev1/ctr1","Dev1/ctr2.
  "CISampModes"                            => (Symbol[:Val_FiniteSamps,:Val_ContSamps],false)
  "CISupportedMeasTypes"                   => (Symbol[:Val_CountEdges,:Val_Freq,:Val_Period,:Val_Tw.
  "CITrigUsage"                            => (42,false)
  "COMaxSize"                              => (0x00000020,false)
  "COMaxTimebase"                          => (1.0e8,false)
  "COPhysicalChans"                        => (SubString{String}["Dev1/ctr0","Dev1/ctr1","Dev1/ctr2.
  "COSampModes"                            => (Symbol[:Val_FiniteSamps,:Val_ContSamps],false)
  "COSupportedOutputTypes"                 => (Symbol[:Val_Pulse_Freq,:Val_Pulse_Ticks,:Val_Pulse_T.
  "COTrigUsage"                            => (42,false)
  "ChassisModuleDevNames"                  => (SubString{String}[""],false)
  "DILines"                                => (SubString{String}["Dev1/port0/line0","Dev1/port0/lin.
  "DIMaxRate"                              => (1.0e7,false)
  "DIPorts"                                => (SubString{String}["Dev1/port0","Dev1/port1","Dev1/po.
  "DITrigUsage"                            => (14,false)
  "DOLines"                                => (SubString{String}["Dev1/port0/line0","Dev1/port0/lin.
  "DOMaxRate"                              => (1.0e7,false)
  "DOPorts"                                => (SubString{String}["Dev1/port0","Dev1/port1","Dev1/po.
  "DOTrigUsage"                            => (10,false)
  "NumDMAChans"                            => (0x00000000,false)
  "ProductCategory"                        => (:Val_XSeriesDAQ,false)
  "ProductNum"                             => (0x000075a1,false)
  "ProductType"                            => (SubString{String}["USB-6366 (64 MS) (Mass Terminatio.
  "SerialNum"                              => (0x01719e54,false)
  "Terminals"                              => (SubString{String}["/Dev1/PFI0","/Dev1/PFI1","/Dev1/P.

One can index into the dictionary to get a list of channels:

julia> getproperties("Dev1")["AIPhysicalChans"]

A bit simpler in this case though is to use another high-level function which returns just the string Array:

julia> analog_input_channels("Dev1")
8-element Array{String,1}:

To add, for example, analog input channels, use the high-level analog_input function:

julia> t = analog_input("Dev1/ai0:1")
NIDAQ.AITask(Ptr{Nothing} @0x0000000025d18600)

julia> typeof(t)
NIDAQ.AITask (constructor with 3 methods)

julia> supertype(NIDAQ.AITask)

Two channels were added above using the : notation. Additional channels can be added later by inputing the returned Task:

julia> analog_input(t, "Dev1/ai2")

getproperties can also input a Task:

julia> getproperties(t)
Dict{String,Tuple{Any,Bool}} with 5 entries:
  "Devices"    => (SubString{String}["Dev1"],false)
  "Channels"   => (SubString{String}["Dev1/ai0","Dev1/ai1","Dev1/ai2"],false)
  "Name"       => (SubString{String}["_unnamedTask<0>"],false)
  "NumChans"   => (0x00000003,false)
  "NumDevices" => (0x00000001,false)

as well as a string containing the name of the channel:

julia> getproperties(t, "Dev1/ai0")
Dict{String,Tuple{Any,Bool}} with 52 entries:
  "AccelUnits"                        => (:Val_g,false)
  "AutoZeroMode"                      => (:Val_None,false)
  "BridgeUnits"                       => (:Val_VoltsPerVolt,false)
  "ChanCalDesc"                       => (SubString{String}[""],false)
  "ChanCalOperatorName"               => (SubString{String}[""],false)
  "ChanCalPolyForwardCoeff"           => (Float64[],false)
  "ChanCalPolyReverseCoeff"           => (Float64[],false)
  "ChanCalScaleType"                  => (:Val_Table,false)
  "ChanCalTablePreScaledVals"         => (Float64[],false)
  "ChanCalTableScaledVals"            => (Float64[],false)
  "ChanCalVerifAcqVals"               => (Float64[],false)
  "ChanCalVerifRefVals"               => (Float64[],false)
  "Coupling"                          => (:Val_DC,false)
  "CurrentACRMSUnits"                 => (:Val_Amps,false)
  "CurrentUnits"                      => (:Val_Amps,false)
  "CustomScaleName"                   => (SubString{String}[""],false)
  "DataXferMech"                      => (:Val_ProgrammedIO,false)
  "DataXferReqCond"                   => (:Val_OnBrdMemNotEmpty,false)
  "DevScalingCoeff"                   => ([0.000102924,0.000312673,5.87393e-14,-3.31855e-19],false)
  "EddyCurrentProxProbeUnits"         => (:Val_Meters,false)
  "ForceUnits"                        => (:Val_Newtons,false)
  "FreqUnits"                         => (:Val_Hz,false)
  "Gain"                              => (1.0,false)
  "InputSrc"                          => (SubString{String}["_external_channel"],false)
  "LVDTUnits"                         => (:Val_Meters,false)
  "LossyLSBRemovalCompressedSampSize" => (0x00000010,false)
  "Max"                               => (10.0,false)
  "MeasType"                          => (:Val_Voltage,false)
  "Min"                               => (-10.0,false)
  "PressureUnits"                     => (:Val_PoundsPerSquareInch,false)
  "RVDTUnits"                         => (:Val_Degrees,false)
  "RawDataCompressionType"            => (:Val_None,false)
  "RawSampJustification"              => (:Val_RightJustified,false)
  "RawSampSize"                       => (0x00000010,false)
  "ResistanceUnits"                   => (:Val_Ohms,false)
  "Resolution"                        => (16.0,false)
  "ResolutionUnits"                   => (:Val_Bits,false)
  "RngHigh"                           => (10.0,false)
  "RngLow"                            => (-10.0,false)
  "SoundPressureUnits"                => (:Val_Pascals,false)
  "StrainGageCfg"                     => (:Val_FullBridgeI,false)
  "StrainUnits"                       => (:Val_Strain,false)
  "TempUnits"                         => (:Val_DegC,false)
  "TermCfg"                           => (:Val_Diff,false)
  "ThrmcplCJCVal"                     => (25.0,false)
  "TorqueUnits"                       => (:Val_NewtonMeters,false)
  "UsbXferReqCount"                   => (0x00000004,false)
  "UsbXferReqSize"                    => (0x00008000,false)
  "VelocityUnits"                     => (:Val_MetersPerSecond,false)
  "VoltageACRMSUnits"                 => (:Val_Volts,false)
  "VoltageUnits"                      => (:Val_Volts,false)
  "VoltagedBRef"                      => (1.0,false)

Use setproperty! to change a mutable property:

julia> setproperty!(t, "Dev1/ai0", "Max", 5.0)

Once everything is configured, get some data using the read function:

julia> start(t)

julia> read(t, 10)
10x3 Array{Float64,2}:
 1.52407   -0.448835   0.381075
 1.37546   -0.213537   0.305847
 1.2363    -0.0268698  0.262826
 1.109      0.118619   0.243117
 0.995797   0.2311     0.240073
 0.896695   0.315782   0.248004
 0.811452   0.378752   0.262746
 0.739429   0.424257   0.281893
 0.679263   0.456223   0.302402
 0.629672   0.477774   0.323473

julia> stop(t)

julia> clear(t)

read can also return Int16, Int32, UInt16, and UInt32 by specifying those types as an additional argument:

julia> read(t, 10, Int16)
10×3 Array{Int16,2}:
 -12619  -5351  -13973
 -12618  -5350  -13973
 -12620  -5350  -13973
 -12619  -5350  -13974
 -12618  -5351  -13972
 -12618  -5348  -13974
 -12619  -5350  -13973
 -12619  -5350  -13973
 -12619  -5350  -13972
 -12620  -5350  -13973

Similar work flows exist for analog_output, digital_input, and digital_output. The high-level API also supports many counter functions too, including count_edges and generate_pulses. For a full list of convenience functions use the names function in Julia Base:

julia> names(NIDAQ)
25-element Array{Symbol,1}:

NIDAQmx is a powerful interface, and while NIDAQ.jl provides wrappers for all of it's functions, it only abstracts a few of them. If these don't suit your needs you'll have to dive deep into src/functions_V*.jl and src/constants_V*.jl. Complete documentation of this low-level API is here and here.

One situation where the low-level API is needed is to specify continous output of pulses using a counter:

julia> t = generate_pulses("Dev1/ctr0")
NIDAQ.COTask(Ptr{Nothing} @0x00000000059d8790)

julia> fieldnames(typeof(t))

julia> NIDAQ.CfgImplicitTiming(t.th, NIDAQ.Val_ContSamps, UInt64(1))

Note that tasks consist of just a single field th, and that this "task handle" is what must be passed into many low-level routines.

Also, for brevity NIDAQ.jl strips the "DAQmx" prefix to all functions and constants in NI-DAQmx, and converts the latter to 32 bits. One must still take care to caste the other inputs appropriately though.

Adding Support for a Version of NI-DAQmx

Install Clang.jl. If there are build problems, make sure that llvm-config is on your PATH, and that libclang can be found, as described in the Clang.jl README. Clang defaults to using a system installed version of LLVM. An alternative is to set BUILD_LLVM_CLANG=1 in Make.user, and compile Julia from source.

Find NIDAQmx.h, which usually lives in C:\Program Files (x86)\National Instruments\NI-DAQ\DAQmx ANSI C Dev\include.

Edit this header file as follows:

  • For NI-DAQmx v19.6 in NIDAQmx.h change __int64 int64 to long long int int64 and unsigned __int64 uInt64 to unsigned long long uInt64.
  • For NI-DAQmx v9.6.0 in NIDAQmx.h change defined(__linux__) to defined(__linux__) || defined(__APPLE__).

Then run Clang to produce the corresponding Julia files:

julia> using Clang
julia> wc = init(; headers = ["NIDAQmx.h"],
                   output_file = "NIDAQmx.jl",
                   common_file = "common.jl",
                   clang_includes = vcat(CLANG_INCLUDE),
                   clang_args = map(x->"-I"*x, find_std_headers()),
                   header_wrapped = (root, current)->root == current,
                   header_library = x->"NIDAQmx",
                   clang_diagnostics = true)
julia> run(wc)
$ mv NIDAQmx.jl src/functions_V<version>.jl
$ mv common.jl src/constants_V<version>.jl
$ rm LibTemplate.jl ctypes.jl

Finally, the following manual edits are necessary:

  • In constants_V<version>.jl
    • delete const CVICALLBACK = CVICDECL,
    • in NI-DAQmx v19.6 add struct CVITime; lsb::uInt64; msb::int64; end
    • in NI-DAQmx v17.1.0 comment out const CVIAbsoluteTime = VOID
    • change const bool32 = uInt32 to const bool32 = Bool32.
    • in NI-DAQmx v15 to v18 comment out using Compat
  • In functions_V<version>.jl
    • in NI-DAQmx v18 and earlier, globally search for Ptr and replace with Ref, then globally search for CallbackRef and replace with CallbackPtr.
    • globally search for Cstring and replace with SafeCstring
    • for Julia 0.7 support, replace type with _type


Ben Arthur, arthurb@hhmi.org
Scientific Computing
Janelia Research Campus
Howard Hughes Medical Institute


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