I wanted to combine National Instruments data acquisition hardware with Node.js. This is not a 1-to-1 wrapper of the DAQmx C API. I have re-interpreted some of the structures to make using DAQmx a little easier, but tried to be faithful to the original concepts.
If you need the full API, considering using node-ffi to load nicaiu.dll (from the daqmx driver installation) to access all the C API functions.
- Everything needed to build Node.js add-ons (node-gyp and build tools for windows)
- Latest National Instruments DAQmx drivers.
- Either a physical NI device, or a virtual device created using their Measurement and Automation Explorer.
The following examples assume the add-on is loaded into the variable 'daqmx'.
node-gyp rebuild # in root directory of repo
node-gyp installOr just run npm install
This is a fork of kcdodd's repository to bring it upto date and provide 64bit support. By default it is for 64bit, to use it with a 32bit system, change line 7 in 'binding.gpy' to:
"libraries": [ "C:\Program Files (x86)\National Instruments\Shared\ExternalCompilerSupport\C\lib32\msvc\NIDAQmx.lib" ]
To get a list of currently available devices.
var devs = daqmx.devices();
console.log(devs);Returns an array of objects of each device with properties: E.G.
[{
name: "Dev1",
productType: "USB-6000"
},
{
name: "Dev2",
productType: "PCI-6071E"
}]The minimal configuration to acquire a sample must have defined the channels to acquire on, and the timing of the samples. Specifying the channels separately as an array will cause the read to return a 2D array, where the first index is the channels (in the same order), and second index is sample #. There can typically be only one task of each type running per physical device because of how the signals are digitized. There's usually only 1 ADC (or DAC), which is split between the channels.
// read 10 samples from 2 channels at 10,000Hz sample rate
var task = new daqmx.AIVoltageTask({
device: "Dev1",
channels: [{terminal: "ai0"},{terminal: "ai3"}],
sampleTiming: {
rate: 10000.0,
samplesPerChannel: 10
}
});
task.start();
var x = task.read(); // infinite timeout
//var x = task.read(10.0); // 10 second timeout
console.log(x);Alternately, if the terminals are consecutive, they can be specified in a single input. E.G. the following will acquire from 4 terminals (ai0, ai1, ai2, ai3).
var task = new daqmx.AIVoltageTask({
device: "Dev1",
channels: [{terminal: "ai0:3"}],
sampleTiming: {
rate: 10000.0,
samplesPerChannel: 10
}
});The reading of samples can also be done in the Node.js io loop so that it doesn't block the program execution.
// do a read asynchronously
var readAsync = function(callback) {
process.nextTick(function(){
// call canRead() tests if all samples can be read
if (task.canRead()) {
var data = task.read(0.0); // should read immediately
callback(data);
}else{
// not ready so wait until next tick
readAsync(callback);
}
});
};
readAsync(function(data){
console.log(data);
});The AIVoltageTask can be configured with most of the abilities available. These examples are translated from the examples supplied in the DAQmx documentation.
To do continuous sampling of a single channel using the internal clock and a digital start trigger:
var task = new daqmx.AIVoltageTask({
name: "myAIVoltageTask", // optional name for task, default ""
device: "Dev1", // physical device name
channels: [{ // array of objects specifying the channels to acquire
terminal: "ai0", // physical terminal name
assignName: "someChannelName" // optional name for channel
minVal: -10.0, // optional, default -10.0
maxVal: 10.0 // optional, default 10.0
}],
sampleTiming: { // timing for individual samples
terminal: "OnboardClock", // optional, default is 'OnboardClock'
rate: 10000.0, // sample rate in Hz
triggerSlope: "falling", // optional, default rising
sampleMode: "continuous", // optional, default finite
samplesPerChannel: 10 // max number of samples to read per round
},
startTiming: { // optional timing for when to start the task
type: "digital", // analogue, or digital
terminal: "PFI0",
triggerSlope: "falling" // optional, default rising
}
});To do a finite sample of a single channel using an external clock, and an external analogue start trigger including hysteresis.
var task = new daqmx.AIVoltageTask({
name: "myAIVoltageTask",
device: "Dev1",
channels: [{
terminal: "ai0",
minVal: -10.0,
maxVal: 10.0
}],
sampleTiming: {
terminal: "PFI7",
rate: 10000.0,
triggerSlope: "rising",
sampleMode: "finite",
samplesPerChannel: 10
},
startTiming: {
type: "analog",
terminal: "APFI0",
triggerSlope: "rising", // optional, default rising
triggerLevel: 1.0, // analogue trigger only in volts
hysteresis: 1.0 // optional for analogue trigger only, default 0.0
}
});