Add Linux support and DAQmx v20.1.0 (#28)

Author: urlicht

Project.toml

@@ -1,6 +1,6 @@
 name = "NIDAQ"
 uuid = "66b72792-1abf-55ab-8064-6e9051317175"
-version = "0.5.0"
+version = "0.6.0"
 
 [compat]
 julia = "0.7, 1"

README.md

@@ -12,25 +12,34 @@ Similar functionality for the Python language is provided by
 
 System Requirements
 ===================
+**General**
+- Supports Windows and Linux
+- NI-DAQmx Base is not supported  
 
-NI-DAQmx Base is not supported, so you'll need a Windows box, and a National
-Instruments card of course.
-
+**Linux specific**  
+- Requires the latest DAQmx (currently 20.1)
+- DAQmx on linux does not support USB DAQ devices
 
 Installation
 ============
-
+**Windows**  
 First download and install NI-DAQmx version
-[19.6](https://www.ni.com/en-us/support/downloads/drivers/download/packaged.ni-daqmx.333268.html) (or
+[20.1](https://www.ni.com/en-us/support/downloads/drivers/download.ni-daqmx.html#348669) (or 
+[19.6](https://www.ni.com/en-us/support/downloads/drivers/download/packaged.ni-daqmx.333268.html), 
 [18.6](http://www.ni.com/en-us/support/downloads/drivers/download/unpackaged.ni-daqmx.291872.html);
 or for Julia 0.6, [17.1.0](http://www.ni.com/download/ni-daqmx-17.1/6836/en/);
 or for Julia 0.5, [16.0.0](http://www.ni.com/download/ni-daqmx-16.0/6120/en/);
 or for Julia 0.4, [15.1.1](http://www.ni.com/download/ni-daqmx-15.1.1/5665/en/);
 or for Julia 0.3, [14.1.0](http://www.ni.com/download/ni-daqmx-14.1/4953/en/),
 [14.0.0](http://www.ni.com/download/ni-daqmx-14.0/4918/en/), or
 [9.6.0](http://www.ni.com/download/ni-daqmx-9.6/3423/en/)) from National
-Instruments.  Then on the Julia command line:
+Instruments.
+
+**Linux**  
+The package only supports DAQmx 20.1 on linux. Follow the instructions from this [support doc](https://www.ni.com/en-us/support/documentation/supplemental/18/downloading-and-installing-ni-driver-software-on-linux-desktop.html).
 
+**Adding `NIDAQ.jl`**  
+Then on the Julia command line:
 ```
 ]add NIDAQ
 ```

src/NIDAQ.jl

@@ -44,7 +44,8 @@ export counter_input_channels, counter_output_channels
 
 export RSE, NRSE, Differential, PseudoDifferential
 
-const NIDAQmx = "C:\\Windows\\System32\\nicaiu.dll"
+const NIDAQmx = Sys.iswindows() ? "C:\\Windows\\System32\\nicaiu.dll" :
+    "/usr/lib/x86_64-linux-gnu/libnidaqmx.so"
 const SafeCstring = Ref{UInt8}
 
 primitive type Bool32<:Integer 32 end