Signal Hound VSG25 API for 64-bit Linux systems

Email/Support: support@signalhound.com

-- Description -- 
The API provides a direct I/Q transmit interface for the VSG25 device.
The Linux API shares examples and documentation with the Windows version. 

-- Compilation Notes -- 
The API is compiled on Ubuntu 18.04 using g++ 7.4.0 as a shared object library.

-- Device Permissions --
To run an application interfacing a serial USB device, you need to be have
root permissions. You can either run your application as root or change permissions for the device.

-- Changing Device Permissions --
If you do not want to run your application with root permissions, 
you will need to change permissions for the Signal Hound VSG25 device. 
You will need to copy the sh_usb.rules file in the /etc/udev/rules.d/ directory. 
Once you have done this, you will need to unplug and plug in the device for the rules to take effect. 
You should then be able to interface the device without root permissions.

-- Installation --
The VSG25 API is a 64 bit shared library. The library can be found in the lib/ folder.
The best way to develop to the sg_api is to place the included libraries in the /usr/local/lib directory. 
Steps to perform this are below.

To install the shared library on your system from the lib folder, type

    sudo cp libsg_api.* /usr/local/lib
    sudo ldconfig -v -n /usr/local/lib
    sudo ln -sf /usr/local/lib/libsg_api.so.1 /usr/local/lib/libsg_api.so
 
This should create the necessary symlinks to the main library and place them in the library directory.

The shared library can now be linked in with g++ by
    g++ sources -o output_exe -Wl, -rpath /usr/local/lib -lsg_api
