Lab 2: Low and High Pass Filters
================================

This lab lets people explore high and low filters using GNU Radio's blocks programming interface.


.. _x-forwarding:

Setup
-----

| These installation instructions are for people running Windows with OpenSSH already installed (Most modern installations)
| Jumpbox Instructions can be found in the Ara User Manual
|  
|  
| **Install X Display Server On Local Device** - A few examples are below
| vcxsrv - https://sourceforge.net/projects/vcxsrv/ 
| xming - https://sourceforge.net/projects/xming/
|  
| Use default installation settings.
|  
|  
| **Lease Setup**
| - Navigate to https://portal.arawireless.org
| - Reservations > Leases
| - Click "+ create Lease"
| - Lease Name: [anything you want]
| - Leave Start/End Dates blank
| - Click Next
| - Site: Sandbox
| - Device ID: 00X (ex: 001, 002, etc, just can't be the same as someone else's)
| - Click Create Lease
|  
| **Container Setup**
| - Container > Containers
| - Click "+ Create Container"
| - Name: [anything you want]
| - Image: arawirelesshub/uhd:4.4.0.0
| - Leave "Image Driver" and "Image Pull Policy" as defaults
| - Command: bash
| - Click Next
| - Hostname: [anything you want or empty]
| - CPU: 4
| - Memory: 5120
| - Lease name: [select the name of the lease you just created]
| - Click Next
| - Click the arrow on the "ARA_Shared_Net" row, like below:
.. figure:: /images/hw-lab-shared-subnet.png
| - Click "Create"
| - Click on the container name
| - Click the "Console" tab
|  
| **SSH Setup**
| On the console run these commands replacing [username] with your prefered username:
.. code-block:: bash

  apt update

.. code-block:: bash

  apt install openssh-server
.. code-block:: bash
 
  service ssh start

.. code-block:: bash

  useradd -s /usr/bin/bash [username]

.. code-block:: bash

  passwd [username]

.. code-block:: bash

  passwd

.. code-block:: bash

  mkdir /home/[username]

.. code-block:: bash

  chown [username] /home/[username]

| **On local device**
| Open Powershell and run these commands:

.. code-block:: bash

  ssh -J [jbox-username]@jbox.arawireless.org [container-username]@[floating-ip]

.. code-block:: bash

  su

| You should be signed into the container.  On the container run these commands:

.. code-block:: bash

  xauth
| Ctrl + c to exit xauth

.. code-block:: bash

  touch /root/.Xauthority

.. code-block:: bash

  exit

.. code-block:: bash

  xauth
| Ctrl + c to exit xauth

.. code-block:: bash

  touch /home/[username]/.Xauthority

.. code-block:: bash

  su

.. code-block:: bash

  apt install -y gnuradio git cmake g++ libboost-all-dev libgmp-dev swig python3-numpy python3-mako python3-sphinx python3-lxml doxygen libfftw3-dev libsdl1.2-dev libgsl-dev libqwt-qt5-dev libqt5opengl5-dev python3-pyqt5 liblog4cpp5-dev libzmq3-dev python3-yaml python3-click python3-click-plugins python3-zmq python3-scipy python3-gi python3-gi-cairo gir1.2-gtk-3.0 libcodec2-dev libgsm1-dev libusb-1.0-0 libusb-1.0-0-dev libudev-dev python3-pip nano xorg openbox && pip install plotext && pip install matplotlib && pip3 install --user --upgrade manchester-code

.. code-block:: bash

  nano ~/.bashrc
| Add the following lines to the end of the file:

.. code-block:: txt

  export PYTHONPATH="${PYTHONPATH}:/usr/local/local/lib/python3.10/dist-packages/"
  export UHD_IMAGES_DIR=/usr/local/share/uhd/images
  export QT_QPA_PLATFORM_PLUGIN_PATH=/usr/lib/x86_64-linux-gnu/qt5/plugins/platforms
| Ctrl + S and Ctrl + X to save and close

.. code-block:: bash

  source ~/.bashrc

.. code-block:: bash

  uhd_images_downloader

.. code-block:: bash

  nano /etc/ssh/sshd_config
| Uncomment out and change the following line to this:

.. code-block:: txt

  X11UseLocalhost no
| Ctrl + S and Ctrl + X to save and close
.. code-block:: bash

  service ssh restart

.. code-block:: bash

  exit

.. code-block:: bash

  exit

| **Start X Forwarding Session**
| Open XLaunch or Xming on local device (keep clicking next through all menus, leaving everything default) depending on X Server installed above
|  
| Go back to powershell and run these commands:

.. code-block:: bash

  $env:DISPLAY = '127.0.0.1:0'

.. code-block:: bash

  ssh -v -Y -J [jbox-username]@jbox.arawireless.org [container-username]@[floating-ip]

.. code-block:: bash

  xauth list
| Copy returned line to clipboard

.. code-block:: bash

  su

.. code-block:: bash

  xauth add [line copied to clipboard]
| Test X Forwarding

.. code-block:: bash

  xclock

| **Start GNU Radio**

.. code-block:: bash

  gnuradio-companion


Hardware Filter Lab
-------------------

| **Setup Environment**

| You either follow the instructions below or clone the website's GitHub for /python_lab_scripts/high_low_freq_scan.grc a premade GNU Radio Flow Graph.  All blocks can be searched for using Ctrl+f
|  
| GNU Radio should automatically open a new project.
|  
| Double click the options block and set the parameters like below:
.. figure:: /images/hw-lab-options-config.png
| Save and close the window
|  
| Double click the samp_rate variable block and set the parameters like below:
.. figure:: /images/hw-lab-samprate-config.png
| Save and close the window
|  
| Add three more variables for cutoff_freq, tran_width, and gain then set the parameters as follows:
.. figure:: /images/hw-lab-all-variables.png
|  
| Add a USRP Source Block and set the parameters under the RF Options tab as follows:
.. figure:: /images/hw-lab-usrp-source-config.png
|  
| Add a High Pass and a Low Pass Filter Block and set the parameters as follows (Same for both):
.. figure:: /images/hw-lab-highpass-config.png
| 
| Add QT GUI Frequency Sink Block, Null Source, and Null Sink Block.  They don't need to be changed and can be connected as follows:
.. figure:: /images/hw-lab-flowgraph.png
|  
|  
| **The Experiment**
| Press the play button at the top.  Examine the frequency graph that is outputted.
|  
| Experiment with changing the cutoff frequency and transition width variables and restart the graph.
| What changes did you notice with each variable changed?
|  
| Flip the Low Pass Filter block out for the High Pass Filter Block.
| What has changed with the stopband and passband on the graph that's outputted?