Getting Started with RFNoC Development

Overview

This application note gives a brief introduction into the steps required to start developing RFNoC blocks on your computer. First, you need to make sure that you have all the tools required to do RFNoC development. Then, we will set up a development sandbox in which you can do your RFNoC development. Finally, we will run through the basic steps required to actually write custom RFNoC blocks.

Prerequisites

For any of this to work, you need to make sure you have all the tools to do both software and FPGA development. Confirm you have the following tools installed:

• Xilinx Vivado. The specific version depends on the branch and state of the FPGA code and is very important. Make sure to install the correct version.
• Software build tools. If you can compile UHD from source, you have all the necessary components (If you're using PyBOMBS

Please make sure these tools are available before proceeding to the next step.

Creating a development environment

In the following, we will assume that GNU Radio is used as a helper tool for RFNoC development. Note that GNU Radio is by no means required to use or develop RFNoC, but it makes it a great deal easier. So in order to get your development environment set up, you will need the following software packages:

- UHD - GNU Radio - gr-ettus

The cleanest way to set this up is to install everything into a dedicated directory. PyBOMBS is the simplest way to do this. If you haven't already downloaded and installed PyBOMBS, you can do so by running the following commands:

   $ sudo pip install git+https://github.com/gnuradio/pybombs.git
   $ pybombs recipes add gr-recipes git+https://github.com/gnuradio/gr-recipes.git
   $ pybombs recipes add ettus git+https://github.com/EttusResearch/ettus-pybombs.git

From here, the easiest way to set up a PyBOMBS development environment is to run the following command:

   $ pybombs prefix init ~/prefix/rfnoc -R rfnoc [-a alias]

This will do the following:

- Create a directory in ~/prefix/rfnoc - Clone UHD, FPGA, GNU Radio, and gr-ettus sources into that directory - Compile and install all the software

Then, enable the prefix:

   $ cd ~/prefix/rfnoc
   $ source ./setup_env.sh

PyBOMBS is by no means required to do any of these steps. If you wish to install the software manually, follow the individual install notes for GNU Radio, UHD and gr-ettus and make sure they are reachable by linkers and compilers.

To manually download the software, use these git clone commands, which will select the correct branches:

   $ git clone --recursive -b rfnoc-radio-redo https://github.com/EttusResearch/uhd.git
   $ git clone -b maint https://github.com/gnuradio/gnuradio.git # master branch is also fine
   $ git clone -b radio-redo https://github.com/EttusResearch/gr-ettus.git

If you have already UHD, GNU Radio and/or gr-ettus installed, it would be sufficient to checkout to the branches mentioned and pull them. Thereafter, build each of the repositories (first UHD, then GNU Radio, then gr-ettus).

rfnocmodtool

In order to minimize the effort needed to implement a new RFNoC module, this gr_modtool-based tool provides the basic structure of the necessary files needed for the user to start with the development of his/her custom design right away. As it is gr_modtool-based, the manual found at [1] is also a great reference for this tool. Here, we discuss the features specific for the RFNoC modtool.

With the use of RFNoC ModTool, you can skip the struggle of locating the files of your design at different locations that depend (until now) on the location of your UHD and gr-ettus installation paths. Instead, you focus on your implementation and the tool takes care of boilerplate code and linking.

Tool Installation

The tool is currently shipped within gr-ettus (radio-redo branch), so by installing gr-ettus, rfnocmodtool automatically becomes available.

Tool Utilization

After the installation, you are ready to use the tool to generate standard code for your Out-of-tree module. To check the usage of the tool, just type:

   $ rfnocmodtool help

   linux; GNU C++ version 4.8.4; Boost_105400; UHD_003.010.rfnoc-radio-redo-0-fd4d734e
   Usage:
   rfnocmodtool <command> [options] -- Run <command> with the given options.
   rfnocmodtool help -- Show a list of commands.
   rfnocmodtool help <command> -- Shows the help for a given command. 

   List of possible commands:

   Name      Aliases          Description
   =====================================================================
   disable   dis              Disable block (comments out CMake entries for files) 
   info      getinfo,inf      Return information about a given module 
   remove    rm,del           Remove block (delete files and remove Makefile entries) 
   makexml   mx               Make XML file for GRC block bindings 
   add       insert           Add block to the out-of-tree module. 
   newmod    nm,create        Create a new out-of-tree module 
   rename    mv               Rename a block in the out-of-tree module. 

If you have used the gr_modtool provided by GNURadio, you'll be familiar with this usage.

Creating an RFNoC OOT Module

At this point you are all set up to start generating your own RFNoC OOT and if you were thinking that it is just as easy as it is with gr_modtool, you are completely right! Simply go to your prefixes source location (~/prefix/rfnoc/src) and type:

   $ rfnocmodtool newmod [NAME OF THE MODULE]

In the following, assume we want to create a module with the name 'example'. You can write the name of your module right after the 'newmod' command, but if you happen to forget it, the tool will ask for it interactively. This will create a folder containing the basic folders that you may need for a functional module.

   $ rfnocmodtool newmod example
   linux; GNU C++ version 4.8.4; Boost_105400; UHD_003.010.rfnoc-radio-redo-0-fd4d734e

   Creating out-of-tree module in ./rfnoc-example... Done.
   Use 'rfnocmodtool add' to add a new block to this currently empty module.

   $ ls rfnoc-example/
   $ apps  cmake  CMakeLists.txt  docs  examples  grc  include  lib  MANIFEST.md  python  README.md  rfnoc  swig

In contrast with gr_modtool, this includes a folder called 'rfnoc', which is where we put the UHD/FPGA files (more details below).

Adding custom blocks

Now you can start adding blocks to your module. The only thing to do is go inside of the module you just created and type:

   $ rfnocmodule add [NAME OF THE BLOCK]

Other Resources

[1] GNURadio OutOfTree Modules: http://gnuradio.org/redmine/projects/gnuradio/wiki/OutOfTreeModules

https://github.com/EttusResearch/uhd/wiki/RFNoC:-Getting-Started

https://github.com/EttusResearch/uhd/wiki/RFNoC:--Specification