Step 5: Port a Model Composer Design to System Generator - 2020.2 English

Vivado Design Suite Tutorial: Model-Based DSP Design using Add-on for MATLAB and Simulink (UG1498)

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2020.2 English
Using Model Composer, you can package a model for integration into a System Generator model, which is especially useful if you are an existing System Generator for DSP user. This allows you to take advantage of both the high level of abstraction and simulation speed provided by Model Composer for portions of your design, and the more architecture-aware environment provided by System Generator.
Figure 1. System Generator Export Type

Choosing System Generator as the Target, and clicking Generate, creates a synthesized RTL block that you can directly add to a System Generator design using the Vitis HLS block in System Generator.

In this lab, you create an IP using Model Composer and then use the synthesized RTL as a block in a System Generator design.

  1. In the ModelComposer_Tutorial/Lab5/ModelComposer_to_SysGen folder, double-click MoC_design.slx to see the Model Composer design. The design is configured to have AXI4-Stream interfaces at both the input and output. This is done through the Interface Spec block within the ModelComposerDesign subsystem. Note that there are no structural changes required at the Simulink level to change interfaces for the IP.

  2. Open the followme_script.m in MATLAB. This script will guide you through all the steps to import the Model Composer generated solution as a block in System Generator.
  3. Read the comments at the start of each section (labeled Section 1 to Section 8) in the MATLAB script and execute each section one at a time (the start of each section is marked by a %% sign). You can click on Run and Advance to step through each section in the script. The sections are as follows:
    1. Section 1: Set up

      Open MATLAB for Model Composer and choose a video file as an input.

      video_filename = 'vipmen.avi';
      v = VideoReader(video_filename);
      frame_height = v.Height;
      frame_width = v.Width;
      save video_handle v
    2. Section 2: Creating a System Generator solution from a Model Composer design.

      Model Composer allows you to export a design as a block into System Generator. The result of exporting a design from Model Composer to System Generator is a solution folder that you will import into the System Generator design using the Vitis HLS block in System Generator.

    3. Section 3: Serializing the input video

      Serialize the input video which is required for use with the System Generator design which will do pixel-based processing.

      stream_in = zeros(ceil(v.FrameRate*v.Duration*v.Height*v.Width),1);
      i = 1;
      while hasFrame(v)
          frame = rgb2gray(readFrame(v));
          a = reshape(frame',[],1);
          stream_in(i:i+length(a)-1) = a;
          i = i + length(a);
      save stream_in stream_in
    4. Section 4: Import the generated solution into System Generator

      Set up the Vivado HLS block in the System Generator design to point to the correct solution folder generated in Section 2.

    5. Section 5: Simulate the System Generator Design

      Simulate the System Generator design and save the outputs into a MAT file. Note that the simulation will be slower than the Model Composer design since we are simulating the generated RTL and are doing an element-by-element based processing.

    6. Section 6: De-serializing the output of the System Generator design.

      This is a post-processing step that creates a frame-based video for playback using the outputs logged from the System Generator simulation.

      load stream_out
      load video_handle
      disp(['Length of input stream is ',num2str(length(stream_in))])
      disp(['Lenght of output stream is ',num2str(length(stream_out))])
      outputVideo = VideoWriter('stream_out.avi');
      outputVideo.FrameRate = v.FrameRate;
      The output is Boolean. This is why we multiply the img by 255, so that implay shows the image. 
      for i = 1:length(stream_out)/v.Height/v.Width
         img = reshape(stream_out((i-1)*v.Height*v.Width+1:i*v.Height*v.Width),v.Width,v.Height);
    7. Section 7: Play the de-serialized output using implay.
  4. The AXI4-Stream uses three signals, DATA, READY, and VALID. The READY signal is a back pressure signal from the slave side to the master side indicating whether the slave side can accept new data.

    As you examine the System Generator model in Section 4, pay attention to the labels on blocks for each signal to help you understand how the model is designed. For example, whenever the IP can no longer accept input, the READY signal (top right of the Vitis HLS block) puts pressure on the master side of the input AXI FIFO by resetting the READY signal. Likewise, the input AXI FIFO pressures the input stream by resetting its READY signal.

    Note: In Simulink all the inputs to a block are to one side of the block, and all the outputs are on the opposite side. As such, all the slave or master signals are not bundled together on one side of the block as you might expect.