NOTE: This project is currently under construction.

Nexys 4 DDR Spectral Sources Demo

Features Used

Not Used Used
16 user switches X
16 user LEDs X
Two tri-color LEDs X
5 User Push Buttons X
Two 4-digit 7-segment displays X
4 Pmod ports X
Pmod for XADC signals X
12-bit VGA output X
Serial Flash for Application Data X
USB HID Host With Mouse X
USB HID Host With Keyboard X
Micro SD card connector X
PWM audio output X
PDM microphone X
3-axis accelerometer X
128MiB DDR2 X
Temperature sensor X
10/100 Ethernet PHY X


The Nexys4DDR gets PDM data from the built-in microphone, then digitally filters data for decimation and resolution (16 bit, 48KSPS). Then reverberates the audio data and outputs it to the built-in Audio Out, stores a frame of 1024 samples and shows it on a VGA display (640×480, 60Hz). then the demo computes the Fast Fournier Transform (FFT) of the stored data (512 bins x 46.875 Hz = 0…24KHz). The demo shows the first 80 FFT bins on the VGA display (80 bins x 46.875 Hz = 0…3.75KHz) and displays the first 30 FFT bins on an WS2812 LED string (30 bins x 46.875 Hz = 0…1.4KHz),



  • Basic familiarity with Vivado
    • This experience can be found by walking through our “Getting Started with Vivado” guide


  • Nexys 4 DDR FPGA board
  • Micro-USB cable
  • A 30 led strip of WS2812 LEDs (Not required for VGA operation)
  • Monitor with a VGA cable (Not required for WS2812 operation)


  • Vivado Design Suite 2015.X
    • Newer/older versions can be used, but the procedure may vary slightly


Spectral Sources Demo – ZIP

How to...

1. Generate the Project

1.1) Download the zip file linked in the download section and unzip it in the location of your choosing.
1.2) Generate the Nexys4DDRSectralSources project in the “proj” folder by following this guide before continuing: How to Generate a Project from Digilent's Github

2. Build the Project

2.1) Click Generate Bitstream on the left hand menu towards the bottom. Vivado will run through both Run Synthesis and Run Implementation before it generates the bitstream automatically.

Note: If you want, you can click each step by itself in the order of Run Synthesis, Run Implementation and then Generate Bitstream.

3. Program the Board

3.1) Once you have generated your bit file, Click on the hardware manager and connect to your board by choosing the local server option.

3.2) Click program to load the project onto your Nexys4-DDR.

4. Run the Project

This portion will help you run the demo and observe all its features.

4.1) Connecting the Leds

Connect the strip of WS2812 leds to the JC Pmod connector. The power and ground can go to the Pmod header 3v3 and ground ports while the LED data should connect to pin 4 on the header.

4.2) Connecting the VGA and Running the Demo

Connect the monitor to the VGA port of the Nexys4DDR and observe the audio data displayed on the screen.