Freescale H.I.T. Project # 2: MonkeyListen - A DIY Audio Spectrum Analyzer Display

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Freescale H.I.T. Project # 2: MonkeyListen - A DIY Audio Spectrum Analyzer Display

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Freescale H.I.T. Project # 2: MonkeyListen - A DIY Audio Spectrum Analyzer Display

Project Summary

SheldonListen.bmpMonkeyListen uses the FRDM-K20D50 board (which has a Cortex M4 core with DSP instructions) with the FRDM-OLED shield so you can  make your very

own spectrum analyzer display  The end result will be a functional DSP system that will analyze incoming audio content via an electret microphone on FRDM-OLED board and display the spectral content.   The example code will also show you how to plot time domain data (a simple audio scope!),  Frequency domain data (via an FFT) and a time-frequency plot (spectrogram).  Extra I/O are provided to hack the code and create your own DMM or oscilloscope. The FRDM-OLED shield also has an optional RS-485 interface for doing cool things like driving a DMX lighting system!

Skills Developed:

  • Spectral Analysis via FFT
  • OLED display interfacing
  • Electret microphone Interfacing
  • Soldering SOIC8 and 1206 surface mount devices
  • Cortex CMSIS DSP Library






Development Tools

Install Codewarrior 10.5 for Microcontrollers (Eclipse)

Special Edition to your  machine

Example Code

Get the latest copy from Github

Prerequisite Videos:

All of the videos are organized on a Youtube playlist: H.I.T. #2: MonkeyListen - YouTube

  • MonkeyListen WatchMe1st
  • MonkeyListen Demo: Time Domain + FFT Mode
  • MonkeyListen Demo: Spectrogram Mode
  • Spectral Analysis for Embedded Systems Part 1 & Part 2
  • Getting Started with the ARM CMSIS DSP FFT library
  • Introduction to Fixed Point Math for Embedded Systems Part 1, 2 and 3
  • The q31_t (Q.31) number format for the CMSIS DSP libraries
  • FRDM-OLED Overview
  • EEVblog #611 - Electret Microphone Design
  • Loading and Configuring the MonkeyListen Example Software

Step 1:  Get a FRDM-OLED

     You can order raw PCBs yourself from OSHPark or your favorite PCB vendor.      The bill of materials for the FRDM-OLED is included with the build package on the FRDM-OLED page.     Please let us know if you are interested in a pre-assembled version.   If there is enough demand we will get some built via a Kickstarter campaign   Don't be afraid to build it yourself,  Soldering is fun!  There is plenty of good stuff on the web on how to do SMT soldering.   All of the parts on the board are fairly simply once you get the hang of it and everything can be hand soldered  The key is having some decent tools.

Step 2: Put it Together

Attach  The FRDM-OLED to the FRDM-K20D50.   The FRDM-K20D50 comes with female headers that you can solder on so the boards can be easily separated.

Step 3: Download

Download the example software.   The video "Loading and Configuring the MonkeyListen Example Software" will step you though downloading the program and doing some basic configuration.

Step 4: Say Something

Speak, Sing and Yell....

Step 5: Hack!

Do something else cool.....  Make a DMM,  or an o-scope....

Version history
Revision #:
1 of 1
Last update:
‎03-24-2014 08:41 AM
Updated by: