One noise source we observed was high frequency interference from the CPU with the analog input. We used a bandpass filter to exclude frequencies outside of this range. Since typical voice and instrument frequencies range between 100 Hz and 4,000 Hz, these are the low and high frequency cutoffs we desired for our input signal. The next step was to filter out the noise in the input signal. Once the output signal was significantly larger in amplitude, we noticed it was noisy. We decided to use an electret microphone for audio input, and were able to customize our gain and range of frequencies with a bandpass amplifier circuit. The audio signal was small and noisy, so we created an operational amplifier circuit that removed noise and amplified the signal. Overall schematic which includes connection details for the PIC32MX250F128B microcontroller, the 16x32 LED matrix, and the microphone circuit for amplifying and bandpassing the audio signal. We achieved a gain of 30 by setting R1 to 1 kΩ and R2 to 30 kΩ as shown in Figure 2.įIGURE 2. The output signal was very small, so we next decided to amplify the input.Īfter testing a range of gain values between 20 and 50, we determined that a gain of 30 was optimal because it was large enough to capture and amplify quieter sounds without causing the input signal to clip for louder sounds. We began with a simple microphone circuit and observed the output we were getting from playing music out loud. How exactly do we do this? The first crucial step was to acquire a nice clean audio signal. Music is input into the PIC32 as an audio signal.
This concurrency allows the PIC32 to run the project. Threads are independent processes that the PIC32 microcontroller switches between to run a small chunk of the process at a time. It appears to run all these tasks at the same time because of threads. High-level design flowchart of our music visualizer. The PIC32 is responsible for running various tasks required for the project: performing the analog-to-digital conversion on the audio signal output from the microphone circuit breaking this signal into its various frequency components and mapping these results to the LED matrix display ( Figure 1).įIGURE 1. Design of the Projectįirst off, let us introduce the brains behind the project: the PIC32 microcontroller. We then break the audio signal up based on its frequency and amplitude, and map the results to an LED matrix panel. We take sound as input into a microphone circuit which amplifies the audio signal and filters out noise. This is especially useful for people that are hearing impaired, as it allows them to experience music in a new way. Our music visualizer allows others to experience music through visual means not only is the display fascinating to look at, but it accurately picks up on the various frequencies that are being played. Our vision was to create a unit that listens to music being played, then in real time displays a dynamic and colorful visual representation of the music based on the volume and pitch of the notes. We wanted to design something fun, aesthetically pleasing, and interactive, and since we all enjoy listening to music, we decided on a music visualizer. As a final class project for our “Digital Systems Design Using Microcontrollers” course we all took last semester at Cornell University, we created a very unique device.
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