Theory of Operation
This Business card functions as a Bluetooth speaker utilizing an ESP32 as the main Bluetooth controller. Utilizing the I2S peripherals to then feed into a MAX98357 audio amplifier which will connect to 2 surface mount speakers on the board to play music!
I wanted to add a little more pizazz to the board than just music, so I then had the idea to have lights on it that modulate to the Bass, Mind band, and Treble of the audio. The lights are controlled using the LM3914 Dot/Display Driver, which utilizes a comparater ladder to compare voltage levels and turn on the corresponding LEDs
Bluetooth Speaker and Audio Amplifier
The Bluetooth speaker portion of the build is the easier part as I only utilized a small example code for Bluetooth audio from
LED Light Modulation
I wanted the Lights to Modulate appropriately to the Bass, Mid Band, and Treble frequencies to give off a cool effect for when the music is playing.
Low Pass Filter : Bass Frequencies
Bass Frequency Range is achieved with an Active Low Pass Filter with a cut-off frequency of 500Hz . The Gain values I left as unity for the time being as it will require some tuning to get the desired amplitude range to modulate the LEDs. The High Pass filter is Similar in concept.
High Pass Filter : Treble Frequencies
The High Pass filter is Similar in concept just with different values and the gain to be similar tuned once on the board.