Overview

We created a digital sound synthesizer that is capable of producing three different types of waveforms (sine, sawtooth, and triangle). Each waveform can be selected by pressing a pushbutton to cycle through the waveforms. A capacitive touch keypad provides the primary interface to select a note to play. An accelerometer on an IMU allows users to modulate the selected note. Additionally, a PWM-driven RGB LED displays the effect of the IMU.

Picture of Layout

Components

The following is a list of components used to build this project:

• 1 x mbed NXP LPC1768 Microcontroller
• 1 x MPR121 I2C Capacitive Touchpad
• 1 x LSM9DS1 IMU
• 1 x Class D Audio amplifier
• 1 x Breadboard compatible 8 Ohm Speaker
• 1 x Pushbutton
• 2 x 4.7k Ohm resistors
• 2 x 100 Ohm resistors
• 1 x 180 Ohm resistor

Wiring Connection Guide

MPR121 I2C 12 Key Capacitive Touchpad

*The I2C connections require pullup resistors to function properly*

LSM9DS1 IMU

Class D Audio Amplifier

RGB LED

To prevent the RGB LED from shorting, resistors are used to drop the current to each leg of the LED as shown below:

Pushbutton

Program Code

Here is a link to import the program.

Video