terfaced Machine Operating Network (SIMON)

The purpose of Sign-Interfaced Machine Operating Network, or SIMON, is to translate sign language into numbers. We used a machine learning classifier to classify images of hands into the corresponding symbols or actions. SIMON interprets American Sign Language and displays the translation on the LCD screen through the following steps. The given image of the ASL sign was extracted to produce a single numerical digit using a machine learning model. That value was then serialized to ASCII and sent to the microcontroller. The microcontroller would deserialize the value and post the result to the LCD screen. Hardware used to complete this project included the ATMega328P Xplained Mini Board, a laptop with Windows, a webcam, and an LCD screen. The goal of final project was achieved as we were successfully able to read the American Sign Language images and display the desired result on the LCD screen.

8-Button Piano – The Big Picture

The principal goal of our project was to design and build an 8-button piano & music player – two different implementations of the same circuit. As a piano, our circuit utilizes the attached buzzer to generate tones C6 through C7; this was achieved through the use and development of an interrupt driven system. Once the button is pressed, the corresponding LED illuminates and its given tone plays through the buzzer. As a music player we utilized the same buttons, instead once the button is pressed and the LED is lit, the buzzer begins to play a pre-programmed song. These tunes utilize the same tone generation in the piano. We were able to accomplish both programs for our circuit by writing and debugging in the C programming language within Atmel Studio 7.0.



Furthermore, we continued to use the Xplained Mini ATMega328P microcontroller from the previous labs in our final project implementation. We faced several setbacks when implementing our planned design including, but not limited to, configuring the GPIO pins to accept an input from the buttons, eliminating the rotary switch, and generating a tone from the connected buzzer. Nevertheless, we were able to overcome these hurdles and implement our design as intended with only small modifications to the circuit and code.

Temperature Controlled Fan – Overview

The idea for this project was to build an enclosed device that would actively attempt to cool itself as temperatures inside increased. The main components for the project were the ATmega328P Xplained Mini microcontroller, a temperature sensor, and a 5 volt DC fan. The device was placed into a small plastic enclosure. A circular hole was cut into the top to mount the fan, a rectangle was cut to fit an LCD screen for displaying the temperature, and two rectangles were cut on the side for ventilation and USB power. This project utilized variations of analog to digital conversion (ADC) from Lab 3 and pulse width modulation (PWM) from Lab 4.

The ADC on the microcontroller was used to convert readings from the temperature sensor into a temperature value. A separate temperature value was set as a target temperature. As the temperature inside the case increased beyond the target temperature, the fan would switch on to ventilate the hot air out of the case to cool it down. Additionally, a transistor was used along with PWM via the board’s Timer Counter 1 and Compare Match Interrupt to limit the voltage to the fan and control its speed. The fan would start at a 40 percent duty cycle and increase by 10 percent for every degree above the target temperature, maxing out at a 100 percent duty cycle. Conversely, the fan would decrease its duty cycle as the temperature decreased, turning back off after reaching below the target temperature.

Top View of the Case

Inside View of the Case


Plant Watering System – Overview

Hello Embedded Systems Fans!

It’s that time of the year – finals! Which means it’s time for our final project. The Unknowns were working night and day trying to decide what project we wanted to do, when it dawned on us…. we’d forgotten to water out plants!

Luckily, they were able to be saved, but it sparked the idea; “what if there were a system which would figure out when our plants needed watering, and would do it for us?” And so came about the big idea for our final project – an automatic plant waterer! All we would need is our handy-dandy Atmega328P Xplained Mini, a motor driver, a water pump, and a soil moisture sensor (shown below). 

Follow The Unknowns though our plant watering journey!



Spinning LED Display – The Big Picture

This project dealt with timing, frequency, and the phenomenon of persistence of vision. The project required a platform for spinning the display, the display, and the code to run the display.

The base platform is made from sections of 2×4 which provide a sturdy mounting point for the rest of the apparatus. The motor used to spin the LED’s platform is mounted on the wood base. Two ATMega328P boards are used, one for the motor and one for the LEDs. The LEDs are mounted in a breadboard on a separate section of light wood. The light wood and attached components all spin with an external battery allowing for two separate sections of the project.

Successfully getting the persistence of vision words displaying correctly required significant tuning to get the right timing. Another challenge was balancing the spinning section which was solved with weights on the opposite end. The complete product works and demonstrates the fascinating nature of persistence of vision.

An application was also made in the Unity Engine to help generate the necessary characters in a reasonable amount of time.

Boogie Ball Overview

This project centers around Audio Visual Equalizers and modifying it to be in the shape of a sphere/disco ball.

The design of the disco ball is 6 arches of wood, surrounding a main center column thus creating the outline of a sphere. The base of the disco ball was then constructed in a way to be able to accomodate the Xplained mini. The wooden arches were then layered with WS2812B Neopixel LED strips. Each strip can be individually addressed thus allowing for a viewer to see seperate audio frequencies. The splitting of the signal into seperate frquencies was handled via the code, utilizing the AdafruitNeopixel library to handle the lights and AdaFruitCITiCoServo libray to handle the hysical movement.

Several adjustments/customizations could be made when using the project such as the brightness and color of the lights, the speed of the rotation and, of course, the actual song being played.

Boogie Ball: Code Snippet

The ball’s rotation is done through the implementation of a Timer Compare Interrupt. Each time this interrupt occurs, a global flag is set in the code. The main program loop checks this flag each loop and updates the servo position each time it is set. The flag is then cleared and the loop continues until the interrupt occurs again. A snippet of the code that changes the servo position is shown below along with a video of the spinning.

Continue reading Boogie Ball: Code Snippet

Boogie Ball – Schematic

WS2812B Neopixels were used for this project. These LEDs contain an IC that allows for each LED to be individually addressable. This is ideal for showing the volume of each individual frequency band by turning on additional LEDs as volume increases.



The MSGEQ7 chip is a CMOS IC that is essential for audio equalization. Using an audio input, the chip splits the frequency spectrum into a set of 7 frequency bands. After the passband filters divide the spectrum into the seven bands, peak detectors establish the DC values that will be passed when a multiplexed band is selected. The DC output is then sent to the microcontroller through IC pin 3.





The bands are read by reading the lowest frequency band and passing a DC value to the microcontroller. The chip Strobes and the next frequency band is read on the rising edge. This is continued until all 7 bands have been read. The chip is then Reset.

To build the circuit, the msgeq7 datasheet revealed the supporting resistors and capacitors needed externally to use the chip. This simply consisted of a filtering capacitors and current limiting resistors placed throughout the circuit. Below is a capture taken straight from the msgeq7 datasheet. It contains the suggested hardware implementation for utilizing the chip.

After creating the schematic, each pin was referenced to a specific pin on an Arduino Uno. This microcontroller has the same microprocessor and pinout, but also has much more open-source support. Below is the schematic our team created for tying the msgeq7 chip circuitry into an arduino uno pinout to match the Xplained Mini board.

To create the printed circuit board (PCB) layout, contained a library with an Arduino Uno body with correctly placed headers. This allowed for the msgeq7 circuitry to be placed onto the forked Uno layout. The final result is an equalizer shield for an Arduino Uno that has stereo inputs. The top copper of the single sided PCB was poured to connect a common ground for the schematic. This allowed for maximum heat dissipation as well as fewer traces to map. Below is the PCB layout our team created for our equalization board. This allows the user to use this board as a shield for the Xplained Mini or an Arduino Uno.


8-Button Piano – Interrupt Driven Code

Our 8-Button Piano is driven purely by interrupts. Utilizing the in-class example for button handling, we configured all 8 of our buttons as input using the GPIO ports available on the ATMega328P Xplained Mini microcontroller. In order to achieve a level of attainable modularity with our design, we utilized predefined macros to indicate the data direction register, port, and pin numbers for each of our buttons.  Continue reading 8-Button Piano – Interrupt Driven Code

8-Button Piano – Schematics

When coming up with the design of the piano, we wanted to be able to cover one octave of naturals, the white keys on a piano, and be able to change the octave that is being played, as a standard piano has seven. As such, we would need eight pushbuttons to serve as our keys and either a seven or eight position rotary switch to be able to change the octave. LEDs were also implemented after the switches to show the user which tone is played from the buzzer.

The switch and LED series was created by putting 5V on one leg of the switch and a 220Ω resistor on the opposite corner. This resistor is then in series with the anode of the LED and a wire connecting to the ATMega328P board. Another 220Ω resistor is placed between the cathode of the LED and connected to ground. The configuration of the LED is key as current can only flow from the anode to the cathode of a diode. In the initial design, there was not a resistor between the cathode and ground. The LED would light up, but a sound would not consistently come from the buzzer. Placing the second resistor resulted in a tone being played every time the button was pressed. The LED also served to let us know when the tone would be played. The signal that the board receives from pressing the button is a square wave with either a value of 1 or 0. The LED is on when the value is 1 and off when it is 0, the speaker plays the tone during the falling edge of the wave. In other words, when the wave drops from 1 to 0, the proper tone is played. These are all plugged into pins PD0-PD7.