Christine and Shela‘s final project for the ECE4760 (Digital Systems Design Using Microcontrollers) class they took this fall was a Bluetooth controlled car with a dedicated remote control device. The car and the remote both uses Atmega1248P microcontrollers and HC-05 Bluetooth transceiver modules. The remote also consists of a MPU-6050 gyroscope/accelerometer module on board to sense the tilting angle of the remote. Once the two Bluetooth units are paired, the remote control device continuously sends out the tilt angle data to the car. The Atmega1248P on board the car then linearly maps the tilt angles to the the duty cycles of the PWM signals controlling the motors, thus varying the speed according to the tilt angle. Based on the direction you tilt the remote, the car will also move to forward, backward, left and right directions.
Bluetooth controlled car with a remote
Watch the car in action below.
A sound spectrogram is a visual representation of the frequency components contained in an audio signal. The device that generates the spectrogram is called spectrograph. In a spectrogram, the horizontal axis is time and the vertical axis represents frequency. The spectrogram is color coded or gray-scaled to represent the relative intensity of the sound in each frequency region and time. Some of the applications of spectrograms are speech analysis and enhancement, studying bird and animal calls, music formation, etc. During pre-computer era, the spectrograms were generated using analog techniques that involved a series of bandpass filters. With the advent of digital signal processing, the most common approach of doing sound spectrography these days is through Fast Fourier Transform (FFT) of the time domain audio signal. Varun, Hyun, and Madhuri are EE students at Cornell and they have implemented a FFT-based real-time sound spectrography using two Atmega1284 processors as their final project for the ECE4760 Digital Systems Design Using Microcontrollers class. The two processors have different responsibilities. The first one is a dedicated audio processor, which receives the input audio signal from a 3.5mm audio jack or microphone, digitize it, and convert it into frequency domain using a 128-point FFT. The second processor is in charge of receiving the FFT data from the Audio processor and generating and outputting a real-time 4-bit grayscale histogram on a TV screen in real-time. Tact switch inputs are also implemented to allow the user to control play/stop, or to change the scrolling speed and the vertical scaling of the display.
Real-time sound spectrography using Atmega1284
Here is their demo video.