View topic - ADXL335 accelerometer. KnockSensor. Learning Examples | Foundations | Hacking | Links Here we use a Piezo element to detect sound, what will allow us to use it as a knock sensor. We are taking advantage of the processors capability to read analog signals through its ADC - analog to digital converter. These converters read a voltage value and transform it into a value encoded digitally. In the case of the Arduino boards, we transform the voltage into a value in the range 0..1024. 0 represents 0volts, while 1024 represents 5volts at the input of one of the six analog pins. A Piezo is nothing but an electronic device that can both be used to play tones and to detect tones.
In our example we are plugging the Piezo on the analog input pin number 0, that supports the functionality of reading a value between 0 and 5volts, and not just a plain HIGH or LOW. The other thing to remember is that Piezos have polarity, commercial devices are usually having a red and a black wires indicating how to plug it to the board. Record and Playback Analog Sound. 2 x MCP4921 digital to analog converter / DAC. Digital-to-analog converter. 8-channel digital-to-analog converter Cirrus Logic CS4382 as used in a soundcard. DACs and their inverse, ADCs, are part of an enabling technology that has contributed greatly to the digital revolution.
To illustrate, consider a typical long-distance telephone call. The caller's voice is converted into an analog electrical signal by a microphone, then the analog signal is converted to a digital stream by an ADC. The digital stream is then divided into packets where it may be mixed with other digital data, not necessarily audio. The digital packets are then sent to the destination, but each packet may take a completely different route and may not even arrive at the destination in the correct time order.
DACs are commonly used in music players to convert digital data streams into analog audio signals. Overview[edit] Ideally sampled signal. Practical operation[edit] Piecewise constant output of an idealized DAC lacking a reconstruction filter. Applications[edit] Audio[edit] Video[edit] Playground - InterfacingWithHardware. Interface class for the Arduino Wave Shield. Using the Arduino Wave Shield ( was not easy and requires writing too much code. Therefore I have made an interface for it, the MediaPlayer class.
The class is very easy to use. You only have to add the MediaPlayer class to your project and add these three lines:#include "util.h"#include "MediaPlayer.h"MediaPlayer mediaPlayer; Now we can play WAV files by using functions as:play(), stop(), pause(), resume() etc. The class is idiot proof, it is allowed to use any erroneous combination of these functions, such as stop() before using play(). Use the MediaPlayerTest project to learn about all the opportunities of the MediaPlayer class. This is optional: the function blinkLed() requires on the wave shield card the onboard LED LED2, resistor R10 (470 ohm) and a wire between pin WP2 and digital I/O pin 6.
Procedure:Create a folder with the name “MediaPlayerTest” and add the 4 files to it. It is preferable to use the Atmega 328p, which has more memory. #endif. Lab3 - Laboratory for Experimental Computer Science. This is an experiment to show how some realtime audio processing can be done with the Arduino. The first set of examples alter an incoming audio signal and put it back to an audio output. We achieve effects like Reverb, Phasor, Flanger or Ringmodulator. The second set of examples are outputting computed waveforms like Sinewave, Bell and Xylophone sounds. Building and testing the Audio Circuit around the Arduino The audio input signal is connected via a 10uF capacitor to the the analog input 1 of the Arduino Board.
Two resistors and a trimmpot are adding an DC offset to the audiosignal . Software Concept The Software is divided into an interrupt function where the analog sampling an timing takes place and a main loop where the samples are processed an written back to the PWM as audio output. The main loop waits for the sample flag to be set by the interrupt. DC Offset A natural audiosignal consists of positive and negative waveparts which is leading to an electrical AC audiosignal. Forum. Audio Shield for Arduino.
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