ON 20240202@2:26:47 PM at page:
On a web page you were interested in at:
http://techref.massmind.org/Techref/io/servo/wav.htm#45324.6019328704
James Newton[JMN-EFP-786] Code:
<PRE><HTML>
<HEAD>
<!-- AP: Last modified: 21-Jan-2016 -->
<TITLE>PWM</TITLE>
</HEAD>
<BODY>
<P>
<SCRIPT>
<!--
var sampleRate = 96000;
var samplesPerMilliSecond = sampleRate*0.001;
var samplesPerCycle = samplesPerMilliSecond * 3;
var bufferLength = samplesPerCycle; //buffer one cycle
var context = new AudioContext(); //used to be webkitAudioContext();
var buffer = context.createBuffer(2, bufferLength, sampleRate);
var data = buffer.getChannelData(0);
var data2 = buffer.getChannelData(1);
// Done: adjust samplesPerCycle to be an even multiple of the bufferLength
var degrees = 0;
function buildPWMWav(degrees, samplesPerMilliSecond, data) {
var pwm = (degrees+90)/180*samplesPerMilliSecond+samplesPerMilliSecond;
for (var i = 0; i < data.length; i++) {
/* Prepare data */
//data[i] = (Math.random() - 0.5) * 2; // Noise
//data[i] = (i>=samplesPerMilliSecond && i<pwm)? 2 : 0;
//data[i] = (i%samplesPerCycle<pwm)? 2 : 0
data[i] = (i<pwm)? 2 : 0
};
}
onPWMChange = function (degrees) {
buildPWMWav(degrees, samplesPerMilliSecond, data);
};
onPWMChange2 = function (degrees) {
buildPWMWav(degrees, samplesPerMilliSecond, data2);
};
onPWMChange(0); //start in the center.
onPWMChange2(45); //start offcenter.
var source = context.createBufferSource();
source.loop = true; // Make sure that sound will repeat over and over again
source.buffer = buffer; // Assign our buffer to the source node buffer
gainNode = context.createGain();
//connect the source to the gainNode, and the gainNode to the destination.
source.connect(gainNode);
gainNode.connect(context.destination);
scale2log = function (x) {
let x0 = 0, x1 = 1
let offset = 0.0125
let y0 = 0+offset, y1 = 1+offset
let y1l = Math.log(y1)
let y0l = Math.log(y0)
let y = Math.exp((x * y0l - x * y1l + x0 * y1l - x1 * y0l) / (x0 - x1))
y = y-offset //remove the offset
y = Math.round(y * 1000) / 1000 //round off
//console.log("x",x,"y",y ,"y1l",y1l,"y0l",y0l)
return y
}
onVolumeChange = function (vol) {
context.resume();
gainNode.gain.value = scale2log(vol);
//console.log(Math.floor(gainNode.gain.value * 100));
};
onVolumeChange(0); //set initial volumn to zero
source.start(0);
//Just start immediatly with zero volume.
//Set volume to 0 to stop. If you use noteOff to stop,
//you have to recreate the source.
displayWave = function(data,canvas) {
var ctx = canvas.getContext('2d');
var amp = Math.min(64*gainNode.gain.value,99)+10;
canvas.width = data.length+10;
ctx.fillStyle = 'white';
ctx.fillRect(0,0,canvas.width,canvas.height);
ctx.strokeStyle = 'red';
ctx.beginPath();
ctx.moveTo(0,canvas.height);
for (var i = 0; i < data.length; i++) {
ctx.lineTo(i,canvas.height-data[i]*amp);
};
ctx.moveTo(i-1,canvas.height);
ctx.stroke();
}
--> </SCRIPT>
<H1>
<A HREF="http://techref.massmind.org/Techref/language/html/HTML5webapps.htm">HTML5 web app</A>
<A HREF="http://techref.massmind.org/Techref/io/pwm/index.htm">PWM</A>
<A HREF="http://techref.massmind.org/Techref/io/servo/wav.htm">audio generator</A>
for <A HREF="http://techref.massmind.org/Techref/io/servo/index.htm">Servo</A>
<A HREF="http://techref.massmind.org/Techref/io/motors.htm">Motors</A>
</H1>
<P>
Volume:
<INPUT type="range" min=0 max=100 oninput="
onVolumeChange(parseInt(this.value, 10) / 100);
displayWave(data,document.getElementById('scope'));
displayWave(data2,document.getElementById('scope2'));
" value=2>
<INPUT type="button" value="On" onclick="onVolumeChange(1);
displayWave(data,document.getElementById('scope'));
displayWave(data2,document.getElementById('scope2'));
">
<INPUT type="button" value="Off" onclick="onVolumeChange(0);
displayWave(data,document.getElementById('scope'));
displayWave(data2,document.getElementById('scope2'));
">
<BR>
Ch1 Degrees: -90
<INPUT type="range" min=-90 max=90 oninput="
onPWMChange(parseInt(this.value, 10));
document.getElementById('degree').innerHTML=this.value;
displayWave(data,document.getElementById('scope'));
" value=0>+90
<INPUT type="text" min=-90 max=90 size=3 onchange="
onPWMChange(parseInt(this.value, 10));
document.getElementById('degree').innerHTML=this.value;
displayWave(data,document.getElementById('scope'));
" value=0> <BR>
Ch2 Degrees: -90
<INPUT type="range" min=-90 max=90 oninput="
onPWMChange2(parseInt(this.value, 10));
document.getElementById('degree2').innerHTML=this.value;
displayWave(data2,document.getElementById('scope2'));
" value=0>+90
<INPUT type="text" min=-90 max=90 size=3 onchange="
onPWMChange2(parseInt(this.value, 10));
document.getElementById('degree2').innerHTML=this.value;
displayWave(data2,document.getElementById('scope2'));
" value=0>
<DIV id="degree">
0
</DIV>
<P>
<canvas id="scope" width="200" height="100"></canvas>
<DIV id="degree2">
0
</DIV>
<P></P>
<canvas id="scope2" width="200" height="100"></canvas>
<P></P>
</BODY>
</HTML></PRE>
ON 20240202@2:28:39 PM at page:
On a web page you were interested in at:
http://techref.massmind.org/Techref/io/servo/wav.htm#
James Newton[JMN-EFP-786] edited the page. Difference:
http://techref.massmind.org/techref/diff.asp?url=\Techref\io\servo\wav.htm&version=1
ON 20240202@2:35:28 PM at page:
On a web page you were interested in at:
http://techref.massmind.org/Techref/io/servo/html4audiopwm.html#
James Newton[JMN-EFP-786] edited the page. Difference:
http://techref.massmind.org/techref/diff.asp?url=\Techref\io\servo\html4audiopwm.html&version=1
| file: /Techref/new202402.txt, 6KB, , updated: 2024/2/2 15:35, local time: 2024/7/26 20:49,
3.145.92.29:LOG IN
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