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NEW202402.TXT 

 

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>&lt;HTML&gt;
&lt;HEAD&gt;
  &lt;!-- AP: Last modified: 21-Jan-2016 --&gt;
  &lt;TITLE&gt;PWM&lt;/TITLE&gt;
&lt;/HEAD&gt;
&lt;BODY&gt;
&lt;P&gt;
&lt;SCRIPT&gt;
&lt;!-- 
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 &lt; data.length; i++) {
/* Prepare data */
//data[i] = (Math.random() - 0.5) * 2; // Noise
//data[i] = (i&gt;=samplesPerMilliSecond &amp;&amp; i&lt;pwm)? 2 : 0;
//data[i] = (i%samplesPerCycle&lt;pwm)? 2 : 0
data[i] = (i&lt;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(&quot;x&quot;,x,&quot;y&quot;,y ,&quot;y1l&quot;,y1l,&quot;y0l&quot;,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 &lt; data.length; i++) {
	  ctx.lineTo(i,canvas.height-data[i]*amp);
  };
  ctx.moveTo(i-1,canvas.height);
  ctx.stroke();
}




--&gt; &lt;/SCRIPT&gt;
&lt;H1&gt;
  &lt;A HREF=&quot;http://techref.massmind.org/Techref/language/html/HTML5webapps.htm">HTML5 web app&lt;/A&gt;
  &lt;A HREF=&quot;http://techref.massmind.org/Techref/io/pwm/index.htm">PWM</A> 
  &lt;A HREF=&quot;http://techref.massmind.org/Techref/io/servo/wav.htm">audio generator&lt;/A&gt;
  for &lt;A HREF=&quot;http://techref.massmind.org/Techref/io/servo/index.htm">Servo</A> 
  &lt;A HREF=&quot;http://techref.massmind.org/Techref/io/motors.htm">Motors</A>
&lt;/H1&gt;
&lt;P&gt;
Volume:
&lt;INPUT type=&quot;range&quot; min=0 max=100 oninput=&quot;
	onVolumeChange(parseInt(this.value, 10) / 100);
	displayWave(data,document.getElementById('scope'));
	displayWave(data2,document.getElementById('scope2'));
	&quot; value=2&gt;
&lt;INPUT type=&quot;button&quot; value=&quot;On&quot; onclick=&quot;onVolumeChange(1);
	displayWave(data,document.getElementById('scope'));
	displayWave(data2,document.getElementById('scope2'));
	&quot;&gt;
&lt;INPUT type=&quot;button&quot; value=&quot;Off&quot; onclick=&quot;onVolumeChange(0);
	displayWave(data,document.getElementById('scope'));
	displayWave(data2,document.getElementById('scope2'));
	&quot;&gt; 
&lt;BR&gt;
Ch1 Degrees: -90
&lt;INPUT type=&quot;range&quot; min=-90 max=90 oninput=&quot;
	onPWMChange(parseInt(this.value, 10));
	document.getElementById('degree').innerHTML=this.value;
	displayWave(data,document.getElementById('scope'));
	&quot; value=0&gt;+90
&lt;INPUT type=&quot;text&quot; min=-90 max=90 size=3 onchange=&quot;
	onPWMChange(parseInt(this.value, 10));
	document.getElementById('degree').innerHTML=this.value;
	displayWave(data,document.getElementById('scope'));
	&quot; value=0&gt; &lt;BR&gt;
Ch2 Degrees: -90
&lt;INPUT type=&quot;range&quot; min=-90 max=90 oninput=&quot;
	onPWMChange2(parseInt(this.value, 10));
	document.getElementById('degree2').innerHTML=this.value;
	displayWave(data2,document.getElementById('scope2'));
	&quot; value=0&gt;+90
&lt;INPUT type=&quot;text&quot; min=-90 max=90 size=3 onchange=&quot;
	onPWMChange2(parseInt(this.value, 10));
	document.getElementById('degree2').innerHTML=this.value;
	displayWave(data2,document.getElementById('scope2'));
	&quot; value=0&gt;
&lt;DIV id=&quot;degree&quot;&gt;
  0
&lt;/DIV&gt;
&lt;P&gt;
&lt;canvas id=&quot;scope&quot; width=&quot;200&quot; height=&quot;100&quot;&gt;&lt;/canvas&gt;
&lt;DIV id=&quot;degree2&quot;&gt;
  0
&lt;/DIV&gt;
&lt;P&gt;&lt;/P&gt;
&lt;canvas id=&quot;scope2&quot; width=&quot;200&quot; height=&quot;100&quot;&gt;&lt;/canvas&gt;
&lt;P&gt;&lt;/P&gt;
&lt;/BODY&gt;
&lt;/HTML&gt;</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 14:35, local time: 2024/11/8 14:32,
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