Homepage mini simulation

.gitignore

@@ -23,6 +23,7 @@ distribute-*
 env/
 build/
 _build/
+OLD_build/
 dist/
 Sphinx.egg-info/
 doc/_build/

_static/js/homepage_app.js

@@ -0,0 +1,177 @@
+function homepage_app() {
+  function createSignal(N) {
+    const x = new Array(N * 2);
+
+    // complex AWGN
+    let noise_ampl_dB = document.getElementById("noise_ampl_dB").value;
+    document.getElementById("noise_value").innerHTML = noise_ampl_dB - 30;
+    let noise_ampl = Math.pow(10, noise_ampl_dB / 10);
+    for (let i = 0; i < N; i++) {
+      x[i * 2] = noise_ampl * Math.sqrt(-2.0 * Math.log(Math.random())) * Math.cos(2.0 * Math.PI * Math.random());
+      x[i * 2 + 1] = noise_ampl * Math.sqrt(-2.0 * Math.log(Math.random())) * Math.cos(2.0 * Math.PI * Math.random());
+    }
+
+    // Tone
+    let freq = document.getElementById("freq").value;
+    document.getElementById("freq_value").innerHTML = freq;
+    for (let i = 0; i < N; i++) {
+      x[i * 2] += Math.cos(2 * Math.PI * i * freq);
+      x[i * 2 + 1] += Math.sin(2 * Math.PI * i * freq);
+    }
+
+    return x;
+  }
+
+  const N = 1024;
+  let update_period = 50; // in ms, gets doubled every time refersh is too slow to keep up
+
+  function updatePlot() {
+    const start_t = performance.now();
+    const signal = createSignal(N);
+
+    const fft_obj = new FFT(N);
+    const signal_fft = fft_obj.createComplexArray();
+    fft_obj.transform(signal_fft, signal);
+
+    // Take magnitude of FFT
+    const signal_fft_mag = new Array(N);
+    for (let i = 0; i < N; i++) {
+      signal_fft_mag[i] = signal_fft[2 * i] * signal_fft[2 * i] + signal_fft[2 * i + 1] * signal_fft[2 * i + 1];
+    }
+    let signal_fft_mag_shifted = fftshift(signal_fft_mag);
+
+    // Convert to dB
+    const signal_fft_mag_shifted_dB = new Array(N);
+    for (let i = 0; i < N; i++) {
+      signal_fft_mag_shifted_dB[i] = 10 * Math.log10(signal_fft_mag_shifted[i]);
+    }
+
+    // Plot freq
+    const canvas = document.getElementById("freq_plot");
+    const ctx = canvas.getContext("2d", { alpha: false }); // apparently turning off transparency makes it faster
+
+    ctx.setTransform(1, 0, 0, 1, 0, 0); // resets transform
+    ctx.fillStyle = "white";
+    ctx.lineWidth = 1;
+    ctx.fillRect(0, 0, ctx.canvas.width, ctx.canvas.height);
+    ctx.translate(0, 400); // move half of canvas height so y=0 in middle
+    ctx.beginPath();
+    ctx.strokeStyle = "blue";
+    ctx.moveTo(0, Math.floor(-7 * signal_fft_mag_shifted_dB[0] + 200));
+    for (let i = 1; i < N; i++) {
+      ctx.lineTo(i * 2, Math.floor(-7 * signal_fft_mag_shifted_dB[i] + 200)); // -1* to flip y-axis
+    }
+    ctx.stroke();
+
+    // Freq x-axis ticks and labels
+    ctx.setTransform(1, 0, 0, 1, 0, 0); // resets transform
+    ctx.beginPath();
+    ctx.strokeStyle = "black";
+    ctx.lineWidth = 3;
+    ctx.font = "36px Arial";
+    ctx.fillStyle = "black";
+    // axis line
+    ctx.moveTo(0, ctx.canvas.height - 80);
+    ctx.lineTo(ctx.canvas.width, ctx.canvas.height - 80);
+    // ticks
+    for (let i = 0; i < 11; i++) {
+      ctx.moveTo((ctx.canvas.width / 10) * i, ctx.canvas.height - 100);
+      ctx.lineTo((ctx.canvas.width / 10) * i, ctx.canvas.height - 80);
+      ctx.fillText(Math.round((i - 5) * 0.1 * 100) / 100, ((ctx.canvas.width / 10) * i - 0) * 0.975, ctx.canvas.height - 35);
+    }
+    ctx.fillText("Hz", ctx.canvas.width / 2 + 5, ctx.canvas.height - 35);
+    ctx.fillText("Frequency", ctx.canvas.width / 2 - 70, ctx.canvas.height - 7);
+    ctx.stroke();
+
+    // Freq y-axis ticks and labels
+    ctx.setTransform(1, 0, 0, 1, 0, 0); // resets transform
+    ctx.beginPath();
+    ctx.strokeStyle = "black";
+    ctx.lineWidth = 3;
+    ctx.font = "36px Arial";
+    ctx.fillStyle = "black";
+    // axis line
+    ctx.moveTo(0, 0);
+    ctx.lineTo(0, ctx.canvas.height - 80);
+    // ticks
+    for (let i = 1; i < 6; i++) {
+      ctx.moveTo(0, ((ctx.canvas.height - 80) / 6) * i);
+      ctx.lineTo(20, ((ctx.canvas.height - 80) / 6) * i);
+      ctx.fillText(i * -10, 30, ((ctx.canvas.height - 80) / 6) * i + 10);
+    }
+    ctx.fillText("dB", 20, 36);
+    ctx.stroke();
+
+    // Plot time
+    const canvas_time = document.getElementById("time_plot");
+    const ctx_time = canvas_time.getContext("2d", { alpha: false });
+
+    ctx_time.setTransform(1, 0, 0, 1, 0, 0); // resets transform
+    ctx_time.fillStyle = "white";
+    ctx_time.lineWidth = 1;
+    ctx_time.fillRect(0, 0, ctx.canvas.width, ctx.canvas.height);
+    ctx_time.translate(0, 400); // move half of canvas height so y=0 in middle
+    ctx_time.beginPath();
+    ctx_time.strokeStyle = "blue";
+    ctx_time.moveTo(0, Math.floor(-20 * signal[0] - 40));
+    for (let i = 1; i < N; i++) {
+      ctx_time.lineTo(i * 2, Math.floor(-20 * signal[i * 2] - 40)); // -1* to flip y-axis
+    }
+    ctx_time.stroke();
+
+    // Time x-axis ticks and labels
+    ctx_time.setTransform(1, 0, 0, 1, 0, 0); // resets transform
+    ctx_time.beginPath();
+    ctx_time.strokeStyle = "black";
+    ctx_time.lineWidth = 3;
+    ctx_time.font = "36px Arial";
+    ctx_time.fillStyle = "black";
+    // axis line
+    ctx_time.moveTo(0, ctx_time.canvas.height - 60);
+    ctx_time.lineTo(ctx_time.canvas.width, ctx_time.canvas.height - 60);
+    // ticks
+    for (let i = 0; i < 11; i++) {
+      ctx_time.moveTo((ctx_time.canvas.width / 10) * i, ctx_time.canvas.height - 80);
+      ctx_time.lineTo((ctx_time.canvas.width / 10) * i, ctx_time.canvas.height - 60);
+      //ctx_time.fillText(Math.round(i* 0.1 * 100) / 100, ((ctx_time.canvas.width / 10) * i - 0) * 0.98, ctx_time.canvas.height - 5);
+    }
+    ctx_time.fillText("Time", ctx_time.canvas.width / 2, ctx_time.canvas.height - 5);
+    ctx_time.stroke();
+
+    // Time y-axis ticks and labels
+    ctx_time.setTransform(1, 0, 0, 1, 0, 0); // resets transform
+    ctx_time.beginPath();
+    ctx_time.strokeStyle = "black";
+    ctx_time.lineWidth = 3;
+    ctx_time.font = "36px Arial";
+    ctx_time.fillStyle = "black";
+    // axis line
+    ctx_time.moveTo(0, 0);
+    ctx_time.lineTo(0, ctx_time.canvas.height - 80);
+    // ticks
+    for (let i = 1; i < 6; i++) {
+      ctx_time.moveTo(0, ((ctx_time.canvas.height - 80) / 6) * i);
+      ctx_time.lineTo(20, ((ctx_time.canvas.height - 80) / 6) * i);
+    }
+    ctx_time.fillText("1", 20, 36);
+    ctx_time.fillText("-1", 20, ctx_time.canvas.height - 80);
+    ctx_time.fillText("0", 30, ctx_time.canvas.height / 2 - 40);
+    ctx_time.stroke();
+    // y=0 line
+    ctx_time.strokeStyle = "grey";
+    ctx_time.lineWidth = 1;
+    ctx_time.moveTo(0, (ctx_time.canvas.height - 80) / 2);
+    ctx_time.lineTo(ctx_time.canvas.width, (ctx_time.canvas.height - 80) / 2);
+    ctx_time.stroke();
+
+    //console.log("Time taken to update frame: " + (performance.now() - start_t) + " ms");
+    if (performance.now() - start_t > update_period) {
+      console.log("Warning: browser is not able to keep up, doubling update period");
+      update_period = update_period * 2;
+    }
+  }
+
+  setInterval(function () {
+    updatePlot();
+  }, update_period); // in ms
+}

_templates/homepage.html

@@ -6,44 +6,55 @@ <h1 style="text-align: center">PySDR: A Guide to SDR and DSP using Python</h1>
     <span class="std std-ref">Dr. Marc Lichtman</span>
   </a>
   -
-  <a
-    class="reference external"
-    href="mailto:pysdr&#37;&#52;&#48;vt&#46;edu"
-    rel="noopener noreferrer"
-    target="_blank"
-  >
+  <a class="reference external" href="mailto:pysdr&#37;&#52;&#48;vt&#46;edu" rel="noopener noreferrer" target="_blank">
     pysdr<span>&#64;</span>vt<span>&#46;</span>edu
   </a>
 </p>
 
 <h4 style="line-height: 1.4">
-  Welcome to PySDR, a free online textbook (not a Python library!) that provides a gentle introduction
-  to wireless communications and software-defined radio (SDR) using an abundance
-  of diagrams, animations, and Python code examples. From FFTs to filters to
-  digital modulation to receiving and transmitting from SDRs in Python, PySDR
-  has you covered!
+  Welcome to PySDR, a free online textbook (not a Python library!) that provides a gentle introduction to wireless communications and software-defined
+  radio (SDR) using an abundance of diagrams, animations, and Python code examples. From FFTs to filters to digital modulation to receiving and
+  transmitting from SDRs in Python, PySDR has you covered!
 </h4>
 
 <h4 style="line-height: 1.4">
-  The goal of PySDR is to increase accessibility to topics traditionally covered
-  in a math-intensive manner and within a relatively small set of universities.
-  All content used to generate PySDR is open source, and can be found
-  <a
-    class="reference external"
-    href="https://github.com/777arc/PySDR"
-    rel="noopener noreferrer"
-    target="_blank"
-    >here</a
-  >.
+  The goal of PySDR is to increase accessibility to topics traditionally covered in a math-intensive manner and within a relatively small set of
+  universities. All content used to generate PySDR is open source, and can be found
+  <a class="reference external" href="https://github.com/777arc/PySDR" rel="noopener noreferrer" target="_blank">here</a>.
 </h4>
 
 <h4>
   See
-  <a class="reference internal" href="content/intro.html#intro-chapter"
-    ><span class="std std-ref">Chapter 1: Introduction</span></a
-  >
+  <a class="reference internal" href="content/intro.html#intro-chapter"><span class="std std-ref">Chapter 1: Introduction</span></a>
   for the textbook's purpose and target audience.
 </h4>
+
+<h4>
+  To get a quick taste of RF signal processing, try playing with the simulation below which shows the frequency and time domain of a signal
+  consisting of a tone and white Gaussian noise.
+</h4>
+
+<div>
+  <input type="range" min="-0.4" max="0.4" step="0.0001" value="0.01" class="slider" id="freq" />
+  <span id="freq_value"></span>
+  <label>[Hz] - Tone Frequency</label>
+</div>
+<div>
+  <input type="range" min="-20" max="10" step="0.1" value="0" class="slider" id="noise_ampl_dB" />
+  <span id="noise_value"></span>
+  <label>[dB] - Noise Amplitude</label>
+</div>
+<div>
+  <canvas width="2048" height="800" id="freq_plot" style="width: 512px; height: 200px; border: 0px; image-rendering: auto"></canvas>
+</div>
 <br />
+<br />
+<div>
+  <canvas width="2048" height="800" id="time_plot" style="width: 512px; height: 200px; border: 0px; image-rendering: auto"></canvas>
+</div>
+
+<script>
+  homepage_app();
+</script>
 
-DEMO
+<br />

conf.py

@@ -266,7 +266,8 @@ def setup(app):
 html_js_files = [
     'js/beamforming_slider_app.js',
     'js/FFT.js',
-    'js/cyclostationary_app.js'
+    'js/cyclostationary_app.js',
+    'js/homepage_app.js'
 ]
 
 # Add any extra paths that contain custom files (such as robots.txt or