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+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8">
+    <title>Etlas: e-paper display for news, stocks, and the weather</title>
+    <head>
+<meta charset="utf-8">
+  <title>Etlas: e-paper display for news, stocks, and the weather</title>
+  <link rel="stylesheet" href="/assets/css/main.css">
+  <link rel="stylesheet" href="/assets/css/normalize.css">
+  <link rel="stylesheet" href="/assets/css/skeleton.css">
+</head>
+
+
+  </head>
+  <body>
+
+    <div class="container">
+  <ul id="navlist" class="left">
+    <li >
+      <a href="/">hme</a>
+    </li>
+    <li >
+      <a href="/projects/">tnk</a>
+    </li>
+    <li >
+      <a href="/about/">abt</a>
+    </li>
+    <li><a href="/feed.xml">rss</a></li>
+  </ul>
+</div>
+
+
+
+    <main>
+      <div class="container">
+        <h2 class="brand center" id="title">ETLAS: E-PAPER DISPLAY FOR NEWS, STOCKS, AND THE WEATHER</h2>
+
+        <h6 class="center">05 SEPTEMBER 2024</h5>
+
+        <br>
+
+        <div class="threecol justify"><p>Etlas is a news, stock market, and weather tracker powered by an ESP32 NodeMCU
+D1, featuring a 7.5-inch Waveshare e-paper display and a DHT22 sensor module.</p>
+
+<table style="border: none;">
+  <tr style="border: none;">
+    <td style="border: none;"><img src="dash.jpg" alt="front" style="width: 100%" /></td>
+    <td style="border: none;"><img src="pcb.jpg" alt="back" style="width: 100%" /></td>
+  </tr>
+</table>
+
+<p>The top left panel displays the end-of-day stock prices from the Polygon.io API, relayed through my own
+FastCGI-wrapped Flask app hosted on a VPS. The stock symbols can be configured
+through the Flask app’s application settings. The server.fcgi script enclosed
+in the tarball at the end of the page contains the Flask app.</p>
+
+<p>The following diagram outlines this system architecture.</p>
+
+<p><img src="etlas_arch.png" alt="architecture" /></p>
+
+<p>Unlike my <a href="/projects/e-reader">e-reader</a>, which worked with raster images,
+Etlas downloads time series data as CSV and computes the price curves on the
+ESP32.</p>
+
+<p>The more prominent panel on the right of the e-paper display shows local
+(Singapore) and world news from the Channel News Asia RSS feed. The MCU
+downloads and parses XML data from the RSS feed directly before rendering it to
+the display. Although I did it this way to avoid writing server code, it limits
+the feeds from which Etlas can receive data. In a future version, I will relay
+the RSS feed through a server (like the stock prices) to make it more flexible.</p>
+
+<p>The bottom panels (middle and right) display the temperature and relative
+humidity from a DHT22 sensor. The DHT22 driver, arguably the most interesting
+part of the software, reads real-time sensor data by comparing relative pulse
+widths. The pulses themselves are too quick for the ESP32 to reliably measure
+directly. I ported this
+implementation for ESP8266 modules to my ESP32. All credit for the algorithm
+belongs to them.</p>
+
+<p>Much of the heavy lifting of acquiring, interpreting, and rendering data from
+different data sources is performed on the microcontroller using less than 512
+KB of memory. The embedded software that makes that possible is written in C
+using the ESP-IDF v5.2.1. My e-paper display driver is a port of Waveshare examples for Arduino
+and STM32 platforms.</p>
+
+<p>I’ve been using Etlas daily (for a couple of hours on weekdays and all day on
+weekends) since August 2024. As of October 2025, it’s been running reliably for
+over a year. If you are interested in an e-paper display like this, drop me an
+email at the address on my home page.</p>
+
+<p>Files: <a href="source.tar.gz">source.tar.gz</a></p>
+</div>
+
+        <p class="right italics">by W. D. Sadeep Madurange</p>
+      </div>
+    </main>
+
+  </body>
+</html>