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diff --git a/_log/_site/etlas.html b/_log/_site/etlas.html deleted file mode 100644 index 06e3ce7..0000000 --- a/_log/_site/etlas.html +++ /dev/null @@ -1,103 +0,0 @@ -<p>Etlas is a news, stock market, and weather tracker powered by an ESP32 NodeMCU -D1, featuring a 7.5-inch <a href="https://www.waveshare.com/" class="external" target="_blank" rel="noopener noreferrer">Waveshare</a> 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 shows two weeks of end-of-day prices—the maximum the ESP32’s -SRAM can hold—from the Polygon.io API. The price feed is relayed through a -FastCGI-wrapped Flask app hosted on a VPS. This lets me configure stock symbols -in its application settings. The app cycles through them as requests come in -from the ESP32. Running the Flask app as a FastCGI process while exposing it -via httpd with htpasswd authentication keeps the server code simple and secure.</p> - -<p>The following diagram outlines the Etlas’s overall system architecture.</p> - -<p><img src="etlas_arch.png" alt="architecture" /></p> - -<p>The more prominent panel on the right of the display shows local and world news -from Channel NewsAsia. The MCU downloads and parses XML data from the RSS feed -directly before rendering it to the display. The character glyphs used are -stored as bitmaps in the sprites directory. I skipped the proxy for news to -avoid writing more server code, but in hindsight it limits the feeds Etlas can -handle. I will fix this in a future version.</p> - -<p>The middle and bottom right panels display the temperature and relative -humidity from the DHT22 sensor. The DHT22 uses pulse-width modulation to -transmit data to the host. The 26µs, 50µs, and 70µs pulses are too fast for the -ESP32 to measure reliably with standard APIs. Instead, the driver compares -relative pulse widths to differentiate zeros from ones:</p> - -<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>static inline int dht_await_pin_state(int state, int timeout) -{ - int t; - static const uint16_t delta = 1; - - for (t = 0; t < timeout; t += delta) { - ets_delay_us(delta); - if (gpio_get_level(DHT_PIN) == state) - return t; - } - return 0; -} - -static inline int dht_get_raw_data(unsigned char buf[DHT_DATA_LEN]) -{ - int rc; - unsigned char i, pwl, pwh; - - gpio_set_level(DHT_PIN, 0); - ets_delay_us(1100); - gpio_set_level(DHT_PIN, 1); - - if (!dht_await_pin_state(0, 40)) { - rc = 1; - xQueueSend(dht_evt_queue, &rc, (TickType_t) 0); - return 0; - } - if (!dht_await_pin_state(1, 80)) { - rc = 2; - xQueueSend(dht_evt_queue, &rc, (TickType_t) 0); - return 0; - } - if (!dht_await_pin_state(0, 80)) { - rc = 3; - xQueueSend(dht_evt_queue, &rc, (TickType_t) 0); - return 0; - } - - for (i = 0; i < DHT_DATA_LEN; i++) { - if (!(pwl = dht_await_pin_state(1, 50))) { - rc = 4; - xQueueSend(dht_evt_queue, &rc, (TickType_t) 0); - return 0; - } - if (!(pwh = dht_await_pin_state(0, 70))) { - rc = 5; - xQueueSend(dht_evt_queue, &rc, (TickType_t) 0); - return 0; - } - buf[i] = pwh > pwl; - } - return 1; -} -</code></pre></div></div> - -<p>I ported <a href="https://github.com/Fonger/ESP8266-RTOS-DHT" class="external" target="_blank" rel="noopener noreferrer">this</a> implementation from ESP8266 -to ESP32—all credit for the algorithm belongs to them.</p> - -<p>Etlas is a networked embedded system. All acquisition, processing, and -rendering of data are performed on the ESP32’s 160MHz microprocessor using less -than 512KB of SRAM. The embedded software that makes this possible is written -in C using ESP-IDF v5.2.1. The e-paper display driver is derived from Waveshare -<a href="https://github.com/waveshareteam/e-Paper" class="external" target="_blank" rel="noopener noreferrer">examples</a> for Arduino and STM32 -platforms.</p> - -<p>Etlas has been running reliably for over a year since August 2024.</p> - -<p>Files: <a href="source.tar.gz">source.tar.gz</a></p> |