Etlas.

1 files changed, 28 insertions, 38 deletions

diff --git a/_log/etlas.md b/_log/etlas.md
index c274401..cc45ea4 100644
--- a/_log/etlas.md
+++ b/_log/etlas.md
@@ -6,41 +6,34 @@ project: true
 thumbnail: thumb_sm.jpg
 ---
 
-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.
+Repurposed [e-reader prototype](../e-reader/) into something for regular use.
+News, stocks, weather dashboard.  ESP32 NodeMCU D1 + 7.5" Waveshare e-paper +
+DHT22 sensor.
 
 <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>
+  <tr style="border: none;">
+    <td colspan="2" style="border: none;"><img src="etlas_arch.png" alt="front" style="width: 100%"></td>
+  </tr>
 </table>
 
-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.
+Stocks: Two weeks EOD prices from Polygon.io (max SRAM holds). Flask app on VPS
+relays feed, lets me swap symbols via config. FastCGI + httpd + htpasswd.
 
-The following diagram outlines the Etlas's overall system architecture.
+gui_plot_stocks() is CPU heavy and triggers the WDT. vTaskDelay() prevents
+that. Stepped graph easier to code for the bit-packed framebuffer (especially
+under current memory constraints), but its messy--too messy.
 
-![architecture](etlas_arch.png)
+Note to self: Refactor gui_plot_stocks(). Bresenham’s Line Algorithm perhaps?
 
-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.
+News: Channel NewsAsia RSS. MCU parses XML directly. Character glyphs stored as
+bitmaps in sprites directory.
 
-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:
+Weather: DHT22 via PWM. 26µs/50µs/70µs pulses too fast for standard ESP32 APIs.
+Compare relative pulse widths:
 
 ```
 static inline int dht_await_pin_state(int state, int timeout)
@@ -51,12 +44,12 @@ static inline int dht_await_pin_state(int state, int timeout)
     for (t = 0; t < timeout; t += delta) {
         ets_delay_us(delta);
         if (gpio_get_level(DHT_PIN) == state)
-          return t;
+            return t;
     }
     return 0;
 }
 
-static inline int dht_get_raw_data(unsigned char buf[DHT_DATA_LEN])
+static inline int dht_get_raw_data(unsigned char buf[BUFLEN])
 {
     int rc;
     unsigned char i, pwl, pwh;
@@ -81,7 +74,7 @@ static inline int dht_get_raw_data(unsigned char buf[DHT_DATA_LEN])
         return 0;
     }
 
-    for (i = 0; i < DHT_DATA_LEN; i++) {
+    for (i = 0; i < BUFLEN; i++) {
         if (!(pwl = dht_await_pin_state(1, 50))) {
             rc = 4;
             xQueueSend(dht_evt_queue, &rc, (TickType_t) 0);
@@ -98,18 +91,15 @@ static inline int dht_get_raw_data(unsigned char buf[DHT_DATA_LEN])
 }
 ```
 
-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.
+Ported from <a href="https://github.com/Fonger/ESP8266-RTOS-DHT"
+class="external" target="_blank" rel="noopener noreferrer">ESP8266</a>.
 
-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.
+After flashing new versions, display would stop responding. Didn't observe this
+with e-reader. Issue occurs spontaneously. Couldn't find root cause. Making a
+change like adding a comment or tweaking delay in refresh() (then changing
+back) fixed it. Noisy electrical connections?
 
-Etlas has been running reliably for over a year since August 2024.
+Once running, it runs: August 2024 - December 2025.
 
-Files: [source.tar.gz](source.tar.gz)
+Commit:
+[a92c86a](https://git.asciimx.com/etlas/commit/?id=a92c86ac1592c2137d3d1fec1668eacc2d0ca581)