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diff --git a/_site/log/e-reader/index.html b/_site/log/e-reader/index.html deleted file mode 100644 index 13b4efa..0000000 --- a/_site/log/e-reader/index.html +++ /dev/null @@ -1,117 +0,0 @@ -<!DOCTYPE html> -<html> - <head> - <meta charset="utf-8"> - <meta name="viewport" content="width=device-width, initial-scale=1"> - <title>512KB e-reader</title> - <link rel="stylesheet" href="/assets/css/main.css"> - <link rel="stylesheet" href="/assets/css/skeleton.css"> -</head> - - - <body> - - <div id="nav-container" class="container"> - <ul id="navlist" class="left"> - - <li > - <a href="/" class="link-decor-none">hme</a> - </li> - <li > - <a href="/projects/" class="link-decor-none">poc</a> - </li> - <li > - <a href="/about/" class="link-decor-none">abt</a> - </li> - <li> - <a href="/cgi-bin/find.cgi" class="link-decor-none">lup</a> - </li> - <li> - <a href="/feed.xml" class="link-decor-none">rss</a> - </li> - </ul> -</div> - - - - <main> - <div class="container"> - <div class="container-2"> - <h2 class="center" id="title">512KB E-READER</h2> - <h5 class="center">24 OCTOBER 2023</h5> - <br> - <div class="twocol justify"><p>First project with e-paper.</p> - -<video style="max-width:100%;" controls="" poster="poster.png"> - <source src="ereader.mp4" type="video/mp4" /> -</video> - -<p>ESP-WROOM-32, 7.5” Waveshare e-paper display, three-button interface -(prev/next/sleep).</p> - -<p>Memory: 512KB SRAM + 4MB flash. Internal flash unsuitable for storing books due -to P/E cycle limit. Used HTTP Range requests to stream them on-demand. -Progress saved to RTC memory to survive deep sleep without flash wear.</p> - -<p>PDFs are rasterized and stored as sequences of bitmaps on a server. 1 byte = 8 -pixels, 1 page = 48KB (display resolution), headerless. Optimized for Range -requests without server-side logic:</p> - -<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>int r0 = ((page_n - 1) * PAGE_SIZE); -int rn = page_n * PAGE_SIZE - 1; - -int n = snprintf(NULL, 0, "bytes=%d-%d", r0, rn) + 1; -char *buf = malloc(sizeof(char) * n); -snprintf(buf, n, "bytes=%d-%d", r0, rn); - -esp_http_client_set_header(http_client, "Range", buf); -esp_http_client_perform(http_client); -</code></pre></div></div> - -<p>Three pages (prev/current/next) held in a buffer—maximum possible. Upon -request, embedded software cycles the buffer, updates the screen, prefetches -the next page.</p> - -<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>c_page_num++; -pg.page_num = c_page_num + 2; -pg.page_buf = pages[(c_page_num + 1) % PAGE_LEN]; - -xSemaphoreGive(mutex); -xQueueSend(http_evt_queue, &pg, portMAX_DELAY); - -epd_draw_async(pages[c_page_num % PAGE_LEN], PAGE_SIZE); -epd_draw_await(); -</code></pre></div></div> - -<p>System isn’t as responsive as I’d hoped. Scheduling GPIO, SPI, and HTTP tasks -on a single thread causes input lag. Pinned GPIO/SPI tasks to one core and the -HTTP task to the other.</p> - -<p>Better, but screen updates block user input.</p> - -<p>Moved the SPI buffers to DMA and made the transfers async. Few more cycles -saved.</p> - -<p>Can’t think of anything else.</p> - -<p>Verdict: Functional but limited. Led to <a href="../etlas/">Etlas</a>.</p> - -<p>Commit: -<a href="https://git.asciimx.com/esp32-e-reader/commit/?id=7f691c46093933b67aab466c0ca582ace8ab73d4">7f691c4</a></p> -</div> - <p class="post-author right">by W. D. Sadeep Madurange</p> - </div> - </div> - </main> - - <div class="footer"> - <div class="container"> - <div class="twelve columns right container-2"> - <p id="footer-text">© ASCIIMX - 2026</p> - </div> - </div> -</div> - - - </body> -</html> |