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| author | Sadeep Madurange <sadeep@asciimx.com> | 2026-01-05 12:17:09 +0800 |
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| committer | Sadeep Madurange <sadeep@asciimx.com> | 2026-01-05 12:17:09 +0800 |
| commit | 577aa865c2f53a46a5869b1e4dda69dc06d0a962 (patch) | |
| tree | 91bbb8e8e9cc39ac5a75f05395e9ae1b0fe54b76 /_site/log | |
| parent | 75aa500d7644f15f4a45fe2f64de1c526b87cf95 (diff) | |
| download | www-577aa865c2f53a46a5869b1e4dda69dc06d0a962.tar.gz | |
Tighten e-reader prose.
Diffstat (limited to '_site/log')
| -rw-r--r-- | _site/log/e-reader/index.html | 72 |
1 files changed, 31 insertions, 41 deletions
diff --git a/_site/log/e-reader/index.html b/_site/log/e-reader/index.html index a5dbc01..41f58ff 100644 --- a/_site/log/e-reader/index.html +++ b/_site/log/e-reader/index.html @@ -3,7 +3,7 @@ <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> - <title>ESP32 e-reader prototype</title> + <title>ESP32 prototype e-reader</title> <link rel="stylesheet" href="/assets/css/main.css"> <link rel="stylesheet" href="/assets/css/skeleton.css"> </head> @@ -37,7 +37,7 @@ <main> <div class="container"> <div class="container-2"> - <h2 class="center" id="title">ESP32 E-READER PROTOTYPE</h2> + <h2 class="center" id="title">ESP32 PROTOTYPE E-READER</h2> <h5 class="center">24 OCTOBER 2023</h5> <br> <div class="twocol justify"><p>First project with e-paper displays and ESP32.</p> @@ -46,61 +46,51 @@ <source src="ereader.mp4" type="video/mp4" /> </video> -<p>System: ESP-WROOM-32, 7.5” Waveshare e-paper display, three buttons +<p>ESP-WROOM-32, 7.5” Waveshare e-paper display, three-button interface (prev/next/sleep).</p> -<p>2023-09-23: 512KB SRAM, 4MB flash (shared with FreeRTOS and ESP-IDF). Not -enough storage for books. Using ESP32’s built-in WiFi to stream them over HTTP. -Recording the reading progress in RTC memory.</p> +<p>Memory: 512KB SRAM + 4MB flash–insufficient for local library. Streams via +HTTP Range requests over WiFi. Reading progress saved to RTC memory; persists +through deep sleep.</p> -<p>Rasterized pages encoded as tightly packed bitmaps (1 byte => 8 pixels), no -headers, arranged along 48 KB (480x800) boundaries; Reader can stream pages -using HTTP Range requests with zero server-side logic. Keeps both ends lean.</p> +<p>EBM format: Raw bitmap sequence. 1 byte = 8 pixels, 1 page = 48 KB (display +resolution), headerless. Optimized for HTTP Range requests:</p> -<p>Page table stores 3 pages (prev/current/next) in a circular buffer. When the -user requests a page, program cycles through the table, updates the screen, and -downloads the next page.</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; -<p>Responsiveness is inadequate. Scheduling GPIO (user input), SPI, and HTTP on -one core causes input lag. Pinned the GPIO and SPI tasks to one core, the HTTP -task to the other core.</p> +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); -<p>Better, but screen updates are blocking user input; Made SPI transfer async:</p> - -<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>void epd_draw_async(const uint8_t *buf, size_t n) -{ - static spi_transaction_t t[3]; +esp_http_client_set_header(http_client, "Range", buf); +esp_http_client_perform(http_client); +</code></pre></div></div> - memset(&t[0], 0, sizeof(t[0])); - t[0].length = 8; - t[0].tx_data[0] = 0x13; - t[0].user = (void*) 0; - t[0].flags = SPI_TRANS_USE_TXDATA; +<p>Page buffer: Three pages (prev/current/next) in RAM—maximum possible. On +request: cycles buffer, updates screen, prefetches next page.</p> - memset(&t[1], 0, sizeof(t[1])); - t[1].length = 8 * n; - t[1].tx_buffer = buf; - t[1].user = (void*) 1; +<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]; - memset(&t[2], 0, sizeof(t[2])); - t[2].length = 8; - t[2].tx_data[0] = 0x12; - t[2].user = (void*) 0; - t[2].flags = SPI_TRANS_USE_TXDATA; +xSemaphoreGive(mutex); +xQueueSend(http_evt_queue, &pg, portMAX_DELAY); - for (int i = 0; i < 3; i++) - spi_device_queue_trans(spi, &t[i], portMAX_DELAY); -} +epd_draw_async(pages[c_page_num % PAGE_LEN], PAGE_SIZE); +epd_draw_await(); </code></pre></div></div> -<p>Much better.</p> +<p>Responsiveness: inadequate. 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>2023-10-06: Moved the page table to DMA-capable memory; Reclaimed a few more -CPU cycles from the SPI transfers.</p> +<p>Better, but screen updates block user input. Moved SPI buffers to DMA and made +transfers async. Few more cycles saved.</p> <p>Can’t think of anything else.</p> -<p>Verdict: Works but limited. Led to <a href="../etlas/">Etlas</a>.</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> |