512KB e-reader

From a851a2d646f439f7126c232ba1524c55a8990872 Mon Sep 17 00:00:00 2001 From: Sadeep Madurange Date: Fri, 9 Jan 2026 16:45:56 +0800 Subject: Remove _site from git. --- _site/log/e-reader/circuit.svg | 145 --------------------------------------- _site/log/e-reader/ereader.mp4 | Bin 3101166 -> 0 bytes _site/log/e-reader/index.html | 117 ------------------------------- _site/log/e-reader/poster.png | Bin 674187 -> 0 bytes _site/log/e-reader/source.tar.gz | Bin 14304 -> 0 bytes _site/log/e-reader/thumb_sm.png | Bin 240117 -> 0 bytes 6 files changed, 262 deletions(-) delete mode 100644 _site/log/e-reader/circuit.svg delete mode 100644 _site/log/e-reader/ereader.mp4 delete mode 100644 _site/log/e-reader/index.html delete mode 100644 _site/log/e-reader/poster.png delete mode 100644 _site/log/e-reader/source.tar.gz delete mode 100644 _site/log/e-reader/thumb_sm.png (limited to '_site/log/e-reader') diff --git a/_site/log/e-reader/circuit.svg b/_site/log/e-reader/circuit.svg deleted file mode 100644 index fd7508b..0000000 --- a/_site/log/e-reader/circuit.svg +++ /dev/null @@ -1,145 +0,0 @@ - - - - \ No newline at end of file diff --git a/_site/log/e-reader/ereader.mp4 b/_site/log/e-reader/ereader.mp4 deleted file mode 100644 index 89e05eb..0000000 Binary files a/_site/log/e-reader/ereader.mp4 and /dev/null differ 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 @@ - - - - - - 512KB e-reader - - - - - - - -

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- hme -
- poc -
- abt -
- lup -
- rss -

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512KB E-READER

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24 OCTOBER 2023

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First project with e-paper.

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ESP-WROOM-32, 7.5” Waveshare e-paper display, three-button interface -(prev/next/sleep).

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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.

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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:

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int r0 = ((page_n - 1) * PAGE_SIZE);
-int rn = page_n * PAGE_SIZE - 1;
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-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);
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-esp_http_client_set_header(http_client, "Range", buf);
-esp_http_client_perform(http_client);
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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.

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c_page_num++;
-pg.page_num = c_page_num + 2;
-pg.page_buf = pages[(c_page_num + 1) % PAGE_LEN];
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-xSemaphoreGive(mutex);
-xQueueSend(http_evt_queue, &pg, portMAX_DELAY);
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-epd_draw_async(pages[c_page_num % PAGE_LEN], PAGE_SIZE);
-epd_draw_await();
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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.

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Better, but screen updates block user input.

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Moved the SPI buffers to DMA and made the transfers async. Few more cycles -saved.

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Can’t think of anything else.

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Verdict: Functional but limited. Led to Etlas.

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Commit: -7f691c4

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by W. D. Sadeep Madurange

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- - - - - - diff --git a/_site/log/e-reader/poster.png b/_site/log/e-reader/poster.png deleted file mode 100644 index 1e222d2..0000000 Binary files a/_site/log/e-reader/poster.png and /dev/null differ diff --git a/_site/log/e-reader/source.tar.gz b/_site/log/e-reader/source.tar.gz deleted file mode 100644 index 3e343a7..0000000 Binary files a/_site/log/e-reader/source.tar.gz and /dev/null differ diff --git a/_site/log/e-reader/thumb_sm.png b/_site/log/e-reader/thumb_sm.png deleted file mode 100644 index 7c971e8..0000000 Binary files a/_site/log/e-reader/thumb_sm.png and /dev/null differ -- cgit v1.2.3