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T-Display S3 Pro RSVP Reader

An offline-first RSVP reader for the LilyGO T-Display S3 Pro. It renders one white word on a black, landscape display and never starts Wi-Fi or Bluetooth.

What you need

A LilyGO T-Display S3 Pro and a USB-C data cable. A charge-only cable cannot upload firmware.
A computer with internet access for the first build, Python 3, and a terminal.
A microSD card formatted as FAT32. The reader uses this as its book library.
This repository, cloned or downloaded to your computer.

The first build downloads the ESP32 toolchain and display library. The reader does not need network access after it has been flashed.

1. Install PlatformIO Core

PlatformIO Core is the command-line build and upload tool used by this project. Install it in your normal user account; do not use sudo.

macOS or Linux

Confirm Python 3 is available:

python3 --version

Then use PlatformIO's installer:

curl -fsSL -o get-platformio.py https://raw.githubusercontent.com/platformio/platformio-core-installer/master/get-platformio.py
python3 get-platformio.py

The installer puts pio at ~/.platformio/penv/bin/pio. Add that directory to your shell PATH, or use the full path in every command below. For the current shell only:

export PATH="$HOME/.platformio/penv/bin:$PATH"
pio --version

On Linux, if the serial device appears but uploads fail with a permission error, add your user to the serial-device group and then sign out and back in:

sudo usermod -a -G dialout "$USER"

Windows

Install Python 3, then follow PlatformIO's official installer instructions. After installation, open a new PowerShell window and confirm:

pio --version

PlatformIO's installer documentation is the authoritative reference for all operating systems: https://docs.platformio.org/en/latest/core/installation/methods/installer-script.html.

2. Prepare a book card

Format the microSD card as FAT32.
Create a directory named books at the card's root.
Create one folder per book inside books. Each book folder needs a TOC.txt, UTF-8 text files for its sections, and matching .rsvp sidecars generated by the converter.

TOC.txt controls both section order and title-card text. Each non-empty line names a section and its file is that name plus .txt.

The resulting card must look like this:

microSD root/
└── books/
    └── Example Book/
        ├── TOC.txt
        ├── Dedication.txt
        ├── Dedication.rsvp
        ├── Chapter 1.txt
        ├── Chapter 1.rsvp
        ├── Chapter 2.txt
        └── Chapter 2.rsvp

For the example above, TOC.txt contains:

Dedication
Chapter 1
Chapter 2

Generate this layout from an EPUB with the included converter:

python3 -m pip install -r requirements.txt
python3 epub_to_chapters.py book.epub "Example Book"

Copy the resulting Example Book directory into /books on the card. A section may be up to 1.5 MiB. The converter writes CONVERSION_REPORT.txt in the book directory. It records any unsupported non-ASCII characters left after normalizing common punctuation, ligatures, accents, whitespace, fractions, and ornamental breaks. Review that report before copying the book: transliterate or replace reported characters deliberately, or defer the book until a Unicode-capable font is available. The included display font is best for printable ASCII.

The converter also writes a compact <section>.rsvp file alongside every section. Its versioned records preserve italic and bold EPUB markup—including semantic tags, CSS classes, and inline CSS—using delta-encoded word indexes, and include a reserved timing-modifier field for a future reading-timing pass. The reader validates the sidecar's fingerprint against its .txt file and safely ignores it if it is missing, stale, or malformed. Valid italic and bold records select matching reader-font variants.

Eject the card safely and insert it in the board before powering the board.

3. Build the firmware

Open a terminal in this project directory:

cd /path/to/tds3p-rsvp-reader
pio run

On the first run, PlatformIO downloads the pinned ESP32 platform, compiler, and TFT_eSPI dependency. A successful build ends with SUCCESS and creates the firmware under .pio/build/rsvp_reader/.

The project targets the T-Display S3 Pro's 16 MB flash and 8 MB OPI PSRAM. It defaults to the v1.1 16-step backlight driver. If your board is the original v1.0 hardware, add this line under build_flags in platformio.ini before building:

  -DTDS3P_V1_0

4. Connect and identify the board

Connect the board directly to the computer with the USB-C data cable.
Give the operating system a few seconds to enumerate it.
List serial ports:

pio device list

Typical ports are /dev/ttyACM0 or /dev/ttyUSB0 on Linux, /dev/cu.usbmodem* on macOS, and COM3 on Windows. Note the port belonging to the board.

5. Upload and start the reader

Let PlatformIO select the port automatically:

pio run -t upload

If it selects the wrong port or does not find one, supply it explicitly:

pio run -t upload --upload-port /dev/ttyACM0

Replace /dev/ttyACM0 with the port from the previous step. On Windows, for example, use --upload-port COM3.

After a successful upload, the display shows the current section title and is paused. If it shows NO BOOKS, check that the card is inserted, FAT32, and contains at least one /books/<book>/TOC.txt with a listed section file.

If the board is not detected or an upload repeatedly fails, force download mode:

Hold BOOT (the lower-left button, GPIO0).
While holding BOOT, press and release RESET (upper-left).
Release BOOT.
Run the upload command again.

6. Read

Control	Reading view	Menu or picker
BOOT / GPIO0	Open menu	Close/cancel without saving
Touch edge Home button	Play or pause	Open highlighted option / apply
Upper-right / GPIO12	Previous paragraph or section	Move selection backward
Lower-right / GPIO16	Next paragraph or section	Move selection forward

Do not hold BOOT while pressing RESET during normal use; that combination is the manual download mode used for recovery above.

The default is 300 WPM. While paused, the backlight dims after 20 seconds, switches off after one minute, and the ESP32 deep-sleeps after ten minutes. GPIO12 wakes it.

Resume and power behavior

The reader saves the selected section, WPM, brightness, and font settings in the ESP32's nonvolatile storage. On the next boot or wake it opens the same section's title card and remains paused; pressing the touch-edge Home button begins at that section's first word. It defers full chapter-list validation until chapter browsing is needed, so normal startup opens only the selected chapter and its sidecar.

The physical power switch only disconnects the battery. USB power is sufficient for development and flashing. The reader intentionally has no Wi-Fi, Bluetooth, cloud account, or synchronization feature.

Troubleshooting

No serial port: use another USB-C cable; many included cables only charge.
Upload cannot connect: use the BOOT + RESET sequence in step 5, then retry.
Permission denied on Linux: complete the dialout group step and log out and back in.
NO BOOKS: reformat the card FAT32, create /books/<book>, and add a TOC.txt plus the listed .txt section files. Confirm the card is fully seated. Dot-prefixed folders such as .Trash are ignored.
Black display after boot: press GPIO12 to wake it if it has slept; otherwise reflash and check whether the v1.0 backlight build flag is needed.
Build fails before compilation: rerun pio run with internet access so PlatformIO can download the required packages.

Limits of the first MVP

It reads sections up to 1.5 MiB from /books/<book>/<section>.txt, in the order declared by that book's TOC.txt.
The built-in display font is best for printable ASCII text. UTF-8 text files are accepted, but accented/non-Latin characters need a Unicode font addition before they will render correctly.
The v1.1 backlight driver is the default. Define TDS3P_V1_0 in build_flags for an original v1.0 board.

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