Build a LibrePad at home.

Gather the parts

Everything comes off the shelf. The two boards come from Seeed Studio and the screen from Good Display; the rest is in any electronics parts drawer.

Load the firmware onto the XIAO

Do this first, on the bare board. It is the easiest moment to find out the XIAO works, before anything is soldered to it.

1. Install the Arduino IDE.
2. In File → Preferences, add this to Additional boards manager URLs:
   https://files.seeedstudio.com/arduino/package_seeeduino_boards_index.json
3. In the Boards Manager, install Seeed nRF52 Boards (LibrePad is built with version 1.1.13), then choose the board Seeed XIAO nRF52840: not the "Sense", and not the "mbed-enabled" package. The libraries the firmware needs come with it; don't install other versions of them.
4. Get the firmware: the firmware/librepad folder of the LibrePad source (on GitHub soon, see Open source). Open librepad.ino.
5. Plug the XIAO in with a USB-C cable that carries data, choose its port, and press Upload.
6. Open the Serial Monitor at 115200 baud. The reader reports what it finds every few seconds. Until the memory is added in step 4, it says it can't find it; that's expected.

Connect the screen

The breakout board sits between the XIAO and the screen: the XIAO plugs into it, and the screen's ribbon cable plugs into its connector.

1. Open the latch on the breakout's screen connector, slide the panel's ribbon all the way in, and close the latch.
2. Fit the XIAO onto the breakout, matching the printed pin names.
3. With the multimeter, check that the breakout's BUSY pin connects to the XIAO's D2. On our board it didn't, so we soldered a short wire from BUSY to D2.

Add the memory

The book lives on the W25Q128 module, 16 MB, enough for a long novel with its quiz. It shares the screen's clock and data pins and gets two of its own.

Check it with the Serial Monitor. A blank memory with no book yet looks like this:

boot: LIBREPAD image INVALID, parse_reason=2, store_ok=1
      waiting for an update over USB or BLE

store_ok=1 means the memory answered; parse_reason=2 means it's empty, which it should be. If you see store_ok=0, check the six wires.

Wire the four buttons

Two pins read all four buttons. On each pin, one button connects straight to 3.3 V and the other through a 3 kΩ resistor, so the pin sees a different voltage for each; a 10 kΩ resistor holds it at zero when nothing is pressed.

Add the refresh switch

One side of the switch to D9, the other to GND. That's all: the firmware supplies the pull-up.

Flip it either way and the reader redraws the page from clean. E-paper can keep a faint trace of the page before; this clears it.

Add the battery

The breakout board has a booster that turns the battery's 3.7 V into 5 V for the XIAO, and a switch that turns the whole reader on and off.

• LiPo battery3.7 V, protected
• →
• Charging modulecharges and protects
• →
• Breakout: BATthe pads underneath
• →
• Breakout: switchon and off
• →
• Boosterabout 4.8 V out
• →
• XIAO: 5Vit makes its own 3.3 V

1. Solder the charging module's output to the breakout's BAT pads, on the underside of the board.
2. If the XIAO is wired to the breakout rather than plugged into it, add one wire from the breakout's 5V to the XIAO's 5V.
3. Switch on and measure: about 4.8 V on 5V, and 3.3 V on 3V3.

Build the case

The case is 3D-printed. Its models will be on Onshape, ready to print as they are or to change (see Open source).

1. Print the parts.
2. Fit the screen behind the front window, then the boards and the battery behind it.
3. Mount the four buttons in a row, in their order from step 5, and put the switch where a grown-up can reach it.
4. Before closing it up, turn a few pages. If the page is upside down, the firmware can turn it (LP_DISPLAY_ROTATE_180 in board_pins.h); never repack the books.
5. Close it with the back cover.

Send it a book

Books go onto the reader over Bluetooth, from the LibrePad Library, a web app that runs in Chrome on an Android phone or a computer. (An iPhone can browse the Library but can't send: its browsers don't have Web Bluetooth.)

1. Open librepad.app in Chrome and sign in.
2. In Books, pick a book. Leave Quiz after each chapter on, or turn it off.
3. Press Send to reader and choose LibrePad Reader in Chrome's list. Keep the phone close until it says it's done.
4. The reader opens the book by itself, on its first page.

Read

That's it: hand it over. Here is what each button does on each screen, so you can test yours. To see the screens as a child does, try the buttons on the home page.

• A few quick taps on a chapter button skip that many chapters.
• A page turns in about two seconds. Every sixth turn, the screen flashes once to keep the page crisp.
• Taking a quiz again is practice: the score stays the first try's, and only the Library can reset it.
• The reader remembers where it was in each of the last twelve books sent to it, quiz answers included.