SageSlate E-Ink Hardware Guide¶
SageSlate turns cheap e-ink panels and an ESP32 into wireless player handout screens for your TTRPG sessions. Each screen connects to your WiFi network and receives images pushed from the ScreenSage app over a TCP connection — no Bluetooth, no pairing, no fuss.
Parts List (per screen)¶
| Part | Notes |
|---|---|
| Waveshare 4.2" e-ink display + driver board | 400×300, black/white |
| ESP32 development board (e.g. ESP32-WROOM-32) | Any standard 38-pin board works |
| 3.7 V LiPo battery (LP402535 or similar) | Shown in build photo |
| TP4056 USB-C charging module | Optional — lets you charge without opening the case |
| Toggle switch | For power on/off |
| Jumper/dupont wires | For wiring ESP32 to driver board |
| 3D printed case | STL files provided (see below) |
3D Printing the Case¶
Four STL files are in SageSlate/stls/:
| File | Part |
|---|---|
case_4_2_v5.stl |
Main body |
case_4_2_v5_stand.stl |
Desk stand (print ×2) |
lid.stl |
Back cover |
Print in PLA or PETG. The body holds the e-ink panel face-down, the ESP32, and the battery. The two triangular stands clip on the sides so the screen can sit at an angle on a table.
Wiring¶
Connect the Waveshare e-ink driver board to the ESP32 using the SPI pins defined in SageSlate/ESP32_wifi_code/epd.h:
| ESP32 GPIO | Driver board pin |
|---|---|
| 13 | SCK (CLK) |
| 14 | DIN (MOSI) |
| 15 | CS |
| 25 | BUSY |
| 26 | RST |
| 27 | DC |
| 3.3 V | VCC |
| GND | GND |
The battery connects via the TP4056 module so it can be charged over USB-C. Wire a toggle switch in series on the positive line for a physical power switch.
Flashing the ESP32¶
1. Install Arduino IDE¶
Download from arduino.cc. Install the ESP32 board package:
- Open File → Preferences
- Add to Additional Boards Manager URLs:
- Open Tools → Board → Boards Manager, search esp32, install esp32 by Espressif Systems.
2. Configure WiFi credentials¶
Open SageSlate/ESP32_wifi_code/srvr.h and update these three lines near the top:
const char *ssid = "your_wifi_name";
const char *password = "your_wifi_password";
const char* hostname = "einkScreen0"; // unique name per display
Give each screen a different hostname (einkScreen0, einkScreen1, etc.) so you can tell them apart on your network.
3. Set a static IP address¶
Still in srvr.h, set a static IP that doesn't conflict with other devices:
IPAddress staticIP(192, 168, 1, 200); // change to suit your network
IPAddress gateway(192, 168, 1, 1);
IPAddress subnet(255, 255, 255, 0);
IPAddress dns(8, 8, 8, 8);
Use a different last octet for each screen (e.g. .200, .201, .202).
4. Set the display type¶
In SageSlate/ESP32_wifi_code/Loader_esp32wf.ino, the display type is set in setup():
Supported indices:
| Index | Display | Resolution |
|---|---|---|
| 0 | 1.54 inch | 200×200 |
| 3 | 2.13 inch | 250×122 |
| 7 | 2.7 inch | 264×176 |
| 9 | 2.9 inch | 296×128 |
| 44 | 4.2 inch | 400×300 |
| 19 | 7.5 inch | 800×480 |
5. Upload¶
- Select Tools → Board → ESP32 Dev Module
- Select the correct Port
- Click Upload
Watch the Serial Monitor (115200 baud) — on boot you should see:
Sending Images Over WiFi¶
With the ESP32 running, use the provided Python script to push any image to the screen.
Install dependencies¶
Send an image¶
Example:
The script will: 1. Open and resize the image to the display's resolution (default 400×300 for 4.2") 2. Convert it to 1-bit black and white 3. Pack the pixels into bytes and send them over TCP port 8080 4. The ESP32 receives the data and refreshes the e-ink panel
Optional flags:
| Flag | Default | Description |
|---|---|---|
--port |
8080 | TCP port |
--width |
400 | Target image width in pixels |
--height |
300 | Target image height in pixels |
Match --width and --height to your display's resolution (see table above).
Finished Build¶
The completed screen sits on its printed triangle stands. E-ink holds the last image indefinitely with zero power draw — the battery only matters while the image is being updated.
Troubleshooting¶
Screen doesn't connect to WiFi
- Double-check SSID/password in srvr.h and re-flash.
- Check that your router's 2.4 GHz band is enabled — ESP32 does not support 5 GHz.
Python script errors "Connection refused"
- Confirm the static IP in srvr.h matches the address you're sending to.
- Check the Serial Monitor to verify the ESP32 printed its IP on boot.
Image looks wrong (inverted or garbled)
- Make sure --width and --height match your actual display resolution.
- The 2.7" display (index 7) automatically inverts its bits — this is handled in firmware.
Screen doesn't refresh - E-ink can take 2–3 seconds to fully refresh. Wait before assuming it failed. - If using a 3-colour display, the red channel is sent as all-white by default — only black and white content will appear.