Display Mode

Display Mode

Display Mode lets a compatible tool send custom images to Rand/0's e-ink display over the same local network. The display is 200 × 200 pixels and supports black-and-white and four-level grayscale images.

Before You Begin

Make sure that:

1. You have connected Rand/0 to Wi-Fi once using Wi-Fi, so it remembers an available network.
2. The battery is sufficiently charged, or the device is connected to power. Display Mode will not start when the battery is too low.
3. The phone or computer sending the image is connected to the same local network as Rand/0.
4. You have a tool that supports Rand/0 Display Mode.

Enter Display Mode

By default, you can enter from this location:

• Main menu → More → Display → Confirm.

If you have customized the home screen, open Display wherever you placed it.

Rand/0 restarts and automatically connects to a remembered Wi-Fi network. When the connection succeeds, the device IP address appears in the center of the display.

The ready screen also shows a QR code that opens this Display Mode guide. Scan it if you need the connection or protocol details.

Connect and Send an Image

1. Open a tool that supports Rand/0 Display Mode.
2. Enter the IP address shown on the device and start the connection.
3. Follow the tool's instructions to select an image and send it to Rand/0.

Only one tool can be connected at a time. When a new connection is established, the previous connection is disconnected automatically.

Button Controls

E-ink displays refresh slowly and are better suited to static images. When images are sent continuously, Rand/0 keeps only the latest image; intermediate images may not appear.

After you exit Display Mode, Rand/0 returns to normal mode. If the device resets unexpectedly, it will not enter Display Mode again automatically.

Compatible Tool Protocol

Display Mode exposes these WebSocket endpoints on the device's local IP address:

Send one binary frame for each image. Pixels are row-major from left to right and top to bottom, with the highest bits representing the leftmost pixels. In black-and-white mode, 1 is white and 0 is black. In four-gray mode, 00 is white, 01 is light gray, 10 is dark gray, and 11 is black.

Only one client is active at a time. A new connection replaces the previous one. If images arrive faster than the display can refresh, Rand/0 keeps only the latest frame.

The device sends button events and errors as text JSON. For example:

{"type":"key","key":"up","action":"short"}

Invalid frame types or lengths return an error such as expected_binary_5000 or expected_binary_10000.

Common Prompts