In two days the E-Display went from a bare controller board to a 4.26″ e-paper panel painting ink landscapes that drift slowly across the screen. Generative art is now the project; the weather screen stays possible but comes second.
01 Board alone · 2026-10-01
The first step left the screen in its box. The controller board (Adafruit Feather ESP32-S3, 8 MB) went on a USB-C data cable to the Mac, the 1500 mAh battery on its switch cable, and a test program onto the board. If the screen later stayed blank, these would already be ruled out.
| Test | Result |
|---|---|
| Mac sees the board | Pass |
| Compile and flash | Pass |
| Fuel gauge answers | Pass |
| LED blinks | Pass |
| Battery 4.00 V, steady | Pass |
| Runs on battery alone | Pass |
| Joins Wi-Fi, controlled from a phone | Pass |
| Battery life with Wi-Fi on | Pending |
Five lessons from that day:
- No battery still reads a voltage. With nothing plugged in, the gauge showed 4.1 V, falling, at 101.9 %. A real cell holds steady.
- The gauge needs minutes to learn. It said 99.9 % at 4.00 V; the truth was about 80 to 85 %.
- Charge-only USB cables power the board, but no port appears.
- On USB the battery charges. Unplug for any battery test.
- Deep sleep hides the USB port. Hold BOOT, tap RESET, then upload.
02 First screen · 2026-10-02
Two header strips soldered onto the board, nine wires plugged on, and the panel drew. Two details decided whether it showed anything at all: the screen's power pin must be driven high by the firmware, and this panel wants a short reset pulse.
| Measured | Value | Unit |
|---|---|---|
| Full refresh, whole panel | 2.4 to 2.8 | s |
| Partial refresh | 0.42 | s |
| Partial refresh, larger window | 0.87 | s |
03 Paintings that move
A landscape is drawn as one long strip, 1800 × 480 pixels and 108 KB. The board downloads it once and slides an 800-pixel window along it, a few pixels at a time, with partial refreshes. Sending each window straight to the display controller, instead of through the graphics library's paging, cut one frame from 1515 ms to 877 ms.
The Mac draws the art and serves the settings. The board reads them with every painting it downloads, so scroll speed, step size and refresh rhythm change from a control page with no reflash. When new firmware is needed, it goes on by drag and drop: double-tap RESET, the board appears as a drive, copy one file.
Seven styles run today: Shan Shui landscapes, a landscape inscribed with a Song ci poem, birds, fish, flowers, vertical poems and calligraphy strokes. They are open-source generators, most of them by Lingdong Huang, whose work is ink, line and Chinese text: exactly what a 1-bit e-paper panel does well. All seven are on the lab page.
04 Next
- A battery test is running, the frame painting and drifting on battery alone. Results go in the next log.
- Print the case and fit everything.
- Move the styles that are pure maths, the birds, fish and strokes, onto the board itself, so the frame can paint without the Mac.