E-Ink Etch-A-Sketch

A handheld E-Ink drawing toy — turn the knobs to draw, shake to erase — built around an ultra-low-power STM32 so it can run for days on a single coin cell.

Problem

E-Ink only draws power when the image changes, which makes it perfect for a battery device that's mostly idle. The challenge is everything around it: a clean low-power PCB, a custom controller driver, and an enclosure that all fits a coin cell's tiny power budget.

Approach

• PCB. A low-power STM32L433 board in KiCad with coin-cell power management using eFuses and charge pumps, an I2C accelerometer for shake-to-erase, and ADC-read potentiometers for the drawing controls.
• Firmware. A custom driver for the IT8951 E-Ink controller over SPI to handle display bring-up and updates, written in embedded C.
• Mechanical. A compact 3D-printed enclosure in SolidWorks accounting for mounting features, pin headers, and test points for integration.

Result

• Power architecture targeting roughly 60 hours of operation on a single coin cell.
• Working IT8951 SPI driver bringing up and updating the E-Ink panel.
• PCB in fabrication with the enclosure designed around it for assembly.

What's next: finish board bring-up, validate the real-world battery life, and refine the enclosure for a cleaner hand feel.