Smart E-Paper Display Module

01Specs

Display

Waveshare 4.2" e-paper, 400 × 300, 1-bit black and white

Controller

ESP32 on a custom KiCad PCB, hand assembled

Power

3.7 V 1000 mAh Li-ion, TP4056 USB-C charging, on-board boost converter

Storage

microSD slideshow, 400 × 300 raw .bin images

Enclosure

SolidWorks, 3D printed, 3-part press fit, about 108 × 114 × 58 mm

02Design iterations

v1

Rack and stand

A rack and stand to hold the display.

v2

Two-piece enclosure

Housing and front plate.

v3

Three-piece press fit

Added a backplate with USB-C and microSD slots, so the frame charges and takes a new card without opening.

SolidWorks: v3 parts

housing

backplate with USB-C and microSD slots

03Electronics

• ESP32 on a custom PCB designed in KiCad and hand assembled
• 3.7 V 1000 mAh Li-ion pack, TP4056 USB-C charging module and a boost converter on the board

KiCad schematic

KiCad PCB layout render

Bare PCB before assembly

KiCad 3D viewer render of the PCB

Assembled PCB, top view

04Firmware

• Slideshow from microSD: 400 × 300 raw .bin images, one pushbutton to advance
• Deep sleep between image changes
• Wi-Fi upload page for loading photos, with crop, portrait and rotate options

05Testing and problems solved

• Display stopped refreshing: tracked it down to loose connections
• Replaced a failed charger module and lowered the charge current
• Debugged serial output: the cause was a baud rate mismatch
• Added pocket cutouts in the enclosure for the display wiring

Bench test of the board with the housing

Board mounted in the housing

06Results

• Working frame: microSD slideshow, pushbutton control and Wi-Fi photo upload
• Charge current set to about 500 mA; a full charge takes about 2 hours
• Standby: 10 to 14 days (estimate)
• Three-part press-fit enclosure, about 108 × 114 × 58 mm

07What I would change in v2

• Run the ESP32 from a proper regulated rail instead of directly from the battery
• Add reverse polarity protection
• Add a battery switch