Home Assistant E-Ink Dashboard

A simple, battery-powered, Waveshare 2.9" e-ink display for Home Assistant, powered by ESPHome & ESP32.

Project Overview

This project is a low-power, always-ready e-ink display for Home Assistant that runs on a Lolin D32 (ESP32) microcontroller. It was designed to display indoor and outdoor temperature, humidity, pressure, and weather conditions on a battery-powered device.

Key features:

• Battery and 5 V input voltage measurement using ADC (through a resistor network).
• Battery percentage estimation with nonlinear calibration
• Automatic day/night deep sleep control
• Home Assistant event logging for voltage and sleep cycles
• OTA updates and encrypted API communication
• Because existing code and enclosures did not meet my requirements, I combined multiple ESPHome projects, wrote custom configuration, and had a custom case designed on Fiverr.

Hardware Used

• Display: Waveshare 2.9" E-Ink Display (V2, R2), 296x128 px, partial refresh, SPI interface
• Microcontroller: Lolin D32 (ESP32-based)
• Battery: Single-cell LiPo, monitored via ADC
• Case: Custom-designed and printed via Fiverr
• Resistors: Voltage divider networks for battery and 5V sensing
• Miscellaneous: 200Ω resistor for onboard LED, JST connectors, wiring

Wiring Diagram

Power & Dividers (left)                             ESP32 (center)             E-Ink Display (right)
───────────────────────────                   ────────────────────────      ─────────────────────────────
          +5V supply                            ┌──────────────────┐            Waveshare 2.9" v2-r2
              |                                 │      ESP32       │              (3.3V logic)
           [20kΩ]                               │                  │
              |                                 │  GPIO18 ──────────────── CLK  ─────────────► SCK
          ──● Node A (GPIO36 sense) ────────────┤◄─ GPIO36 (ADC 5V)|        (SPI clock)
              |                                 │                  |
              |                                 │  GPIO23 ──────────────── MOSI ─────────────► DIN
              |                                 │                  |    (SPI data out)
              |                                 │                  |
            (series link)                       │  GPIO15 ───────────────── CS   ─────────────► CS
              |                                 │                  |
          ──● Node B (GPIO39 wake) ─────────────┤◄─ GPIO39 (wakeup)|
              |                                 │                  |
           [30kΩ]                               │  GPIO17 ───────────────── DC   ─────────────► D/C
              |                                 │                  |
            GND                                 │  GPIO16 ───────────────── RST  ─────────────► RST
                                                │                  |
      4.2V (LiPo)                               │  GPIO4  ◄──────────────── BUSY ─────────────◄ BUSY
              |                                 │                  |
           [36kΩ]                               │  3V3  ─────────────────── VCC  ─────────────► VCC (3.3V)
              |                                 │  GND  ─────────────────── GND  ─────────────► GND
          ──● Node C (GPIO32 batt) ─────────────┤◄─ GPIO32 (ADC batt)
              |                                 │                  |
           [100kΩ]                              │  GPIO22 ──► LED (Awake) ──►───┐
              |                                 │                  |       (LED)|
            GND                                 └──────────────────┘            └───[200Ω] GND

Legend:
  [value]   = resistor
  ● Node A  = divider tap for 5V sense (GPIO36)
  ● Node B  = divider mid / wake input (GPIO39)
  ● Node C  = divider tap for LiPo sense (GPIO32)
  LED       = “Awake LED” driven by GPIO22 (add a series resistor if needed)

GPIO39 doubles as a wake pin for deep sleep. GPIO22 drives an LED to indicate awake state. Both battery and 5V input are monitored via resistor dividers.

Power Management

The display is battery-powered and relies on ESPHome's deep sleep functionality:

• Runs for ~1 minute per wake cycle (configurable)
• Daytime sleep of ~15 minutes between updates
• Night mode enters 8-hour deep sleep after 10 PM
• ESP32 is underclocked to 80 MHz for power savings

Display Layout

• Top-left shows indoor temperature and humidity.
• Top-right contains a battery indicator with charging status.
• Middle section displays outdoor temperature, humidity, and pressure.
• Bottom section shows the timestamp of the last update.

Software (ESPHome)

The configuration uses ESPHome to pull data directly from Home Assistant entities. Battery voltage is displayed using a nonlinear LiPo discharge curve. The code includes logic for day/night cycles, custom refresh rates, and battery percentage calculations.

Case

Since no suitable enclosure existed, I commissioned a custom design via Fiverr. The case supports the display, microcontroller, and battery while remaining easy to open for maintenance. STL files are included in the repository.

Credits and Inspiration

• ESPHome Feature Requests #1109
• kotope/esphome_eink_dashboard
• hanspeda/esphome_homeassistant_display
• Plawasan’s E-Ink Gist

Getting Started

1. Clone this repository:

   https://github.com/whitakerz/Battery-ESP32.git

2. Flash the ESPHome config:

   esphome run battery-08-08-25.yaml

3. Connect the device to Home Assistant.
4. Print and assemble the custom case.