Lilygo T5-4.7 E-paper display & ESPhome

A nerd friend bought me a LILYGO E-paper display¹, in the exact hope that I’d end up going down the rabbit hole of Smart Things. I have gone down this bloody rabbit hole. I’ve always been a sucker for data, and I aspire to heating my home more efficiently by measuring temperatures round the house and seeing how they change as I change demand.

This is not a place of honour. It’s a place of a lot of YAML and black magic. It’s pretty cool when it works though:

The board is a micro with Wi-Fi and a big-enough E-Paper Display (EPD)
I can reconfigure it via context-aware text editor in the browser
Push updates (also from the browser)
Do some reasonably complex data processing and image/text rastering on the micro itself
Control it from either a self-hosted server on the micro or from Home Assistant

Details

I’ve done things in Docker for the moment, although they may not end up staying there. My Synology NAS can run containers pretty painlessly, and understands Docker Compose². The relevant parts of the config file is at the bottom of this post. Due to both services using mDNS for their autodiscovery, host networking is required.

On starting Home Assistant and browsing to it, it’ll ask a bunch of obvious questions and set itself up. Home Assistant and ESPhome will then auto-discover each other.

To actually program the Lilygo for the first time, you need to have it connected via USB. Chrome can actually do this if you set up TLS for the dashboard, but I found it simpler to to all the configuration and setup in dash, and then you can use the Manual Download option and I ran esptool myself on my desktop (pip3 install --user esptool). Don’t use the ’legacy’ file.

esptool.py --chip esp32 -p /dev/ttyACM0 write_flash 0x0 lilygo-factory.bin

After this it won’t need a physical connection again.

The configuration file I’m currently using is shown below, and I will change it a lot I think, but I needed to start somewhere and I’m happy with this as something usable for a bit. It features:

Not one but TWO sizes of fonts
Icons to look pretty and clean
Current temperature
Daily high and low temperature
Graph of the temperature over the last 6h
Current exchange rate between the UK and Canada
Sunrise/sunset time
Text string controllable from HA
Buttons are visible in HA (not sure if this is useful, mind)

The sunrise/sunset one is a bit of a pain. Technically I think the simplest thing is to let ESPhome calculate this in its own Sun component, however as there’s one set up in HA and I don’t want to hardcode destinations everywhere³.

TODO

This isn’t “perfect” yet, but I haven’t worked out exactly what it needs to do. I have some vague ideas:

Go to sleep and save some power
Get prettier, like in this fancy config
Slap a battery in it (ordered one!)
Print a case!
Stop the EPD fading out when losing power⁴, maybe by calibrating
Maybe try a new way of controlling the display, keeping an eye on this bug
Log to MQTT, but I’m a bit worried this might confuse HA
Have some pages and cycle through them?

Docker compose snippet

The config here is starting Home Assistant and ESPhome. I originally had HA depend on ESPhome but I realised that while I’d prefer HA to come up last it doesn’t actually require it and certainly shouldn’t be prevented from starting.

I don’t really like using host mode networking but it’s needed by default for mDNS and while apparently one can work round that, I haven’t tried it yet.

version: '3'
  homeassistant:
    container_name: homeassistant
    image: "ghcr.io/home-assistant/home-assistant:stable"
    volumes:
      - /volume1/docker/homeassistant:/config
      - /etc/localtime:/etc/localtime:ro
    restart: unless-stopped
    privileged: true # for when we have USB
    network_mode: host # for mDNS
    depends_on:
      - esphome
  esphome:
    container_name: esphome
    image: ghcr.io/esphome/esphome
    volumes:
      - /volume1/docker/esphome:/config
      - /etc/localtime:/etc/localtime:ro
    restart: unless-stopped
    network_mode: host # required for mDNS
    environment:
      - USERNAME=xxx
      - PASSWORD=xxx
    healthcheck:
      test: "curl -f http://localhost:6052/version -A HealthCheck || exit 1"
      interval: 30s
      timeout: 30s

Final configuration

This requires entries in the secrets.yaml for all the !secret directives.

substitutions:
  esp_name: lilygo
  font_small: "48"
  font_big: "100"

esphome:
  name: ${esp_name}
  comment: "E-paper display"
  friendly_name: lilygo

esp32:
  board: esp32dev
  framework:
    type: arduino

logger:
  level: INFO

# To connect *to* HA *from* lilygo
api:
  encryption:
    key: !secret ha_key

ota:
  password: !secret lilygo_ota

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password

  # Enable fallback hotspot (captive_portal node) in case wifi connection fails
  ap:
    ssid: "Lilygo Fallback Hotspot"
    password: !secret fallback

captive_portal:

external_components:
  - source: github://tiaanv/esphome-components
    components:
      - "t547"

time:
  - platform: homeassistant
    id: ntp
    timezone: "America/Toronto" # Picking up the timezone from HA would be nice

# Setting these buttons with names auto-exposes them to HA
button:
  - platform: restart
    name: "${esp_name} Restart"

  - platform: template
    name: "${esp_name} Refresh"
    icon: "mdi:update"
    on_press:
      then:
      - component.update: t5_disp

# Fonts are downloaded from Google at build time, which is pretty neat.
# Get codepoint values from the Google Fonts website.
font:
  - file: "gfonts://Roboto"
    id: roboto
    size: $font_small
  - file:
      type: gfonts
      family: Roboto
      weight: 500
    id: din_big
    # Glyphs are prerastered, choose them early to save flash
    glyphs: " C$+-0123456789.:"
    size: $font_big
  - file: 'gfonts://Material+Symbols+Outlined'
    id: font_icons_small
    size: $font_small
    glyphs: # also as a list
      - "\U0000E1C6" # Sunrise
      - "\U0000EF44" # Sunset
      - "\U0000F582" # Temperature High
      - "\U0000F581" # Temperature Low
  - file: 'gfonts://Material+Symbols+Outlined'
    id: font_icons_big
    size: $font_big
    glyphs:
      - "\ue1ff" # device_thermostat
      - "\ueb70" # currency exchange

binary_sensor:
  - platform: status
    name: "status"
    # Setting up the buttons here to refresh the display
    # (for experimenting with sleep mode) and to flip between
    # pages on the display.  Only one is defined at the bottom
    # right now
  - platform: gpio
    pin:
      number: GPIO39
      inverted: true
    internal: true
    on_press:
      then:
        - component.update: t5_disp
    name: "Button 1"
  - platform: gpio
    pin:
      number: GPIO34
      inverted: true
    name: "Button 2"
    internal: true
    on_press:
      then:
        - display.page.show_previous: t5_disp
        - component.update: t5_disp
  - platform: gpio
    pin:
      number: GPIO35
      inverted: true
    name: "Button 3"
    internal: true
    on_press:
      then:
        - display.page.show_next: t5_disp
        - component.update: t5_disp

# Import some strings from HA - annoyingly we can't import
# times from HA *as times* and strftime them, so these need
# a template/helper on HA
text_sensor:
  - platform: homeassistant
    entity_id: sensor.next_rising_time
    id: sunrise
  - platform: homeassistant
    entity_id: sensor.next_setting_time
    id: sunset

# This bit basically defines a textbox that HA can fill
# called 'alert' that the micro won't update itself (because
# nothing will) but will prompt a redraw of the screen
text:
  mode: text
  name: alert
  id: alert
  platform: template
  optimistic: True
  # maybe add a startup set of this state so HA doesn't say Unknown
  update_interval: never
  on_value:
    then:
      - component.update: t5_disp

sensor:
  - platform: homeassistant
    name: "Current temperature"
    entity_id: sensor.gatineau_temperature
    id: temp
  - platform: homeassistant
    name: "Daily high"
    entity_id: sensor.gatineau_high_temperature
    id: daily_high
  - platform: homeassistant
    name: "Daily low"
    entity_id: sensor.gatineau_low_temperature
    id: daily_low
  - platform: homeassistant
    name: "GBP CAD"
    entity_id: sensor.gbp_cad
    id: gbp_cad
    on_value: # Actions to perform once data for the last sensor has been received
      then:
        - script.execute: all_data_received

script:
  - id: all_data_received
    then:
      - component.update: t5_disp

graph:
  # Show bare-minimum auto-ranged graph.  It is not saved so
  # any power loss or restart loses it. It'll take a while to fill
  - id: temp_graph
    sensor: temp
    duration: 6h
    x_grid: 1h
    y_grid: 5.0     # degC/div
    width: 400
    height: 400

display:
  - platform: t547
    id: t5_disp
    rotation: 90
    update_interval: 5min
    pages:
      - id: weather
        lambda: |-
          it.print(  40,  60, id(font_icons_big), TextAlign::CENTER_LEFT, "\ue1ff");
          it.printf(130,  60, id(din_big),        TextAlign::CENTER_LEFT, "%3.1fC", id(temp).state);
          it.graph((it.get_width() / 2)-200, 140, id(temp_graph)); // no support for ImageAlign in graph()
          it.print(  70, 600, id(font_icons_small), TextAlign::CENTER_LEFT, "\U0000F582");
          it.printf(260, 600, id(roboto),  TextAlign::CENTER_RIGHT, "%.1fC", id(daily_high).state);
          it.print(  70, 660, id(font_icons_small), TextAlign::CENTER_LEFT, "\U0000F581");
          it.printf(260, 660, id(roboto),  TextAlign::CENTER_RIGHT, "%.1fC", id(daily_low).state);
          it.print( 270, 600, id(font_icons_small), TextAlign::CENTER_LEFT, "\uE1C6");
          it.print( 340, 600, id(roboto),  TextAlign::CENTER_LEFT, id(sunrise).state.c_str());
          it.print( 270, 660, id(font_icons_small), TextAlign::CENTER_LEFT, "\uEF44");
          it.print( 340, 660, id(roboto),  TextAlign::CENTER_LEFT, id(sunset).state.c_str());
          it.printf(130, 800, id(din_big), TextAlign::CENTER_LEFT, "C$ %.2f", id(gbp_cad).state);
          it.print(  20, 880, id(roboto),  TextAlign::TOP_LEFT, id(alert).state.c_str());          
    # This prints a thermometer and the current temperature
    # Then a temperature graph
    # Then the daily high and low temperatures to the left
    #   and sunrise/sunset to the right
    # Next is the GBP/CAD exchange rate
    # Finally that arbitrary string

Actually they don’t make it any more, it’s, uh, sat on my shelf a bit. Now there’s this one but I’m not sure what the esphome support is like. ↩︎
It is just an expensive Linux box after all. You’d hope. ↩︎
Although maybe a template in ESPhome might help here. ↩︎
This might be a better EPD component but as the author made an esphome fork rather than a component library I think need to check it out differently. ↩︎

Details¶

TODO¶

Docker compose snippet¶

Final configuration¶

Details

TODO

Docker compose snippet

Final configuration