Components

Notes on using ESPhome and cheap, readily available electronic components. Most of this is documented by ESPHome (linked in the info boxes), these are my own notes that also cover some frustrations and pitfalls -- as well as a reference guide for myself (and whoever else).

• Sensors
  • Potentiometer
  • IKEA VINDRIKTNING Particulate matter sensor
  • PN532 (RFID/NFC reader)
    • Send tag_scanned event to Home Assistant
    • Helpful sensors
  • LD2410 mmWave radar
  • Generic PIR
• Displays
  • MAX7219 LED matrix
  • HD44780 LCD display
  • SSD1306 OLED display
  • PCD8544 Display (Nokia 5110/3310)
    • Wiring
    • ESPHome
• References

Sensors

Potentiometer

IKEA VINDRIKTNING Particulate matter sensor

Hacking and improving the cheap IKEA sensor.

PN532 (RFID/NFC reader)

Supports both SPI and I²C for communicate, reads NFC/RFID tag is able to write to (programmable) tags.

One variaton of the PN532 board

The PN532 can use both SPI or I²C to commincate, configured with a dip switch on the module. Some boards will have the table for the dip switch printed on the PCB silkscreen (not mine).

If there is no table on the silkscreen, usually² this is how they are set up:

Send tag_scanned event to Home Assistant

This will send tag_scanned event with the UID of the tag to Home Assistant when a tag is scanned:

pn532_i2c:     # or pn532_spi
  on_tag:
    then:
      - homeassistant.tag_scanned: !lambda 'return x;'

Which will make your tag show up in Home Assistant under /config/tags where you can assign names to them and create automations. Unfortunately its not possible to use the name/friendly name of the tag in an automation trigger, only the UID (tag_id):

automation:
    - alias: my_tag_scanned
      trigger:
        - platform: tag
          tag_id: DE-AD-BE-EF
      condition: []
      action: []

Helpful sensors

When a tag is scanned, the pn532 component will by default write the tag id (and type) to the logger, so you can retrieve it from there using esphome logs for example (or if you have the web_server component enabled you can use the web ui).

But its useful to just add sensors to the ESPHome node showing this information instead (less hassle to read it, and useful for debugging.

text_sensor:
  - platform: template
    id: tag_uid
    name: "${hostname} Tag UID"

binary_sensor:
  - platform: template
    name: "${hostname} Tag scanned"
    id: tag_scanned
    publish_initial_state: true
    # Return last known state, avoids an 'unknown' state on boot
    # Could also use the on_boot trigger (might be better, the lambda is continuisly evaluated)
    lambda: !-
      return {};
    filters:
      - delayed_off: "10s"

Adds a binary_sensor entity that indicates if a tag has just been scanned, and a text_sensor showing the UID of the most recently scanned tag.

pn532_i2c:
  on_tag:
    then:
      # Writes the tag's uid to the text_sensor
      - text_sensor.template.publish:
          id: tag_uid
          state: !lambda 'return x;'

      # Set the binary_sensor to true/on
      # binary_sensor state intead of relying on automations
      - binary_sensor.template.publish:
          id: tag_scanned
          state: ON

  on_tag_removed:
    then:
      # Set the binary_sensor back to false/off.
      - binary_sensor.template.publish:
          id: tag_scanned
          state: OFF

This uses automations provided by the pn532 component in ESPHome (on_tag and on_tag_removed), but it would be preferrable to just use a lambda in the state attribute of the templated text_sensor and binary_sensor.

LD2410 mmWave radar

Lessons learned, and how to use it to detect static presence reliably using different still_energy values to signal on/true and off/false.

Generic PIR

Simple and easy

Displays

MAX7219 LED matrix

HD44780 LCD display

I have some unusual model "2004A-V1.3". Based on the Arduino forum thread and the linked AliExpress page, this is probably an LCD module called SPLC780D that has an onboard I2C adapter/interface called AIP31066. Found a Github repo enjoyneering/LiquidCrystal_I2C with detailed info.

Arduino forum: [https://forum.arduino.cc/t/funky-20x4-lcd-with-interesting-circuitry/1136532/3]

Almost the same: [https://make.net.za/product/20x4-lcd-white-on-blue/]

SSD1306 OLED display

On the Wemos S2 Mini boards (possibly other ESP32 boards as well), this display will only work with the arduino framework:

esp32:
  board: lolin_s2_mini
  variant: ESP32S2
  framework:
    type: arduino

Any GPIO pins can be used on (most?) ESP32 boards

i2c:
  sda: GPIO16
  scl: GPIO18

font:
  - file: "NotoSansMono-Regular.ttf"
    id: notomono24
    size: 24

display:
  - platform: ssd1306_i2c
    model: "SSD1306 128x64"
    address: 0x3C
    lambda: |-
      it.printf(0, 30, id(notomono24), TextAlign::BASELINE_LEFT, "sudo.is");

I've found that the font Noto Sans Mono looks good on this display.

PCD8544 Display (Nokia 5110/3310)

The display that was used in the Nokia 5110 and 3310 phones, the resolution is 84x48 px. It's still available today (and cheap). They are probably displays disassembled from old Nokia phones and then hand-assembled to PCBs with a LED backlight¹¹.

Wiring

Following an example¹² of how the display can be wired to a standard ESP32 dev board:

ESPHome

There is a GitHub issue on the ESPHome repo:

• esphome/issues#1519: PCD 8544 (Nokia 5110/3310) Display all pixels black

References