1. Walk through the code¶

The firmware is one ESPHome file: firmware/climate.yaml. You describe the hardware and behaviour in YAML; ESPHome turns that into firmware.

You don't need to memorise the file. The point is to know which block to open when you want to change something.

How the pieces connect¶

flowchart LR
  S["sensor<br/>SHT40"] -->|readings| A[api] -->|entities| HA[Home Assistant]
  S -->|readings| D[display]
  W[wifi] -->|page when unprovisioned| D
  W -.- N[(NVS)]

The display defaults to readings. The QR setup page appears only when no home Wi‑Fi is saved yet (first boot or after factory reset). A short drop keeps the readings page and turns the Wi‑Fi icon off. The dotted line is where the chip stores your home Wi‑Fi details (NVS), never this file.

The blocks¶

ESP32

substitutions esphome esp32 psram logger
Home Assistant

api ota dashboard_import
Wi‑Fi setup

wifi captive_portal (+ Improv in YAML, not walked through)
Sensors

i2c sensor
Display

spi output light switch font qr_code display
Factory reset

button binary_sensor

Where to change things¶

If you want to change…	Open
Setup hotspot name or password	ESP32 → `substitutions`
How often the sensor reads	Sensors → `update_interval`
Screen colours, layout or text	Display → `pages`
Which pins are used	Sensors / Display (same pins as Wire)
Reset hold time	Factory reset → `binary_sensor`

Next: ESP32