ESP32-S3 HA climate¶

A small temperature and humidity sensor that behaves like something you bought: plug it in, scan the QR code on its screen, and it shows up in Home Assistant.

flowchart LR
  SHT40 -->|I2C| ESP32[ESP32-S3]
  ESP32 -->|SPI| TFT[ST7789 screen]
  ESP32 -->|Wi-Fi| HA[Home Assistant]

What you'll end up with¶

Temperature and humidity

In Home Assistant, updated every 10 seconds.
A live screen

240×240 colour display with Wi‑Fi status and climate tiles. Turn it off from Home Assistant with Display.
Setup from your phone

Scan the code, pick your Wi‑Fi, done.
Settings that stick

Survive reboots and power cuts.
Factory reset

Hold BOOT for 5 seconds to start setup again.
No Wi‑Fi password in the firmware

Not in the code and not in this repo.

What the screen shows¶

Mock-up from the firmware: SoftAP QR (no saved Wi‑Fi), then Wi‑Fi status, temp | humidity tiles, IP, and Display-on cue.

Parts¶

	Part	Notes
	ESP32-S3 N16R8 dev board	16 MB flash, 8 MB PSRAM, USB-C
	SHT40 breakout	Temperature and humidity over I2C
	ST7789 240×240 display	Square 8-pin SPI module
	Breadboard and jumper wires	Any solderless breadboard
	USB-C data cable	Charge-only cables won't work
	A computer running Ubuntu 24.04	Builds and flashes the firmware

Wiring is split into short steps under Wire and validate. The full pin map is on Validate.

Tutorial¶

1. Walk through the code

What each block of the firmware does.
2. Build the image

Install ESPHome and compile.
3. Wire and validate

Breadboard, SHT40, display, then a check.
4. Flash the ESP32

Upload over USB and watch it boot.
5. Configure and test

Join Wi‑Fi, add to Home Assistant, test the reset.

The whole firmware is one file: firmware/climate.yaml.