ESP32-C6 climate sensor

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A handful of cheap climate sensors beats one expensive hub sensor in the wrong corner of the house. This pack is a single-board recipe: ESP32-C6 Super Mini, AHT20 on I²C, ESPHome native API, Home Assistant discovery.

Wi-Fi credentials stay in your ESPHome secrets file. Never paste SSIDs, PSKs, API keys, or OTA passwords into a published YAML.

What problem it solves

You want a temperature and humidity number in a closet, a crawl space, a garage, or a studio, without buying another brand-name sensor or hub. Copy the YAML once per room, change a few substitutions, and each board shows up in Home Assistant with the room’s name on it.

What you get working

Temperature and humidity entities named after the room you set (for example “Office Temperature”), updated every 60 seconds by default.
Calibration offsets for temperature and humidity, so you can match a reference thermometer without editing filters by hand.
Diagnostics: Wi-Fi signal and uptime sensors, plus a restart button, so a board in a crawl space is easy to check.
Fallback hotspot: if Wi-Fi fails, the board starts its own access point with a captive portal so you can fix the credentials.

Hardware notes

Board. ESP32-C6 Super Mini. Leave these pins alone: GPIO8 (onboard LED and boot strap), GPIO9 (BOOT button and strap), GPIO12 and GPIO13 (USB D− and D+), and GPIO15 (strap). The pack uses GPIO0 and GPIO1 for I²C.
Sensor. AHT20 module. Some listings sold as “AHT20” are AHT10-compatible; ESPHome’s aht10 platform with variant: AHT20 covers both if the address is right (usually 0x38).
Power. Power the board from USB-C, or from an external 5 V supply on the 5V pin — not both at once. The AHT20 always takes 3.3 V from the board’s 3V3 pin, never 5 V.
Placement. The board and a USB charger both make heat. Keep the sensor at the vent end of the case, away from the board, and out of direct sun.

Wiring

Use 3.3 V, not 5 V, on the AHT20.

AHT20	ESP32-C6 Super Mini
VIN	3V3
GND	GND
SDA	GPIO0
SCL	GPIO1

Snippet

Trimmed from the pack YAML. Room names, pins, and offsets are substitutions:

substitutions:
  device_name: climate-office
  friendly_name: Office climate
  room: Office
  sda_pin: GPIO0
  scl_pin: GPIO1
  update_every: 60s
  temp_offset: "0.0"
  humidity_offset: "0.0"

esp32:
  board: esp32-c6-devkitc-1
  framework:
    type: esp-idf

i2c:
  sda: ${sda_pin}
  scl: ${scl_pin}
  scan: true

sensor:
  - platform: aht10
    variant: AHT20
    address: 0x38
    update_interval: ${update_every}
    temperature:
      name: "${room} Temperature"
      filters:
        - offset: ${temp_offset}
    humidity:
      name: "${room} Humidity"
      filters:
        - offset: ${humidity_offset}
# Wi-Fi, API, fallback hotspot, diagnostics, and restart button: full YAML in the pack

The pack YAML uses !secret for Wi-Fi, API encryption, and OTA. Substitute your own secrets locally.

Setup outline

Wire the AHT20 to the board as in the table. Double-check 3V3, not 5V.
Copy secrets.example.yaml to secrets.yaml in your ESPHome folder (or merge the keys into the one you have) and fill in your own values.
Create a new device in ESPHome, paste the pack YAML, and change device_name, friendly_name, and room. Every board needs its own device_name.
Flash over USB the first time. In the logs, the I²C scan should find a device at 0x38. Later updates go over Wi-Fi.
Accept the device in Home Assistant (Settings → Devices & services). Rename entities to a generic room name you will not mind publishing later.
Calibrate: leave the board next to a thermometer you trust for an hour, then set temp_offset and humidity_offset and flash again.
Print the case, put the sensor near the vent slots, and mount it where you want the reading.

Troubleshooting

0x38 not found. Swap SDA/SCL, check 3.3 V, try 4.7 kΩ pull-ups if the module does not include them.
Reads a degree or two high. The sensor is picking up heat from the board, a USB charger, or sun. Move it to the vent end of the case, relocate the board, then fine-tune with temp_offset.
Board not joining Wi-Fi. 2.4 GHz only; the C6 will not see a 5 GHz SSID. Keep the SSID out of git — wifi_ssid / wifi_password in secrets.yaml. If it still fails, join the fallback hotspot and fix the credentials there.
Two boards fight over one device. Both use the same device_name. Give each board its own name and flash again.
API encryption mismatch. Delete the stale device in HA and re-adopt after you rotate the key.

Enclosure

The pack includes a two-part case (base and lid) with vent slots. Print in PETG or PLA, 0.2 mm layers, no supports; the lid presses onto the base. Use PETG if the sensor lives in a garage or porch; PLA is fine indoors.