Interfacing AHT10 Temperature & Humidity with ESP32

AHT10 practical reference

A compact I2C temperature/humidity sensor that replaced the DHT11/DHT22 in many designs thanks to its digital calibration and low power draw.

Key specifications

• Supply voltage: 2.2V–5.5V (breakout modules commonly run at 3.3V or 5V via onboard regulation)
• Operating current: ~0.25 mA during measurement, <0.01 mA average in idle/standby
• Humidity range: 0-100% RH
• Humidity accuracy: ±2% RH (typical, 0-100% range)
• Temperature range: -40°C to +85°C
• Temperature accuracy: ±0.3°C (typical)
• Resolution: 0.024% RH, 0.01°C
• Interface: I2C, up to 400kHz (Fast mode)
• I2C address: 0x38 (fixed, not configurable)
• Response time: ~8 seconds to 63% of a step change

Pinout and connection notes

Fixed I2C address — the AHT10 has no address-select pin, so its 0x38 address cannot be changed. If your project needs two AHT10s on one bus, you'll need an I2C multiplexer (e.g. TCA9548A) rather than an address pin trick.

Pull-up resistors — most breakout boards already include their own 10kΩ pull-ups on SDA/SCL. If you're combining several I2C breakouts on one bus, having pull-ups on every single board isn't harmful but is redundant — it just lowers the effective resistance a bit. It only becomes a real problem with many boards stacked at once.

Initialization matters — unlike the DHT11/22, the AHT10 expects a specific init sequence after power-up (a calibration-enable command, typically 0xE1 0x08 0x00) before its first reading is trustworthy. Most libraries (Adafruit_AHTX0, etc.) handle this automatically — if you're talking to it with raw Wire.h calls, check the datasheet command table first.

Check the calibration bit — each status byte returned by the sensor includes a "calibrated" flag. Skip acting on the very first reading after power-up until that bit is set, or you risk reading pre-calibration noise as valid data.

• VCC: Power, 2.2–5.5V DC depending on breakout
• GND: Ground
• SCL: I2C clock line
• SDA: I2C data line

Integration checklist

1. Confirm the exact part number and breakout-board revision.
2. Verify supply voltage, current demand, logic levels, and signal direction against the datasheet.
3. Check controller pin assignments and bus address or interface mode against the example code.
4. Power up with external loads disconnected, then test signals before full integration.
5. If readings or communication fail, check power and ground first, then pin mapping, interface settings, and library initialization.

Troubleshooting and reproducibility

Record the board used, wiring, library/version, supply arrangement, and measured behavior. Use the selected board-specific wiring example as the source of truth. Never assume visually similar modules share identical voltage tolerance or pin order.