AHT20 — i2c address & wiring
Low-cost, accurate temperature and humidity sensor.
Key facts
AHT20 at a glance
| i2c address | 0x38 fixed address |
|---|---|
| Logic voltage | 3.3–5 V |
| Type | sensor |
| Part | Aosong AHT20 |
| Ships with | Qwiic, STEMMA QT, Grove |
The chip
What the Aosong AHT20 actually is
Factory-calibrated digital temperature and relative humidity sensor with an i2c interface. Designed for low-power environmental monitoring applications requiring stable, calibrated humidity and temperature measurements.
Watch out: Some listings still ship the older AHT10, which is known to play badly with other devices on a shared bus; the AHT20/AHT21 are the improved, better-calibrated replacements. Either way the 0x38 address is fixed and can't be changed, so no two of them share one bus.
Wiring
How to connect the AHT20
The AHT20 talks i2c at address 0x38. It runs at 3.3–5 V, so match your host's logic level — if your host is 5 V and a board on the bus is 3.3 V-only, add a level shifter. Use the compatibility checker to confirm the exact cable for your setup.
The address is fixed, so two AHT20s can't share a bus directly — the address-conflict guide covers the workarounds (multiplexer, second bus).
Wiring is the usual four: power, ground, SDA and SCL, plus pull-up resistors — almost always already fitted on the breakout. Nothing showing up? Run an i2c scan first; if the bus is silent, the 7-step checklist finds it faster than guessing.
Ecosystems
Plug-together options for the AHT20
AHT20 breakouts ship with Qwiic, STEMMA QT and Grove — keyed 4-pin cables carrying power, ground, SDA and SCL, so there's nothing to solder and nothing to wire backwards. Chain it to the next board and keep going.
Running a mixed bench? Those ecosystems interoperate more than their marketing suggests — see every connector pairing for the cable or adapter you need, or the standards overview for how they compare.
Alternatives
Other environmental boards
Get one
Questions
AHT20 i2c FAQ
What is the AHT20's i2c address?
The AHT20 sits at a fixed address of 0x38. It can't be changed, so two of them can't share one bus without a multiplexer or a second bus.
What voltage does the AHT20 run at?
3.3–5 V logic. That range covers both 3.3 V and 5 V hosts, so it drops onto a Pi, ESP32 or Arduino without a level shifter.
Can I use two AHT20s on one i2c bus?
Not directly — every AHT20 answers to 0x38, so two on one bus would collide. Use a TCA9548A multiplexer to give each its own channel, or put the second one on a separate bus.
Does the AHT20 work with Qwiic and STEMMA QT and Grove?
Yes — AHT20 breakouts ship with Qwiic / STEMMA QT / Grove, so it plugs straight in with no soldering. Mixing ecosystems? The compatibility checker gives you the exact cable or adapter.
What should I watch out for with the AHT20?
Some listings still ship the older AHT10, which is known to play badly with other devices on a shared bus; the AHT20/AHT21 are the improved, better-calibrated replacements. Either way the 0x38 address is fixed and can't be changed, so no two of them share one bus.