Aosong · Integrated circuit

DHT22 / AM2302 Humidity and Temperature Sensor

Humidity and temperature on one wire, in a plastic grille you can read in about ten lines of code. Slow, cheap and everywhere.

1.Pinout diagram

Grille facing you, left to right

DHT22

Pin detail

Hover a pin for its mappings and gotchas. Click to keep it here.

Fig. 1. DHT22 / AM2302 Humidity and Temperature Sensor, 4-pin single row, 2.54 mm. Hover or tap a signal to light up every pin that carries it.

The one-wire protocol here is not Dallas 1-Wire. The datasheet says so explicitly: it is a custom timing scheme, so it shares no library, no bus and no device addressing with a DS18B20. You cannot put both on one pin.
There is no addressing at all, so one sensor needs one GPIO. Two sensors means two pins.
Read it no faster than once every two seconds. Faster reads return stale data or fail outright, and the sensor self-heats, which biases the temperature it is reporting.
After power-up, wait a second before talking to it. The datasheet asks for this directly, and a read inside that window is the usual cause of a sensor that works only after a reset.
The manufacturer's own connection diagram uses a 1 kOhm pull-up on the data line, not the 4.7 kOhm that most guides repeat. Either works over a short lead; the lower value is the one the maker drew.
Pin 3 is not connected. The datasheet's pin table lists it struck through, left from a revision where it was a second ground. Leave it alone.
The timing is tight enough that reads fail on a busy processor with interrupts running. That is the sensor's fault, not yours, and it is why most libraries disable interrupts for the duration of a read.
The DHT11 is the same shape and protocol with worse everything: 1 percent humidity resolution against 0.1, and no negative temperatures. The AM2302 is the DHT22 with a cable instead of pins, red to power, black to ground, yellow to data.

What has to go around the chip before it will run.

Fig. 2. Minimum circuit, drawn from Table 1. Dashed parts are optional. Crossing wires are not connected.

Table 1. External parts, and why each one is there.
Part	Between	Why
1 kOhm	DATA (2) to VCC	Pull-up on the data line, the value the manufacturer's own connection diagram uses. The line idles high and both ends pull it low to talk.
100 nF ceramicoptional	VDD (1) to GND	Supply filtering between VDD and GND, suggested by the datasheet for wave filtering rather than required to function.

That is the whole circuit. Data goes to any GPIO, and the sensor needs a second between power-up and the first read.

Every pin, alias and mapping. This is the table that prints.

Table 2. Pin assignments.

Complete pin reference for DHT22 / AM2302 Humidity and Temperature Sensor
Pin	Name	Also called	Functions	Notes
1	VDD3.3-5.5 V	-	Power supply
2	DATA	-	Single-wire data	Needs a pull-up. Not compatible with Dallas 1-Wire.
3	NC	-	-	Struck through in the datasheet's table. A second ground on an older revision.
4	GND	-	Ground

Found a wrong pin? The whole board is one file, data/boards/dht22.json.