Raspberry Pi Pico and AHT20 Sensor circuitpython example

In this article we connect a AHT20 Temperature & Humidity Sensor to a Raspberry Pi Pico running Circuitpython

Sensor Information

AHT20, as a new generation of temperature and humidity sensors, has established a new standard in size and intelligence. It is embedded in a double row flat no-lead package suitable for reflow soldering, with a bottom of 3 x 3 mm and a height of 1.0 mm.

The sensor outputs calibrated digital signals in standard IAHT20, as a new generation of temperature and humidity sensors, has established a new standard in size and intelligence.

It is embedded in a double row flat no-lead package suitable for reflow soldering, with a bottom of 3 x 3 mm and a height of 1.0 mm.

The sensor outputs calibrated digital signals in standard I²C format. AHT20 is equipped with a newly designed ASIC chip, an improved MEMS semiconductor capacitive humidity sensing element and a standard on-chip temperature sensing element.

Supply voltage	DC : 2.0 – 5.5V
Measuring range (humidity)	0 ~ 100% RH
Measuring range (temperature)	-40 ~ + 85 ℃
Humidity accuracy	± 2 % RH ( 25 ℃ )
Temperature accuracy	± 0.3 ℃
Resolution	temperature: 0.01℃ Humidity: 0.024%RH
Response time	temperature: 5s humidity: 8s 1/e (63%)
Output signal	I2C signal

This is the sensor that I bought

 

Parts Required

The sensor you can pick up in the $6 price range – you can connect to the sensor using a standard header the classic dupont style jumper wire.

I used a Qwiic cable – since a few sensors seem to use these but this is optional

Name	Link
Pico	Raspberry Pi Pico Development Board
AHT20	AHT20 Temperature and Humidity Sensor Module High-precision Humidity Sensor https://shop.pimoroni.com/products/adafruit-sensirion-sht40-temperature-humidity-sensor-stemma-qt-qwiic
Connecting cables	Aliexpress product link Lysee 3D Printer Parts & Accessories – AHT20 Temperature and Humidity Sensor Module DHT11 Upgrade I2C XD Humidity Sensor Probe – (Color: Green) Ebay link

 

Schematic/Connection

I used the Adafruit AHT20 sensor and in this case used the Stemma connection

For the STEMMA QT cables, it uses the Qwiic convention:

Black for GND
Red for V+
Blue for SDA
Yellow for SCL

So color coded for ease of use, this layout shows a connection to the module

Code Example

I used Thonny for development

The following is based on a library , I copied the adafruit_sht4x.mpy library for this device to the lib folder on my RP2040 – https://circuitpython.org/libraries

This is the basic example which comes with the library

[codesyntax lang=”python”]

import time
import board
import adafruit_ahtx0
import busio

# Create sensor object, communicating over the board's default I2C bus
#i2c = board.I2C()  # uses board.SCL and board.SDA
i2c = busio.I2C(scl=board.GP1, sda=board.GP0)
sensor = adafruit_ahtx0.AHTx0(i2c)

while True:
    print("\nTemperature: %0.1f C" % sensor.temperature)
    print("Humidity: %0.1f %%" % sensor.relative_humidity)
    time.sleep(2)

[/codesyntax]

Output

Here is what I saw in Thonny REPL window

Temperature: 19.4 C
Humidity: 61.8 %

Temperature: 19.4 C
Humidity: 61.8 %

Temperature: 19.4 C
Humidity: 61.8 %

Temperature: 21.8 C
Humidity: 62.6 %

Temperature: 21.8 C
Humidity: 62.6 %

Links

Product download pdf