Adafruit Feather M0 and SHT40 Temperature & Humidity Sensor circuitpython example

In this article we connect a SHT40 Temperature & Humidity Sensor to an Adafruit Feather M0 running Circuitpython

Sensor Information

This is the next generation of SHT sensor, in the past we have had examples for sensors such as the SHt31 and now we move on to the 4th generation of these

First lets look at some information about the sensor from the manufacturer

The SHT40 builds on a completely new and optimized CMOSens® chip that offers reduced power consumption and improved accuracy specifications. With the extended supply voltage range from 1.08 V to 3.6 V, it’s the perfect fit for mobile and battery-driven applications.

Here is the sensor I purchased from the good folks at Adafruit (via Pimoroni in the UK)

adafruit SHT40

Unlike earlier SHT sensors, this sensor has a true I2C interface for easy interfacing with only two wires (plus power and ground!).

Thanks to the voltage regulator and level shifting circuitry that Adafruit have included on the breakout it is also 3V or 5V compliant, so you can plug it into the 5v of your Arduino without worrying about blowing the thing up – which is always handy.

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
Adafruit Feather M0 Express	Amazon link Ebay link
SHT40	https://www.adafruit.com/product/4885 https://shop.pimoroni.com/products/adafruit-sensirion-sht40-temperature-humidity-sensor-stemma-qt-qwiic
Connecting cables	Aliexpress product link Amazon.com link Ebay link

Schematic/Connection

I used the Adafruit VCNL4040 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

feather and sht40

Code Example

I used Mu 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 Feather M0 Express – https://circuitpython.org/libraries

This is the basic example which comes with the library

[codesyntax lang=”python”]

import time
import board
import adafruit_sht4x

i2c = board.I2C()  # uses board.SCL and board.SDA
sht = adafruit_sht4x.SHT4x(i2c)
print("Found SHT4x with serial number", hex(sht.serial_number))

sht.mode = adafruit_sht4x.Mode.NOHEAT_HIGHPRECISION
# Can also set the mode to enable heater
# sht.mode = adafruit_sht4x.Mode.LOWHEAT_100MS
print("Current mode is: ", adafruit_sht4x.Mode.string[sht.mode])

while True:
    temperature, relative_humidity = sht.measurements
    print("Temperature: %0.1f C" % temperature)
    print("Humidity: %0.1f %%" % relative_humidity)
    print("")
    time.sleep(1)

[/codesyntax]

Output

Here is what I saw in Mu REPL window

Temperature: 22.4 C
Humidity: 45.5 %

Temperature: 27.2 C
Humidity: 46.4 %

Temperature: 28.4 C
Humidity: 47.0 %

Temperature: 28.8 C
Humidity: 47.5 %

Temperature: 29.1 C
Humidity: 48.3 %

Links

https://learn.adafruit.com/introducing-adafruit-stemma-qt/technical-specs

https://www.sensirion.com/en/download-center/humidity-sensors/humidity-sensor-sht4x/