It's half USB Key, half temperature-humidity sensor... it's the Adafruit SHT41 Trinkey. We wanted to make it super-easy to add one of our most popular combination environmental sensors to any computer with a USB A port.

The PCB is designed to slip into any USB A port on a computer or laptop. There's an ATSAMD21 microcontroller on board with just enough circuitry to keep it happy. One pin of the microcontroller connects to a NeoPixel LEDs. Another pin is used as a capacitive touch input on the end. A reset button lets you enter bootloader mode if necessary. That's it!

The SAMD21 can run CircuitPython or Arduino very nicely - both have existing SHT4x, NeoPixel and our FreeTouch (capacitive touch) libraries. Over the USB connection, you can have serial, MIDI, or HID connectivity.

The star of this Trinkey is the SHT41 from Sensirion. Sensirion Temperature/Humidity sensors are some of the finest & highest-accuracy devices you can get. The SHT41 sensor is the fourth generation of I2C temperature and humidity sensor from Sensirion. (They started at the SHT10 and reached the top!). The SHT41 has an excellent ±1.8% typical relative humidity accuracy from 25 to 75% and ±0.2 °C typical accuracy from 0 to 75 °C. Note that the reported temperature may be a few degrees higher than ambient due to self-heating.

The SHT41 Trinkey is perfect for simple projects that want to read the ambient temperature and humidity without any extra wiring, soldering, drivers, or complex software. In fact we even ship the board pre-programmed with code that will print a unique serial number, the temperature, humidity and touch sensor over a serial/COM port in CSV (comma separated value) format, so you can use it immediately.  If you need to measure farther than the computer port, simply use any USB A extension cable.

If you need the 'best' of the SHT4x series, check out the SHT45 Trinkey which has ±1.0% typical relative humidity accuracy from 25 to 75% and ±0.1°C typical accuracy from 0 to 75 °C.

We think it's just an adorable little board, small and durable and inexpensive enough that it could be a first microcontroller board or inspiration for advanced developers to make something simple and fun.

• ATSAMD21E18 32-bit Cortex M0+ - 48 MHz 32 bit processor with 256KB Flash and 32 KB RAM
  
• Native USB supported by every OS - can be used in Arduino or CircuitPython as USB serial console, MIDI, Keyboard/Mouse HID, even a little disk drive for storing Python scripts.
• Can be used with Arduino IDE or CircuitPython
• One RGB NeoPixel LED
• One Capacitive Touchpad
• SHT41 Temperature + Humidity sensor with thermal-isolation cutout
• Reset switch for starting your project code over or entering bootloader mode
• Slim and cute, keychain-friendly!

Technical Details:

SHT41 Specifications & Features

• Relative humidity accuracy: up to ±1.8 %RH
  
• Temperature accuracy: up to ±0.2 °C
• Breakout supply voltage: 3.3 to 5V
• Average bare sensor current: 0.4 μA (at meas. rate 1 Hz)
• Idle bare sensor current: 80 nA
• I2C fast mode plus, CRC checksum
• Operating range: 0…100 %RH, -40…125 °C
• Fully functional in condensing environment
• Variable power heater
• NIST traceability for sensor
• JEDEC JESD47 qualification for sensor
• Mature technology from global market leader Sensirion
• I2C address 0x44
• Product Dimensions: 31.8mm x 11.8mm x 4.5mm / 1.3" x 0.5" x 0.2"

Package Includes:

• 1 x Adafruit 5912 SHT41 Trinkey - USB Temperature and Humidity Sensor