# Adafruit HDC1008 Temperature and Humidity Sensor Breakout ## Overview ![](https://cdn-learn.adafruit.com/assets/assets/000/026/522/medium800/adafruit_products_2635_iso_ORIG.jpg?1436991746) It's summer and you're sweating and your hair's all frizzy and all you really want to know is why the weatherman said this morning that today's relative humidity would max out at a perfectly reasonable 52% when it feels more like 77%. Enter the **HDC1008 Temperature + Humidity Sensor** - the best way to prove the weatherman wrong! ![](https://cdn-learn.adafruit.com/assets/assets/000/026/524/medium800/adafruit_products_2635_quarter_ORIG.jpg?1436991776) This I2C digital humidity sensor is a fairly accurate and intelligent alternative to the much simpler [Humidity and Temperature Sensor - SHT15 Breakout](https://www.adafruit.com/products/1638) It has a typical accuracy of ±4% with an operating range that's optimized from 10% to 80% RH. Operation outside this range is still possible - just the accuracy might drop a bit. The temperature output has a typical accuracy of ±0.2°C from -20~85°C. The HDC1008 sensor chip has 2 address-select pins, so you can have up to 4 shared on a single I2C bus. It's also 3-5V power and logic safe so you don't need any level shifters or regulators to use with a 5V or 3V microcontroller ![](https://cdn-learn.adafruit.com/assets/assets/000/026/523/medium800/adafruit_products_2635_kit_RESIZE.jpg?1436991768) Such a lovely chip, but only available in a tiny BGA package. So we spun up a breakout board with the chip and some extra passive components to make it easy to use. Each order comes with one fully assembled and tested PCB breakout and a small piece of header. You'll need to solder the header onto the PCB but it's fairly easy and takes only a few minutes even for a beginner. **Please note:** TI has indicated that there's a 'settling' effect for the humidity and that you will need to re-hydrate the sensor once you receive it. To rehydrate it, place it in a location with 85% humidity for 24 hours or 60% humidity for 10 days. # Adafruit HDC1008 Temperature and Humidity Sensor Breakout ## Pinouts The HDC1008 is a I2C sensor. That means it uses the two I2C data/clock wires available on most microcontrollers, and can share those pins with other sensors as long as they don't have an address collision. For future reference, the default I2C address is **0x40** but you can adjust it by connecting the address pins to Vin ('high' logic votlage), for four possible addresess: **0x40, 0x41, 0x42** or **0x43** ![](https://cdn-learn.adafruit.com/assets/assets/000/026/527/medium800/adafruit_products_pinout.jpg?1436991932) ## Power Pins: - **Vin** - this is the power pin. Unlike many sensors, this chip can be powered by 3-5 VDC, so there is no voltage regulator on board. Simply power the board with the same power as the logic level of your microcontroller - e.g. for a 5V micro like Arduino, use 5V. For a 3V ARM processor, use 3V - **GND** - common ground for power and logic ## I2C Logic pins: - **SCL** - I2C clock pin, connect to your microcontrollers I2C clock line. 3-5V logic OK - **SDA** - I2C data pin, connect to your microcontrollers I2C data line. 3-5V logic OK # Optional Pins These are pins you don't need to connect to unless you want to! - **RDY** - This is the interrupt/'ready' pin from the HDC100x. The chip has some capability to 'alert' you when data is ready to be read from the sensor. We don't use this pin in our library but it's available if you need it! It is **open collector** so you need to use a pull-up resistor if you want to read signal from this pin. - **A0 A1** - These are the address select pins. Since you can only have one device with a given address on an i2c bus, there must be a way to adjust the address if you want to put more than one HDC100X on a shared i2c bus. The A0/A1 pins set the bottom 2 bits of the i2c address. There are pull-down resistors on the board so connect them to Vin to set the bits to '1'. They are read on power up, so de-power and re-power to reset the address The default address is **0x40** and the address can be calculated by 'adding' the **A0/A1** to the base of 0x40 **A0** sets the lowest bit with a value of **1** , **A1** sets the middle bit with a value of **2.** The final address is **0x40 + A1 + A0**. So for example if **A1** is tied to Vin and **A0** is tied to Vin, the address is **0x40 + 2 + 1 = 0x43.** If only A0 is tied to Vin, the address is **0x40 + 1 = 0x41** If only A1 is tied to Vin, the address is **0x42 + 2 = 0x42** Warning: # Adafruit HDC1008 Temperature and Humidity Sensor Breakout ## Assembly ![](https://cdn-learn.adafruit.com/assets/assets/000/026/528/medium800/adafruit_products_2635_kit_ORIG.jpg?1436992402) ## Prepare the header strip: Cut the strip to length if necessary. It will be easier to solder if you insert it into a breadboard - **long pins down** ![adafruit_products_header.jpg](https://cdn-learn.adafruit.com/assets/assets/000/026/529/medium640/adafruit_products_header.jpg?1436992609) ## Add the breakout board: Place the breakout board over the pins so that the short pins poke through the breakout pads ![adafruit_products_place.jpg](https://cdn-learn.adafruit.com/assets/assets/000/026/530/medium640/adafruit_products_place.jpg?1436992618) ## And Solder! Be sure to solder all pins for reliable electrical contact. _(For tips on soldering, be sure to check out our_ [_Guide to Excellent Soldering_](http://learn.adafruit.com/adafruit-guide-excellent-soldering)_)._ ![adafruit_products_solder1.jpg](https://cdn-learn.adafruit.com/assets/assets/000/026/531/medium640/adafruit_products_solder1.jpg?1436992628) ![adafruit_products_solder2.jpg](https://cdn-learn.adafruit.com/assets/assets/000/026/532/medium640/adafruit_products_solder2.jpg?1436992633) ![adafruit_products_solder3.jpg](https://cdn-learn.adafruit.com/assets/assets/000/026/533/medium640/adafruit_products_solder3.jpg?1436992640) You're done! Check your solder joints visually and continue onto the next steps ![adafruit_products_done.jpg](https://cdn-learn.adafruit.com/assets/assets/000/026/534/medium640/adafruit_products_done.jpg?1436992651) # Adafruit HDC1008 Temperature and Humidity Sensor Breakout ## Wiring & Test You can easily wire this breakout to any microcontroller, we'll be using an Arduino. For another kind of microcontroller, just make sure it has I2C, then port the code - its pretty simple stuff! ![](https://cdn-learn.adafruit.com/assets/assets/000/026/535/medium800/adafruit_products_wiring.jpg?1436992690) - Connect **Vin** to the power supply, 3-5V is fine. Use the same voltage that the microcontroller logic is based off of. For most Arduinos, that is 5V - Connect **GND** to common power/data ground - Connect the **SCL** pin to the I2C clock **SCL** pin on your Arduino. On an UNO & '328 based Arduino, this is also known as **A5** , on a Mega it is also known as **digital 21** and on a Leonardo/Micro, **digital 3** - Connect the **SDA** pin to the I2C data **SDA** pin on your Arduino. On an UNO & '328 based Arduino, this is also known as **A4** , on a Mega it is also known as **digital 20** and on a Leonardo/Micro, **digital 2** The HDC1008 has a default I2C address of **0x40** # Download Adafruit\_HDC1000 To begin reading sensor data, you will need to download Adafruit\_HDC1000 library from the Arduino library manager. Open up the Arduino library manager: ![](https://cdn-learn.adafruit.com/assets/assets/000/084/198/medium800/adafruit_products_library_manager_menu.png?1573772268) Search for the  **Adafruit HDC1000** library and install it ![](https://cdn-learn.adafruit.com/assets/assets/000/084/199/medium800/adafruit_products_hdc1000.png?1573772329) We also have a great tutorial on Arduino library installation at: [http://learn.adafruit.com/adafruit-all-about-arduino-libraries-install-use](http://learn.adafruit.com/adafruit-all-about-arduino-libraries-install-use "Link: http://learn.adafruit.com/adafruit-all-about-arduino-libraries-install-use") # Load Demo Open up **File-\>Examples-\>Adafruit\_HDC1000**** -\>HDC1000test** and upload to your Arduino wired up to the sensor ![](https://cdn-learn.adafruit.com/assets/assets/000/026/536/medium800/adafruit_products_test.png?1436993196) Thats it! Now open up the serial terminal window at 9600 speed to begin the test. ![](https://cdn-learn.adafruit.com/assets/assets/000/026/537/medium800/adafruit_products_out.png?1436993358) **Please note:** TI has indicated that there's a 'settling' effect for the humidity and that you will need to re-hydrate the sensor once you receive it. To rehydrate it, place it in a location with 85% humidity for 24 hours or 60% humidity for 10 days. # Library Reference The library we have is simple and easy to use You can create the **Adafruit\_HDC1000** object with: ```auto Adafruit_HDC1000 hdc = Adafruit_HDC1000() ``` There are no pins to set since you must use the I2C bus! Then initialize the sensor with: ```auto hdc.begin() ``` if you aren't using the default 0x40 i2c address, you can pass in the i2c address to **begin** to have it use that one instead. ```auto hdc.begin(0x42) ``` this function returns **True** if the sensor was found and responded correctly and **False** if it was not found Once initialized, you can query the temperature in °C with ```auto hdc.readTemperature() ``` Which will return floating point (decimal + fractional) temperature. You can convert to Fahrenheit by multiplying by 1.8 and adding 32 as you have learned in grade school! Reading the humidity is equally simple. Call ```auto hdc.readHumidity() ``` to read the humidity also as a floating point value between 0 and 100 (this reads % humidity) # Adafruit HDC1008 Temperature and Humidity Sensor Breakout ## Downloads # Files - [Datasheet for the HDC1008 sensor on the breakout](http://www.adafruit.com/datasheets/hdc1008.pdf) - [Arduino driver Library](https://github.com/adafruit/Adafruit_HDC1000_Library) - [EagleCAD PCB files on GitHub](https://github.com/adafruit/Adafruit-HDC1008-Breakout-PCB) - [Fritzing object in the Adafruit Fritzing Library](https://github.com/adafruit/Fritzing-Library) # Schematics ![](https://cdn-learn.adafruit.com/assets/assets/000/026/539/medium800/adafruit_products_schem.png?1436993844) # PCB Print Dimensions in Inches! ![](https://cdn-learn.adafruit.com/assets/assets/000/026/538/medium800/adafruit_products_print.png?1436993832) ## Related Guides - [Adafruit TMAG5273 3D Hall Effect Magnetometer Breakout](https://learn.adafruit.com/adafruit-tmag5273-3d-hall-effect-magnetometer-breakout.md) - [Adafruit PiCowbell Adalogger for Pico](https://learn.adafruit.com/adafruit-picowbell-adalogger-for-pico.md) - [Adafruit Feather M4 CAN Express](https://learn.adafruit.com/adafruit-feather-m4-can-express.md) - [74HC595 Shift Register](https://learn.adafruit.com/74hc595.md) - [Adafruit VEML7700 Ambient Light Sensor](https://learn.adafruit.com/adafruit-veml7700.md) - [Adafruit VCNL4040 Proximity Sensor](https://learn.adafruit.com/adafruit-vcnl4040-proximity-sensor.md) - [Adafruit MagTag](https://learn.adafruit.com/adafruit-magtag.md) - [Articulating Retina Monitor](https://learn.adafruit.com/articulating-retina-monitor.md) - [Adafruit RGB Matrix FeatherWings](https://learn.adafruit.com/rgb-matrix-featherwing.md) - [Adafruit NeoSlider](https://learn.adafruit.com/adafruit-neoslider.md) - [Adafruit RS232 Pal](https://learn.adafruit.com/adafruit-rs232-pal.md) - [A REST API for Arduino & the CC3000 WiFi Chip](https://learn.adafruit.com/a-rest-api-for-arduino-and-the-cc3000-wifi-chip.md) - [Adafruit Grayscale 1.5" 128x128 OLED Display](https://learn.adafruit.com/adafruit-grayscale-1-5-128x128-oled-display.md) - [Compost Friend!](https://learn.adafruit.com/compost-optimization-machine.md) - [Adafruit PyPortal Titano](https://learn.adafruit.com/adafruit-pyportal-titano.md)