Overview

The long awaited BME680 from Bosch gives you all the environmental sensing you want in one small package. This little sensor contains temperature, humidity, barometric pressure and VOC gas sensing capabilities. All over SPI or I2C, at a great price!

Like the BME280 & BMP280, this precision sensor from Bosch is the can measure humidity with ±3% accuracy, barometric pressure with ±1 hPa absolute accuracy, and temperature with ±1.0°C accuracy. Because pressure changes with altitude, and the pressure measurements are so good, you can also use it as an altimeter with  ±1 meter or better accuracy!

The BME680 takes those sensors to the next step in that it contains a small MOX sensor. The heated metal oxide changes resistance based on the volatile organic compounds (VOC) in the air, so it can be used to detect gasses & alcohols such as Ethanol, Alcohol and Carbon Monoxide and perform air quality measurements. Note it will give you one resistance value, with overall VOC content, it cannot differentiate gasses or alcohols.

Please note, this sensor, like all VOC/gas sensors, has variability and to get precise measurements you will want to calibrate it against known sources! That said, for general environmental sensors, it will give you a good idea of trends and comparisons. We recommend that you run this sensor for 48 hours when you first receive it to "burn it in", and then 30 minutes in the desired mode every time the sensor is in use. This is because the sensitivity levels of the sensor will change during early use and the resistance will slowly rise over time as the MOX warms up to its baseline reading.

For your convenience we've pick-and-placed the sensor on a PCB with a 3.3V regulator and some level shifting so it can be easily used with your favorite 3.3V or 5V microcontroller.

Pinouts

Power Pins:

  • Vin - this is the power pin. Since the sensor chip uses 3 VDC, we have included a voltage regulator on board that will take 3-5VDC and safely convert it down. To power the board, give it the same power as the logic level of your microcontroller - e.g. for a 5V micro like Arduino, use 5V
  • 3Vo - this is the 3.3V output from the voltage regulator, you can grab up to 100mA from this if you like
  • GND - common ground for power and logic

SPI Logic pins:

All pins going into the breakout have level shifting circuitry to make them 3-5V logic level safe. Use whatever logic level is on Vin!

  • SCK - This is the SPI Clock pin, its an input to the chip
  • SDO - this is the Serial Data Out / Master In Slave Out pin, for data sent from the BME680 to your processor
  • SDI - this is the Serial Data In / Master Out Slave In pin, for data sent from your processor to the BME680
  • CS - this is the Chip Select pin, drop it low to start an SPI transaction. Its an input to the chip

If you want to connect multiple BME680's to one microcontroller, have them share the SDI, SDO and SCK pins. Then assign each one a unique CS pin.

I2C Logic pins:

  • SCK - this is also the I2C clock pin, connect to your microcontrollers I2C clock line.
  • SDI - this is also the I2C data pin, connect to your microcontrollers I2C data line.

Leave the other pins disconnected

Assembly

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

Add the breakout board:

Place the breakout board over the pins so that the short pins poke through the breakout pads

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).

You're done! Check your solder joints visually and continue onto the next steps

Arduino Wiring & Test

You can easily wire this breakout to any microcontroller, we'll be using an Arduino compatible. For another kind of microcontroller, as long as you have 4 available pins it is possible to 'bit-bang SPI' or you can use two I2C pins, but usually those pins are fixed in hardware. Just check out the library, then port the code.

I2C Wiring

Use this wiring if you want to connect via I2C interface

By default, the i2c address is 0x77.  If you add a jumper from SDO to GND, the address will change to 0x76.

 

  • 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. For 3.3V logic devices, use 3.3V
  • Connect GND to common power/data ground
  • Connect the SCL pin to the I2C clock SCL pin on your Arduino compatible
  • Connect the SDA pin to the I2C data SDA pin on your Arduino compatible

 

SPI Wiring

Since this is a SPI-capable sensor, we can use hardware or 'software' SPI. To make wiring identical on all microcontrollers, we'll begin with 'software' SPI. The following pins should be used:

  • Connect Vin to the power supply, 3V or 5V is fine. Use the same voltage that the microcontroller logic is based off of
  • Connect GND to common power/data ground
  • Connect the SCK pin to Digital #13 but any pin can be used later
  • Connect the SDO pin to Digital #12 but any pin can be used later
  • Connect the SDI pin to Digital #11 but any pin can be used later
  • Connect the CS pin Digital #10 but any pin can be used later

Later on, once we get it working, we can adjust the library to use hardware SPI if you desire, or change the pins to others.

Install Adafruit_BME680 library

To begin reading sensor data, you will need to install the Adafruit_BME680 library (code on our github repository). It is available from the Arduino library manager so we recommend using that.

From the IDE open up the library manager...

And type in adafruit bme680 to locate the library. Click Install

Load Demo

Open up File->Examples->Adafruit_BME680->bmp680test and upload to your microcontroller wired up to the sensor

Depending on whether you are using I2C or SPI, change the pin names and comment or uncomment the following lines.

#define BME_SCK 13
#define BME_MISO 12
#define BME_MOSI 11
#define BME_CS 10

Adafruit_BME680 bme; // I2C
//Adafruit_BME680 bme(BME_CS); // hardware SPI
//Adafruit_BME680 bme(BME_CS, BME_MOSI, BME_MISO,  BME_SCK);

Once uploaded, open up the serial console at 9600 baud speed to see data being printed out

Temperature is calculated in degrees C, you can convert this to F by using the classic F = C * 9/5 + 32 equation.

Pressure is returned in the SI units of Pascals. 100 Pascals = 1 hPa = 1 millibar. Often times barometric pressure is reported in millibar or inches-mercury. For future reference 1 pascal =0.000295333727 inches of mercury, or 1 inch Hg = 3386.39 Pascal. So if you take the pascal value of say 100734 and divide by 3386.39 you'll get 29.72 inches-Hg.

Humidity is returned in Relative Humidity %

Gas is returned as a resistance value in ohms. This value takes up to 30 minutes to stabilize! Once it stabilizes, you can use that as your baseline reading. Higher concentrations of VOC will make the resistance lower.

You can also calculate Altitude. However, you can only really do a good accurate job of calculating altitude if you know the hPa pressure at sea level for your location and day! The sensor is quite precise but if you do not have the data updated for the current day then it can be difficult to get more accurate than 10 meters.

CircuitPython Wiring & Test

It's easy to use the BME680 sensor with CircuitPython and the Adafruit CircuitPython BME680 module.  This module allows you to easily write Python code that reads the humidity, temperature, pressure, and more from the sensor.

First wire up a BME680 to your board exactly as shown on the previous pages for Arduino.  You can use either I2C or SPI wiring, although it's recommended to use I2C for simplicity.  Here's an example of wiring a Feather M0 to the sensor with I2C:

  • Board 3V to sensor VIN
  • Board GND to sensor GND
  • Board SCL to sensor SCK
  • Board SDA to sensor SDI

And an example of a Feather M0 wired with hardware SPI:

  • Board 3V to sensor VIN
  • Board GND to sensor GND
  • Board SCK to sensor SCK
  • Board MOSI to sensor SDI
  • Board MISO to sensor SDO
  • Board D5 to sensor CS (or use any other free digital I/O pin)

Next you'll need to install the Adafruit CircuitPython BME680 library on your CircuitPython board.  Remember this module is for Adafruit CircuitPython firmware and not MicroPython.org firmware!

First make sure you are running the latest version of Adafruit CircuitPython for your board.

Next you'll need to install the necessary libraries to use the hardware--carefully follow the steps to find and install these libraries from Adafruit's CircuitPython library bundle.  For example the Circuit Playground Express guide has a great page on how to install the library bundle for both express and non-express boards.

Remember for non-express boards like the Trinket M0, Gemma M0, and Feather/Metro M0 basic you'll need to manually install the necessary libraries from the bundle:

  • adafruit_bme680.mpy
  • adafruit_bus_device

You can also download the adafruit_bme680.mpy from its releases page on Github.

Before continuing make sure your board's lib folder or root filesystem has the adafruit_bme680.mpy, and adafruit_bus_device files and folders copied over.

Next connect to the board's serial REPL so you are at the CircuitPython >>> prompt.

Usage

To demonstrate the usage of the sensor we'll initialize it and read the temperature, humidity, and more from the board's Python REPL.

If you're using an I2C connection run the following code to import the necessary modules and initialize the I2C connection with the sensor:

import board
import busio
import adafruit_bme680
i2c = busio.I2C(board.SCL, board.SDA)
sensor = adafruit_bme680.Adafruit_BME680_I2C(i2c)

Remember if you're using a board that doesn't support hardware I2C (like the ESP8266) you need to use the bitbangio module instead:

import board
import bitbangio
import adafruit_bme680
i2c = bitbangio.I2C(board.SCL, board.SDA)
sensor = adafruit_bme680.Adafruit_BME680_I2C(i2c)

Or if you're using a SPI connection run this code instead to setup the SPI connection and sensor:

import board
import busio
import digitalio
import adafruit_bme680
spi = busio.SPI(board.SCK, MOSI=board.MOSI, MISO=board.MISO)
cs = digitalio.DigitalInOut(board.D5)
sensor = adafruit_bme680.Adafruit_BME680_SPI(spi, cs)

Now you're ready to read values from the sensor using any of these properties:

  • temperature - The sensor temperature in degrees Celsius.
  • gas - The resistance (in Ohms) of the gas sensor.  This is proportional to the amount of VOC particles in the air.
  • humidity - The percent humidity as a value from 0 to 100%.
  • pressure - The pressure in hPa.
  • altitude - The altitude in meters.
print('Temperature: {} degrees C'.format(sensor.temperature))
print('Gas: {} ohms'.format(sensor.gas))
print('Humidity: {}%'.format(sensor.humidity))
print('Pressure: {}hPa'.format(sensor.pressure))

For altitude you'll want to set the pressure at sea level for your location to get the most accurate measure (remember these sensors can only infer altitude based on pressure and need a set calibration point).  Look at your local weather report for a pressure at sea level reading and set the seaLevelhPA property:

sensor.seaLevelhPa = 1014.5

Then read the altitude property for a more accurate altitude reading (but remember this altitude will fluctuate based on atmospheric pressure changes!):

print('Altitude: {} meters'.format(sensor.altitude))

That's all there is to using the BME680 sensor with CircuitPython!

Here's a complete example that prints all the sensor's values once a second.  Save this as a main.py on your board (note it assumes a hardware I2C connection to the sensor):

import board
import busio
import time

import adafruit_bme680


# Initialize I2C bus and create sensor instance.
i2c = busio.I2C(board.SCL, board.SDA)
sensor = adafruit_bme680.Adafruit_BME680_I2C(i2c)

# Main loop prints sensor values every second.
while True:
    print('Temperature: {} degrees C'.format(sensor.temperature))
    print('Gas: {} ohms'.format(sensor.gas))
    print('Humidity: {}%'.format(sensor.humidity))
    print('Pressure: {}hPa'.format(sensor.pressure))
    time.sleep(1.0)

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