SparkFun gator:environment Hookup Guide

Introduction

Do you have an experiment involving environmental changes?

SparkFun gator:environment - micro:bit Accessory Board

SEN-15269

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The gator:environment is the solution for any environmental experimentation. It utilizes both the CCS811 and BME280 ICs for all of your climate and atmospheric quality readings. The CCS811 is an exceedingly popular sensor, providing readings for equivalent CO₂ (or eCO₂) in the parts per million (PPM) and equivalent total volatile organic compounds (or eTVOC) in the parts per billion (PPB). While, the BME280 provides a combined humidity, temperature, and barometric pressure readings. This tutorial will show you how to get started using this environmental sensor with the gator:bit (v2) in the micro:bit development environment.

Required Materials

To get started, you'll need a micro:bit to control everything. Each of the products below includes a micro:bit, but the kit and bundle also include some additional accessories that you may want as well.

micro:bit Board

DEV-14208

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micro:bit Go Bundle

DEV-14336

18 Retired

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SparkFun Inventor's Kit for micro:bit

KIT-15228

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To easily use the gator board ecosystem, a gator:bit (v2) will help breakout the necessary pins and you will also need alligator and/or banana cables to connect the gator:bit to the gator:environment.

Alligator Test Leads - Multicolored (10 Pack)

PRT-12978

$3.50

4

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Banana to Banana Cable - Right Angle

CAB-15368

$4.95 $4.46

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Favorited Favorite 5

SparkFun gator:bit v2.0 - micro:bit Carrier Board

DEV-15162

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(*These banana cables have a special diameter on the attachment points designed specifically for use with the micro:bit ecosystem. They may or may not be compatible with the banana cables used on your test equipment.)

You may already have some of these materials, so feel free to modify your cart as necessary.

Logic Levels

Learn the difference between 3.3V and 5V devices and logic levels.

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I2C

An introduction to I2C, one of the main embedded communications protocols in use today.

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micro:climate Kit Experiment Guide

A weather station kit that is built on top of the inexpensive, easy-to-use micro:bit and Microsoft MakeCode.

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CCS811/BME280 (Qwiic) Environmental Combo Breakout Hookup Guide

Sense various environmental conditions such as temperature, humidity, barometric pressure, eCO2 and tVOCs with the CCS811 and BME280 combo breakout board.

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If you aren't familiar with the micro:bit, we recommend reading here for an overview.

micro:bit Ecosystem

We would also recommend taking a look at the following tutorials if you aren't familiar with them.

Getting Started with the micro:bit

The BBC micro:bit is a compact, powerful programming tool that requires no software installation. Read on to learn how to use it YOUR way!

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Getting Started with MicroPython and the SparkFun Inventor's Kit for micro:bit

Learn MicroPython with the micro:bit.

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How to Load MicroPython on a Microcontroller Board

This tutorial will show you how to load the MicroPython interpreter onto a variety of development boards.

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SparkFun gator:bit v2 Hookup Guide

The gator:bit v2 is a breakout board for the BBC micro:bit. The gator:bit exposes almost every pin on the micro:bit to clippable pad with circuit protection. It also has as built-in addressable LEDs and a built-in buzzer.

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Hardware Overview

The gator:environment consists of 4 pads for power and data.

Contacts	Direction	Description
GND	N/A	Ground: Reference voltage and ground loop.
3.3V	In	Power: Provides 3.3V to board.
SDA	Bi-directional	Data: Data and commands are transmitted between the sensor and microcontroller.
SCL	In	Clock: The microcontroller provides the timing needed to communicate on the data line.

Power

The specified operating voltage for the BME280 is between 1.71V - 3.6V and 1.8V - 3.6V for the CCS811. For use with the gator:bit (v2) and micro:bit, you should provide 3.3V through the 3V3 and GND pads to keep the logic levels consistent; the 3.3V input is then regulated to 3.1V for the sensors.

Power connection pads and power indication LED.

On average, both sensors will consume about 5 mA of current, with a maximum of 13 mA.

BM280

The BME280 is a combined digital humidity, pressure, and temperature sensor that communicates over an I²C bus. For the most part, users will only need to know I²C addresses to prevent address conflicts with other devices or sensors.

BME280 combined humidity, pressure, and temperature sensor.

Here are some of the characteristics of the BME280 sensor from the datasheet:

Characteristic	Range
Operating Voltage	1.71V to 3.6V
Supply Current	< 714 µA
Humidity	Range: 0 to 100% RH Resolution: .008% RH Absolute Accuracy Tolerance: ±3% from 20 - 80%
Temperature	Range: -40°C to 85°C Absolute Accuracy: ±(0.5 - 1.25) °C Resolution: 0.01 °C
Pressure	Range: 300 to 1100 hPa (30,000 - 110,000 Pa or approx. 4.35 - 15.95 Psi) Absolute Accuracy: ±(1 - 1.7) hPa Relative Accuracy: ±0.12 hPa Maximum Resolution: 0.18 Pa
I²C Address	0x77 (HEX)

What is Humidity?

Humidity is a measurement of the amount of water vapor in the air. A simple demonstration of humidity is when you breathe on a cold piece of glass, the water vapor from your breath condenses into beads of liquid water. The humidity measurement from the BME280 is reported in terms of relative humidity. Humidity is often associated with various topics in science. For example:

Humidity affects your body's ability to regulate temperature through perspiration.
In civil engineering, humidity affects how concrete cures and contributes to the overall strength.
In various climates, humidity can factor into conditions like precipitation or fog for meteorological reports.

What is Temperature?

Temperature for the most part is the quantification of how hot or cold something is. The BME280 measures the ambient temperature (or temperature of the relative environment). Temperature is reported in different scales or units, the BME280 measures temperature in degrees Celsius. Temperature is an essential unit of measurement that affects all aspects of physical science¹. Some applications of the BME280 for temperature are:

Measurements of the ambient temperature for weather meters.
Replicating the original Joule experiment for measuring a calorie (waterproofing required).
Measuring solar radiation as used by solar water heaters.

1. Note: Sometimes the thermal affects on a system are negligible and therefore, ignored to simplify the model or experiment.↩

What is Pressure?

The BME280 measures pressure, specifically atmospheric or barometric pressure. Pressure is usually described as the perpendicular force applied to the surface of an object per unit area; in fluid mechanics, it is also referred to as the compressive stress at a particular point. The BME280 reports pressure units in Pascals. Pressure measurements are useful in a variety of applications:

Experiments relating to the Ideal Gas Law or related principles.
Altimeter: Used to determine (pressure) altitude of above a fixed level, which is based on the Barometric formula.
Atmospheric pressure has a direct relation to wind and local weather.

CCS811

The CCS811 is a digital metal oxide (MOX) gas sensor that detects wide range of Volatile Organic Compounds (VOCs). With an integrated microcontroller that implements special algorithms to process the raw measurements, the CCS811 outputs the equivalent total VOC (eTVOC) and equivalent CO₂ (eCO₂) values over an I²C connection. For the most part users will only need to know I²C addresses to prevent address conflicts with other devices or sensors.

CCS811 metal oxide sensor.

Here are some of the characteristics of the CCS811 sensor from the datasheet:

Characteristic	Range
Operating Voltage	1.8V to 3.6V
Operational Environment	Temperature: -5 to 50°C Humidity: 10 to 95% RH
Supply Current	30 mA (average)
Equivalent Total VOCs (eTVOC)	0 - 32768 ppb (parts per billion)
Equivalent CO₂ (eCO₂)	400 - 29206 ppm (parts per million)
I²C Address	0x5B (HEX)

Functionality Notes:

The CCS811 implements a highly reliable micro-hotplate for the gas sensor. However, the performance in terms of resistance levels and sensitivities varies in the early stages. Therefore, AMS recommends that you run (or burn-in) this sensor for 48 hours on your first use. After the burn-in conditioning, a run-in period is required after long idle periods. The run-in time for the CCS811 is 20 minutes, before sensor stabilizes and accurate readings are generated.
(*Essentially, run the board by taking readings for 48 hours the first time you use it to burn-in the sensor. Additionally, after extended periods between uses, you may also need to run the sensor for 20 minutes to stabilize the outputs due to the run-in period.)
To help with the sensor accuracy, the BME280 is also used to provide temperature and humidity compensation. Therefore, any discrepancies between the BME280 readings and the conditions of the ambient air will produce imprecise results. A good example of this is if the board is heated above the temperature of the ambient air; the heating would offset the BME280 and result in inaccurate measurements.
A baseline correction it is maintained on-the-fly in software, which is enabled automatically after initial device operation. There is the capability for manual correction, but it has not been implemented to simplify the sensor operation.

Equivalent TVOC: What are Volatile Organic Compounds?

MOX sensors are a great method for volatile organic compound (VOC) detection. VOCs are organic chemicals, usually with a high vapor pressure or high volatity, due to their low boiling point at room temperature. For indoor air quality (IAQ), these compounds are often attributed to health effects from mild irritation in brief exposures to more serious health risks with compounding long-term exposure.

Here is a list of VOCs detected by the CCS811:

Alcohols
Aldehydes
Ketones
Organic Acids
Amines
Aliphatic and Aromatic Hydrocarbons

For more information about VOC and their effects on IAQ, check out these resources.

Here are some ideas for experiments involving VOCs:

TeachEngineering: I've Gotta Get Some Air
- Sensing Air Pollution (Safety: adult supervision and open air environment required)
VOC emission experiments in nature and lab

Note: Unfortunately, the standards associating specific chemical compounds and their health effects are wide and varied. Additionally, the number of VOCs are so numerous that it is impossible for a single sensor to detect each compound. Most sensors, like the CCS811, target specific VOCs and then use algorithms to estimate an equivalent total volatile organic compound (eTVOC) values. This sensor is valuable in providing information for the presence of contaminants in indoor air, but it is trend data and not recommended for exact measurements of VOCs.

[Source- Guidelines for CO₂ Sensor Selection]

Equivalent CO₂: What is Carbon Dioxide?

Carbon Dioxide (CO₂) is a trace gas in Earth's atmosphere and it is a naturally occurring due to its solubility and dissolution in water. CO₂ is also a common byproduct of combustion, aerobic, and decomposition reactions. It is highly versatile and extensively used in multiple industrial applications.

A common topic about CO₂ is its growing abundance in Earth's atmosphere and the affect that has on climate change, as a greenhouse gas. The Scripps Institution of Oceanography at UC San Diego, has maintained continuous measurements of the accumulation of atmospheric carbon dioxide since 1958. A graph based on those measurements, taken from the Mauna Loa Observatory in Hawaii, is referred to as the Kneeling curve (named after Charles David Keeling).

Kneeling Curve: The bright red line shows the monthly average or carbon dioxide in parts per million (ppm). The dark red line shows the annual trend, calculated as a 12-month rolling average. [Source: Climate.gov]

Here are resources to some simple experiments involving carbon dioxide:

For more information on carbon dioxide concentration levels in the atmosphere, check out these resources:

Note: Unfortunately, CO₂ isn't a VOC and MOX type of sensors can't directly measure CO₂, despite being great at VOC detection. However, in an indoor setting, humans are a primary source of VOCs through the process of breathing. The equivalent CO₂ (eCO₂) values are then estimated based on algorithms that are used to analyze the sensor data to determine the TVOC attributed by the presence of humans. This type of sensor should not be used in applications that directly requires the measurement of CO₂; it is an inferred value.

[Source- Guidelines for CO₂ Sensor Selection]

I²C Connection

I²C is a communication protocol used to transfer data between master and slave devices. It is a 2-wire connection consisting of SDA (data) and SCL (clock). The protocol is pretty well defined so it can be shared with multiple devices. This is beneficial for daisy chaining multiple devices together on a single bus. The primary thing users will need to watch out for is address conflicts (you can't have devices with the same address).

I²C connection pads.

Hardware Assembly

Connecting your gator:environment to the gator:bit (v2) is simple. The board can also be daisy-chained with other I²C boards. This can easily be done with alligator cables or these special banana cables.

Hardware assembly of connections used in example. Click to enlarge.

Example of daisy chaining multiple I²C gator boards. Click to enlarge.

gator:environment	GND	3V3	SDA	SCL
gator:bit (v2)	GND	3.3V OUT	P20 (SDA)	P19 (SCL)

Adding the MakeCode Extension

Note: This tutorial assumes you are familiar with MakeCode, the gato:bit (v2), and the micro:bit board.

If you have not previously used MakeCode, please check out the Quick Start Guide fro micro:bit.
If this is your first time using a micro:bit, please review our Getting Started with the micro:bit guide.
If this is your first time using the gato:bit (v2), please review our SparkFun gator:bit v2 Hookup Guide.

The easiest way to get started using the gator:environment is to use Microsoft MakeCode, a web-based block editor. This tutorial assumes you are familiar with the with MakeCode, the gato:bit (v2), and the micro:bit development board. If this is your first time check out this guides linked in the suggested reading section (above).

Installing Extensions

To get started with using MakeCode with the miccro:bit, head over to the MakeCode for micro:bit website by Microsoft. Then, click the New Project button to start a new project and open the Editor. (*Yes, all you only need to get start coding is a computer with internet access, an up-to-date web browser, and an available USB port!)

Click the New Project button to start a new project and open the Editor. Click on image to enlarge.

Once you have the editor up, click on the the Advanced block in the block library to reveal the drop down menu.

Click on the the Advanced block in the block library to reveal the drop down menu. Click on image to enlarge.

Finally, click on the Extensions block. This should bring up the extensions page. (*Alternatively, you could also click on the extensions link from the settings menu.)

Click on the the Extensions block to open the extensions page. Click on image to enlarge.

There are two methods for finding the gator:environment extension:

Search for the name used on the extension³.
Use the link to the GitHub repository for the pxt-package as the search term.

Use the search bar to find the extension you want to install. Click on image to enlarge.

Note: Unfortunately, it does take time to get an extension approved by the micro:bit Educational Foundation before it can be searchable by name. Part of the requirements for the approval process involves a live product page. Therefore, at the time of the launch of this product, the extension has not been approved yet and the only method of adding the extension is to use the link to the GitHub repository of the pxt-package. We will update this tutorial as soon as the extension has been approved.↩

Search for the PXT-Package

Search for the gator:environment extension using the GitHub repository link to the pxt-package:

https://github.com/sparkfun/pxt-gator-environment

Search for Extension. Then, click on the box to add it to the block library. Click on image to enlarge.

Then, click on the box for the extension to add it to the block library. The gator:environment extension should now appear in the block library.

Extension in the block library; click on the block to open menu options. Click on image to enlarge.

To verify that you have added the extension, click on the gator:environment block to make sure that your drop down menu options match the image below.

Available blocks for the gator:environment extension. Click on image to enlarge.

MakeCode Examples

Now that you have added the gator:environment extension to the Editor, lets start with some example code. Plug the micro:bit into your computer using an USB micro-B cable after you have assembled your hardware with the instructions from the previous section. The micro:bit should appear on your computer as a removable storage device.

The micro:bit showing up as a USB drive on a Windows computer. Click to enlarge.

To upload new code, this is where you will be copying the downloaded .hex file to later.

Block Functions

initialize gator:environment sensor
This block should be pretty self explanatory, it sets the sensor up to be used. You should use this within the on start block.

_____ value
This is a value block as indicated by the block's shape. There is a drop down menu with selectable options for the output value of the block. Below is a description of the available menu options:

degreeC- Reports temperature reading from BME280 in Celsius (°C).
degreeF- Reports temperature reading from BME280 in Fahrenheit (°F).
humidity- Reports humidity reading from BME280 in relative humidity (RH%).
pressure- Reports pressure reading from BME280 in Pascals (Pa).
eCO2- Reports equivalent CO₂ reading from CCS811 in parts per million (ppm).
TVOC- Reports equivalent TVOC reading from CCS811 in parts per billion (ppb).

Basic Read

Below, is a simple example of how to take simple measurements from the sensor. To use this example, there are multiple options for accessing the .hex file:

Replicate the block functions from the display below to copy the example project. Then download the .hex file.
Expand the display widow to pull up the example project. Then download the .hex file.
Use this link to pull up the example project. Then download the .hex file.
Download the .hex file from the button below or the link on the bottom of the display.

Download .hex File for Example

The output is redirected over the serial port to avoid conflicts on pins P0 and P1, which are also used for serial communication. To read the sensor values, pull up your favorite serial terminal emulator. Then, connect to the serial port that the micro:bit is on; the default baud rate is 115200 bps. Below, is an example of the sensor output for the example code.

Example of readings from the sensor.

Troubleshooting the Extension

Extension not working?

This product's extension has a dependency on Microsoft's build process. If the usual method of installing the MakeCode extension gives an error, you will need to manually install the MakeCode extension. We have provided a local build of this extension that can be uploaded to MakeCode:

gator:environment extension

To manually install this extension in makecode, go to the "Extensions" tab on the left side of the makecode site:

In the location you'd normally search for an extension, you'll notice an upload button on the right:

Click on this, and you'll get a window allowing you to upload your own built extension. Navigate to where you saved the above extension hex, and upload it to your project.

You should be able to see the extension and its functions now. In addition, you'll be able to build and download your project to your variant of micro:bit.

Other Troubleshooting Tips

Here are a few tips for troubleshooting this device.

Sensor Heating

The CCS811 is a MOX sensor that uses a hotplate to detect the VOCs. Additionally, the CCS811 relies on the BME280 for ambient air temperature and humidity to compensate the MOX readings. The heat generated from the CCS811 should be isolated from the BME280 to prevent the heat from affecting the BME280 and thus affecting the compensation values. However, this doesn't take into account any external heating which would also affect the temperature and humidity for compensation of the CCS811.

Equivalent CO₂ and TVOC

As mentioned in the Hardware Overview section, the CO₂ and TVOC values are equivalent; they are interpreted values. If you are trying to measure CO₂ directly, the CCS811 sensor will not be able to detect it. Additionally, the CCS811 only measures specific VOCs.