SparkFun Environmental Sensor Breakout - BME68x (Qwiic) Hookup Guide

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Contributors: El Duderino, santaimpersonator
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Troubleshooting

In this section we'll cover a few tips and tricks for troubleshooting common questions with the Environmental Sensor Breakout - BME68x.

Using the BME68x

At first sensor usage, minimum 48 hours of "burn in" should be made. Later, at each usage, 30 min. of functioning should passed before sensor data may be considered as valid. (*In their video for the BME688 evaluation board, Bosch recommends at least 24 hrs. to stabilize the sensors.)

In order to avoid contamination of its gas scanning capabilities, DO NOT touch the metallic casing of the BME688 sensor. Unfortunately, at this time, there are no recommendations or instructions for decontaminating the sensor once it has been touched.

Gas Readings Interpretation

The library used in this tutorial only prints out the raw resistance values from the gas sensor on the BME680. You can use these values as a rough estimate of air quality where lower resistance values equate to a higher concentration of gases measured (and vice versa). If you want to get true Indoor Air Quality (IAQ) measurements from the BME680, we recommend taking a look at Bosch's BSEC Arduino Library which includes an algorithm to convert the resistance value to an IAQ value. For more information, refer to that library as well as sections 1.2 and 4.2 in the BME680 Datasheet. Calculated IAQ measurements are beyond the scope of this tutorial.

BME688 AI and Gas Scanning Features

In order to avoid contamination of its gas scanning capabilities, DO NOT touch the metallic casing of the BME688 sensor. Unfortunately, at this time, there are no recommendations or instructions for decontaminating the sensor once it has been touched.

At first sensor usage, minimum 48 hours of "burn in" should be made. Later, at each usage, 30 min. of functioning should passed before sensor data may be considered as valid. (*In their video for the BME688 evaluation board, Bosch recommends at least 24 hrs. to stabilize the sensors.)

IAQ (Air quality index), target gas scanner selectivity, VOC, VSC data and other BME688 features may be accessed using the Bosch Sensortec Arduino libraries:

The BME AI-Studio is only available for Win and Mac OS computers and the accompanying Bluetooth app is only available for Android phones. *For more information on the available software, please refer to the Bosch's BME688 software page.

*For more information on these features, users can also reference the FAQ page for the BME688 on Bosch's forum.

Incorrect Temperature Data

You may notice some deviation from the true ambient temperature in your data as residual heat from the hot plate for the gas sensor in the BME68x0 can cause minor fluctuations in the observed temperature. The heating phase starts after temperature, pressure and humidity measurements are complete so there should be no heating during those measurements but subsequent readings may be skewed. The IIR filters can help here but if needed, you can compensate for this by measuring the average deviation and subtracting that from your temperature data.

Incorrect Altitude Data

The altitude data is collected by converting the barometric pressure. This is a great tool for approximate altitude readings but things like weather patterns can affect the accuracy of the altitude. The examples use the standard measurement for pressure at sea level (1013.25 hPa) in the calculation so you may wish to adjust that with a corrected value for a more accurate altitude data. Refer to this Wikipedia page and this section of our MPL3115 Pressure Sensor Hookup Guide for more information.

Chip Select Definition

As we covered in the previous section, if you choose to communicate with the BME68x via SPI, make sure you are connecting to the correct pins on your development board (COPI, CIPO, SCK and CS) as well as modifying the Chip Select definition to the appropriate I/O pin used for CS on your controller. If you are not certain which pin is used for CS, refer to documentation for your particular development board.

BME688 SPI Jumpers: In order to communicate with the BME688 Qwiic board over SPI, users will need to cut the CSB and ADR (leave floating) jumpers. *See the CSB Jumper section in the Hardware Overview page, for more information.
Note: You may not recognize the COPI/CIPO labels for SPI pins. SparkFun has joined with other members of OSHWA in a resolution to move away from using "Master" and "Slave" to describe signals between the controller and the peripheral. Check out this page for more on our reasoning behind this change. You can also see OSHWA's resolution here.

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