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README.md

Bluetooth - Air Quality Monitor

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Overview

This project aims to implement an air quality monitor and notification system using Silicon Labs development kits and external sensors integrated with the BLE wireless stack. The block diagram of this application is shown in the image below:

system overview

More detailed information can be found in the section How it works.

This code example referred to the following code examples. More detailed information can be found here:

Table Of Contents

SDK version

Software Required

Hardware Required

Connections Required

The hardware connection is shown in the image below:

hardware connection

Setup

To test this application, you can either create a project based on an example project or start with a "Bluetooth - SoC Empty" project based on your hardware. You should connect your board to the PC using a MicroUSB cable.

Note

Based on an example project

  1. From the Launcher Home, add your board to My Products, click on it, and click on the EXAMPLE PROJECTS & DEMOS tab. Find the example project filtering by 'air quality'.

    create_demo

  2. Click Create button on the Bluetooth - Air Quality Monitor example. Example project creation dialog pops up -> click Create and Finish and Project should be generated.

  3. Build and flash this example to the board.

Start with a "Bluetooth - SoC Empty" project

  1. Create a Bluetooth - SoC Empty project for your hardware using Simplicity Studio 5.

  2. Copy all the header files and source files in the 'inc' and 'src' folders to the root folder of the project (overwriting the existing files).

  3. Open the .slcp file. Select the SOFTWARE COMPONENTS tab and install the software components:

    • [Services] → [IO Stream] → [IO Stream: USART] → vcom
    • [Application] → [Utility] → [Log]
    • [Application] → [Utility] → [Timer]
    • [Platform] → [Driver] → [I2C] → [I2CSPM] → qwiic
    • [Platform] → [Driver] → [PWM] → [PWM] → mikroe
    • [Platform] → [Driver] → [Button] → [Simple Button] → btn0
    • [Third Party Hardware Drivers] → [Sensors] → CCS811 - [Air Quality Sensor (Sparkfun)]
    • [Third Party Hardware Drivers] → [Audio & Voice] → [CMT_8540S_SMT - Buzz 2 Click (Mikroe)]
    • [Third Party Hardware Drivers] → [Display & LED] → [SSD1306 - Micro OLED Breakout (Sparkfun) - I2C]
    • [Third Party Hardware Drivers] → [Services] → [GLIB - OLED Graphics Library]
    • [Bluetooth] → [OTA] → [In-Place OTA DFU] → uninstall
    • [Platform] → [Bootloader Application Interface] → uninstall.

  4. Import the GATT configuration:

    • Open the .slcp file in the project again.
    • Select the CONFIGURATION TOOLS tab and open the "Bluetooth GATT Configurator".
    • Find the Import button and import the gatt_configuration.btconf file.
    • Save the GATT configuration (ctrl-s).

  5. Build and flash this project to the board.

How it Works

Application Overview

app overview

GATT Database

The application is based on the Bluetooth - SoC Empty example. Since the example already has the Bluetooth GATT server, advertising, and connection mechanisms, only minor changes are required.

  • BLE advertiser name: Air Quality
  • [Service] Air Quality - UUID: 3a79c933-c922-45c7-b5e7-9bdefd126dd9
    • [Char] Alarm Enabled - UUID: ec26adea-75af-409d-b267-51a4e753e9ea
      • [Read] - Get alarm enabled
      • [Write] - Set alarm enabled (1 - enable, 0 - disable)
    • [Char] Buzzer Volume - UUID: c5fd8492-9c55-4c18-b761-99b8cf9bca77
      • [Read] - Get configured buzzer volume
      • [Write] - Set buzzer volume (0 - 10)
    • [Char] Measurement Interval - UUID: 98205b49-a9e1-4bfc-a18d-60d36798397f
      • [Read] - Get configured measurement interval in s
      • [Write] - Set configured measurement interval in s (1 - 30)
    • [Char] CO2 Threshold - UUID: 0af3e688-a5a8-435d-bf6a-0f2443428993
      • [Read] - Get CO2 Threshold (ppm)
      • [Write] - Set CO2 Threshold (ppm)
    • [Char] tVOC Threshold - UUID: aad57e11-edb0-4a0c-8590-aad8adbbd23d
      • [Read] - Get tVOC Threshold (ppb)
      • [Write] - Set tVOC Threshold (ppb)
    • [Char] CO2 - UUID: c099dd9-7887-4ca6-a169-92a5e9ed7926
      • [Read] - Get the latest measured CO2 level (ppm)
      • [Notify] - Get the latest measured CO2 level (ppm) automatically
    • [Char] tVOC - UUID: d07aeadd-1633-48ae-a114-800cfdaa0d79
      • [Read] - Get the latest measured tVOC level (ppb)
      • [Notify] - Get the latest measured tVOC level (ppb) automatically
    • [Char] Alarm Status - UUID: d07aeadd-1633-48ae-a114-800cfdaa0d79
      • [Read] - Get the latest Alarm Status
      • [Notify] - Get the latest Alarm Status automatically
    • [Char] Air Quality Index - UUID: ca19fb61-b04b-409a-8a18-c37560bdf05a
      • [Read] - Get the latest Air Quality Index
      • [Notify] - Get the latest Air Quality Index automatically

Air Quality Monitor Implementation

The Initialization software flow is as follows:

Flow diagram

  1. First, the software initializes the peripherals, the Bluetooth stack, and logging to the virtual COM port.

  2. After the sl_bt_evt_system_boot_id event arrives, it sets up the security manager to bond with an iOS/Android device. Then, it starts advertising.

  3. Every time the timer expires, an Air quality monitor event handler retrieves and processes the measured air quality data as described below:

    Flow diagram

  4. When the BTN0 button is pressed, the software checks the notification feature status, and buzzer state by the flowchart below:

    Flow diagram

OLED Display

Measured values are displayed on the OLED display:

More detailed information can be found in the section Testing.

Testing

Upon reset, the application will display the Silicon Labs logo on the OLED screen for a few seconds. Then you can check the measured CO2 and tVOC values on the OLED screen. You should expect a similar output to the one below.

OLED display

Note

The measured CO2 and tVOC values will be more accurate after the sensor is warmed up.

Follow the below steps to test the example with the Simplicity Connect app:

  1. Open the Simplicity Connect app on your smartphone and allow the permission requested the first time it is opened.

  2. Find your device in the Bluetooth Browser, advertising as Air Quality, and tap Connect. Accept the pairing request if prompted.

    pair request

  3. Navigate to the Unknown Services in the GATT database.

  4. Try to read, write, re-read the characteristics, and check the value.

  5. You can launch the Console that is integrated into Simplicity Studio or can use a third-party terminal tool like Tera Term to receive the data from the virtual COM port. Use the following UART settings: baud rate 115200, 8N1, no flow control. You should expect a similar output to the one below.

    logs

Tip

The application handles characteristic values as hexadecimal numbers in Little Endian format. So, to write a 2-byte attribute—for example, to configure the setpoint parameter to 300 (representing 30 °C)—the value 2C01 should be entered in the HEX field.

Report Bugs & Get Support

To report bugs in the Application Examples projects, please create a new "Issue" in the "Issues" section of bluetooth_applications repo. Please reference the board, project, and source files associated with the bug, and reference line numbers. If you are proposing a fix, also include information on the proposed fix. Since these examples are provided as-is, there is no guarantee that these examples will be updated to fix these issues.

Questions and comments related to these examples should be made by creating a new "Issue" in the "Issues" section of bluetooth_applications repo.