This example implements the Heart Rate service and Pulse Oximeter service service. It enables a peer device to connect and receive heart rate and pulse Oximeter values via Bluetooth. The reported values are measured by a bio-sensor located on the Heart Rate 2 Click.
This code example has a related code example, which may be worth reading before. Find it here:
- GSDK v4.4.0
The Heart Rate 2 Click board can just be "clicked" into its place. Be sure that the board's 45-degree corner matches the Explorer Kit's 45-degree white line. The board also has I2C-bus pull-ups. Just be sure that the click board is configured into I2C-mode (the default) by the resistors and not into SPI-mode. Afterwards, power up the board by connecting the kit to a PC using a microUSB cable. The Power LED on Heart Rate 2 Click board will light when the kit is powered.
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.
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From the Launcher Home, add your hardware to My Products, click on it, and click on the EXAMPLE PROJECTS & DEMOS tab. Find the example project with the filter "bio-sensor".
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Click Create button on both Bluetooth - Explorer Kit I2C Bio Sensor examples. Example project creation dialog pops up -> click Create and Finish and Project should be generated.
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Build and flash this example to the board.
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Create a Bluetooth - SoC Empty project for your hardware using Simplicity Studio 5.
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Copy the app.c file and the hrm folder into the project's root folder (app.c will replace the existing file).
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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.
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Install the software components:
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Open the .slcp file in the project.
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Select the SOFTWARE COMPONENTS tab.
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Install the following components:
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Install the I2CSPM component with the default instance name: mikroe.
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Install the first Simple Button component with the default instance name: btn0.
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Install IO Stream: USART component with the default instance name: vcom.
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Install the Log component (found under [Application] > [Utility] group).
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- Build and flash this example to the board.
Note:
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Make sure that the bluetooth_applications repository is added to Preferences > Simplicity Studio > External Repos.
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Do not forget to flash a bootloader to your board, see Bootloader for more information.
Below is an overview of the HRM/SpO2 software architecture.
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.
The GATT changes were adding a new Heart Rate service and Pulse Oximeter Service service. The Heart Rate service uses the UUID 0x180D that has a Heart Rate Measurement characteristic with the Notify property. The Pulse Oximeter Service service uses the UUID 0x1822 that has a PLX Continuous Measurement characteristic with the Notify property. As they are the Bluetooth SIG Assigned UUID, most applications know how to display the value correctly.
When the connection is opened and the notification is enabled, a 500 milliseconds periodic timer is started. When the timer is triggered, the client is notified about the updated values. The sl_bt_evt_gatt_server_characteristic_status_id-event is handling the notification enable/disable control. If the connection is closed, the periodic timer will be stopped, too.
BTN0 button is used to start/stop the measurement. Upon reset, press the BTN0 button to start the HRM/SpO2 measurement. Users should put their finger on the sensor with a proper pressure (solid contact between the finger and the sensor without optical leakage and don’t press with force) and stay idle for at least 10 seconds. Once started, the measurement can be stopped at anytime by pressing the BTN0 button again.
Maxm86161 includes an optical proximity function which could significantly reduce energy consumption and extend the battery life when the sensor is not in contact with the skin. There is a compiler option PROXIMITY in the build configuration of the project that can choose Green/IR/Red LED for this feature.
The Silicon Labs EFR Connect application utilizes the Bluetooth adapter on your phone/tablet to scan, connect and interact with BLE devices. To run this example, an iOS or Android smartphone with EFR Connect app installed is required.
Open the EFR Connect application on your smartphone and allow the permission request when opened for the first time. Click [Develop] -> [Browser] and you will see a list of nearby devices which are sending Bluetooth advertisements. Find the one named "Silabs HRM Example" and click the connect button on the right side.
Wait for the connection to establish and GATT database to be loaded, then find the Heart Rate service or the Pulse Oximeter Service service, and click More Info.
To check the heart rate value and the status of finger (ON/OFF), users need turn on notify in the Heart Rate Measurement characteristic of the Heart Rate service. To check both the heart rate and the SpO2 values, users need turn on notify in the PLX Continuous Measurement characteristic of the Pulse Oximeter Service service.
The demo firmware includes a debug mode that enables HRM/SpO2 data including raw samples from the sensor to be streamed to a host PC via the Wireless STK’s USB interface. There is a compiler option UART_DEBUG in the build configuration of the project. There are 4 levels to choose from. If the UART_DEBUG is set to level 0, the USB debug mode will be disabled. Level 1 shows only raw PPG value, level 2 shows only the Heart Rate and SpO2 values and level 3 shows both raw PPG value, the Heart Rate and SpO2 values.
Users can launch the Console that is integrated on Simplicity Studio or can use a third-party terminal tool like TeraTerm to receive the data from the USB. A screenshot of the console output is shown in the figure below.
The raw data in each column represents "green LED, IR LED, red LED”. Heart rate and SpO2 values are updated once a second. The user can easily log the raw samples and debug messages to a *.csv file for post-analysis.
- The HRM/SpO2 algorithm is developed by Silicon Labs for evaluation purpose. The performance of the algorithm is as it is. We do NOT plan to improve the performance or support any performance-related issues.