bluetooth_controlling_led_from_smartphone

Bluetooth - Controlling LED from Smartphone

Description

This example is an effective way to become familiar with the Silicon Labs Bluetooth stack and a Wireless Development Kit. The example shows how to develop a simple software to control the Wireless Development Kit's LEDs with a mobile phone application.

There are 3 main tasks, as follows:

• Editing the GATT Database.
• Controlling the LED on the board using Simple LED driver.
• Reacting on Bluetooth events, when a remote device reads/writes the GATT database.

Editing the GATT Database

Editing the GATT database of the Bluetooth device is made easy with Silicon Labs Bluetooth SDK using the GATT Configurator as an easy-to-use graphical tool. This example shows how to add a standard characteristic, adopted by the Bluetooth SIG, to the database, the so-called Digital characteristic.

To see the format and requirements of adopted characteristics, see the list here.

The Digital characteristic is designed to control and poll the state of digital I/Os. See the Setup section to learn how to add this characteristic to your database.

Controlling the LED

This application uses the Simple LED driver, which is integrated into Silicon Labs Bluetooth SDK. It provides very simple API functions to initialize, control on/off, and read the state of the LEDs:

// initialize simple LED
sl_led_init(&sl_led_led0);
 
// turn on LED, turn off LED, and toggle
sl_led_turn_on(&sl_led_led0);
sl_led_turn_off(&sl_led_led0);
sl_led_toggle(&sl_led_led0);
 
// get the state of the led
sl_led_state_t state = sl_led_get_state(&sl_led_led0);

The Setup section will show how to add the driver to the project by installing in the Software Components.

Note that when the Simple LED driver is installed, the function sl_led_init is automatically added in sl_system_init function.

Reacting to Bluetooth Events

When the mobile app performs a read or write on the Digital characteristic, it triggers sl_bt_evt_gatt_server_user_write_request or sl_bt_evt_gatt_server_user_read_request events and we can handle them in our application.

The code below processes the event sl_bt_evt_gatt_server_user_write_request: receive the state, control the LED then send the response to the client.

case sl_bt_evt_gatt_server_user_write_request_id:
  // Automation IO digital control
  if (evt->data.evt_gatt_server_user_write_request.characteristic
      == gattdb_led_control) {
    // Write user supplied value to LEDs.
    // Both HEX and ASCII formats are supported to control the LED.
    if ((evt->data.evt_gatt_server_attribute_value.value.data[0] == 1)
        || (evt->data.evt_gatt_server_attribute_value.value.data[0] == 0x31)) {
      app_log("Turn on led\n");
      sl_led_turn_on(&sl_led_led0);
    } else if ((evt->data.evt_gatt_server_attribute_value.value.data[0] == 0)
        || (evt->data.evt_gatt_server_attribute_value.value.data[0] == 0x30)){
      app_log("Turn off led\n");
      sl_led_turn_off(&sl_led_led0);
    } else {
      app_log("Invalid attribute value\n");
    }
    sc = sl_bt_gatt_server_send_user_write_response(
      evt->data.evt_gatt_server_user_write_request.connection,
      gattdb_led_control,
      SL_STATUS_OK);
    app_assert_status(sc);
  }
  break;

The code below processes the event sl_bt_evt_gatt_server_user_read_request: read the LEDs statuses and sends the status byte to the client in response.

case sl_bt_evt_gatt_server_user_read_request_id:
  // Automation IO digital control
  if (evt->data.evt_gatt_server_user_read_request.characteristic
      == gattdb_led0) {
    app_log("read led 0 \n");
    led_status = sl_led_get_state(&sl_led_led0);
    sc = sl_bt_gatt_server_send_user_read_response(
      evt->data.evt_gatt_server_user_read_request.connection,
      gattdb_led0,
      SL_STATUS_OK,
      1,
      &led_status,
      &sent_len);
    app_assert_status(sc);
  }
  break;

All of the above is implemented in the attached app.c file. After setting up the GATT database as described in the previous section, replace the default app.c with the attached one for a quicker example setup.

Gecko SDK version

• GSDK v4.4.0

Hardware Required

• A Silicon Labs compatible-radio board. e.g: BRD4162A

NOTE: Tested boards for working with this example:

Board ID	Description
BRD2703A	EFR32xG24 Explorer Kit - XG24-EK2703A
BRD2704A	SparkFun Thing Plus Matter - MGM240P - BRD2704A
BRD2601B	EFR32xG24 Dev Kit - xG24-DK2601B
BRD4314A	BGM220 Bluetooth Module Explorer Kit - BGM220-EK4314A
BRD4108A	BG22 Bluetooth SoC Explorer Kit - BG22-EK4108A

Connections Required

• Connect the Bluetooth Development Kits to the PC through a compatible-cable.

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.

Create a project based on an example project

1. 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 "controlling led".

2. Click Create button on the Bluetooth - Controlling LED from Smartphone 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 new Bluetooth - SoC Empty project.

2. Copy all attached files in inc and src folders into the project root folder (overwriting existing).

3. Import the GATT configuration:

   • Open the .slcp file in the project.

   • Select the CONFIGURATION TOOLS tab and open the Bluetooth GATT Configurator.

   • Find the Import button and import the attached config/btconf/gatt_configuration.btconf file.

   • Save the GATT configuration (ctrl-s).

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

   • [Services] → [IO Stream] → [IO Stream: EUSART] → default instance name: vcom
   • [Platform] → [Board] → [Board Control] → enable Virtual COM UART
   • [Application] → [Utility] → [Log]
   • [Platform] → [Driver] → [LED] → [Simple LED] → default instance name: led0

5. Build and flash the project to your device.

Note:

• Make sure that this repository is added to Preferences > Simplicity Studio > External Repos.

• Do not forget to flash a bootloader to your board, see Bootloader for more information.

How It Works

1. Start EFR Connect application on your smartphone

   Note that both Bluetooth and Location are required to use this App.

2. Select Bluetooth Browser.

3. Find the device called "LED Control" and press Connect button to connect.

4. In the Automation IO service, find the Digital characteristic.

5. Press the Write button of the characteristic then change the state to Active or Inactive. You should see the LED turning on or off.