EFR Connect Mobile App


The Silicon Labs EFR Connect app uses the Bluetooth adapter on your phone/tablet to scan, advertise, connect, and interact with BLE devices. It is available for Android and iOS and provides Bluetooth firmware application developers with a tool that can help them test and troubleshoot their application across the entire development life cycle.

It's a mobile application made by developers, for developers, with advanced features that allow you to easily search, connect, and exchange data with your Bluetooth device, as well as perform OTA updates on Silicon Labs Bluetooth devices.

This application has two main functional areas, the demo and the develop view. By default, the app opens in the Develop view and the selection between them is achieved through the two icons on the bottom side of the app, as shown in the Demo view and Develop view sections.

The demo view lists demos used to quickly test sample apps in the Silicon Labs Bluetooth SDK. The currently supported demos are:

The Develop view contains features focused on helping developers create and troubleshoot their Bluetooth applications based on EFR32/BGM devices. The currently supported features are:

The EFR Connect mobile application source code for both iOS and Android is available on GitHub under the Apache 2.0 license.

EFR Connect mobile app is under constant development with new demos and developer-focused features introduced over time, which will be added to this document.

This version of the document refers to the version 2.0.3 for both iOS and Android app. Because the apps have the same UI for most features, this document uses screen shots from the Android app. For a UI feature that affects how the user interacts with the app, screen shots from both apps will be shown and an explanation will be provided for each separately.

Demo View

Demo view shows a selection of demos used to quickly test and demo sample apps in the Silicon Labs Bluetooth SDK.

Health Thermometer

This demo scans for devices that advertise the Health Thermometer service (UUID 0x1809). Once connected, it subscribes to indications from the Temperature Measurement characteristic (UUID 0x2A1C). Because the indications are received by the app, the temperature value is displayed.

Searching for Health Thermometer devices

Connected to a thermometer device and receiving data via indications

Use this demo with the SoC-thermometer sample application from the Silicon Labs Bluetooth SDK. For more information, see the Getting Started section of the Bluetooth documentation.


From either Demo or Develop view you can access the Info screen through the icon on the upper right corner. The Info screen brings up a dialog with useful information about Silicon Labs products, links to the GitHub repositories, app stores as well as Bluetooth documentation (including this User's Guide).


Develop View

The develop view contains a collection of tools focused on Bluetooth firmware application developers. Currently, this consists only of the Browser and the Advertiser. They contain a number of advanced features that will be covered in the subsequent sections.

Develop View

Browser View

The browser allows you to scan, connect, and exchange data over GATT with Bluetooth LE devices around you. When you access the browser from the Develop view, it automatically starts scanning and populating the screen with cards that represent each of the scanned devices. The devices appear on the list in the order in which they are discovered. As a result, to see new devices, scroll down the list.

Device Cards

Each device discovered by the app is represented by a card containing information about that device.

Main Browser

The image above shows the main elements of the device card which are as follows:

  1. Device name, if it's part of the advertisement, either through AD type Complete Local Name (0x09) or Shortened Local Name (0x08). If the device name is not part of the advertisement packet nor the scan response packet, the app will display "N/A".
  2. The star indicates whether the device has been marked as favorite (star with blue color). This can be easily toggled by tapping the star, which makes it gray. If a favorite device is found, it automatically surfaces to the top of the list, regardless of the order in which it is found relative to the other devices.
  3. Advertisement interval in milliseconds.
  4. Connect button if the advertisement is of connectable type.
  5. Bluetooth address. Note: On iOS the Bluetooth address is not accessible to the application.
  6. Indication of whether the advertisement is connectable or non-connectable.
  7. RSSI (Received Signal Strength Indicator).
  8. Indication whether the advertisement complies with a known beacon format (iBeacon, eddystone or Altbeacon). If no beacon format is identified, it will be "Unspecified".

The device card can be expanded by tapping anywhere on the card other than the Star or the Connect button. When tapping on the device card, it expands showing the advertisement data details. Another tap will collapse it. When expanded, each row shows one of the advertisement data types which are part of the advertisement data.

Browser Advertising Details

If the advertisement is a known beacon format, the details are also parsed according to that specific beacon format. The image below shows the details from an iBeacon advertisement (soc-iBeacon sample application running on an EFR32BG22 kit)

Browser Advertising Details Beacon

EFR Connect also supports extended advertising, however, that must also be supported by the specific mobile device where the app is running. If the phone supports it and devices are sending extended advertising, that will be visible at the top of the advertisement details.

Browser Extended Advertising

Start and Stop Scanning

The user can control when scanning starts and stops. There are only four situations where the app does this automatically:

Scanning will continue indefinitely until the user taps the Stop Scanning button at the bottom side, which will toggle the button color to blue and the text to Start Scanning.

Start/Stop action does not clear the list of devices, which means that if scanning resumes with an existing device list, new devices will be added to the end of the list.

Pulling down and releasing the device list causes the list to refresh. As mentioned above, this will also automatically start scanning if it was stopped.


The filter allows narrowing down your search to a list of devices that fulfills a specific set of criteria. To reach the filter tap the Filter icon on the top right corner which will reveal the filter options on a pull-down.

Browser Filter

To collapse the filter, either tap the filter icon or the X icon on the lower right hand side.

The filter allows searching for devices with the following parameters:

Touching the Search option causes the new filter parameters to take effect, which also automatically collapses the filter. An active filter can be visible in the filter icon where a small check mark is added.

Tapping Reset clears all the filter parameters and collapses the filter. The filter will be applied to the list of devices regardless of whether scanning is on-going or not.

You can also save an existing set of filter parameters for later use. To save filter selections, touch the Save button. Saved filter parameters are listed in the Saved Searches at the bottom of the filter pull-down.

Browser Filter Saved Searches

Loading filtering parameters can be done by touching a saved search. The selected saved search is marked with blue font. To delete a saved search, tap the garbage bin on the right hand side. To take the newly loaded filter parameters into effect, tap the Search button.


The connection drop-down lists all active connections, which allows the user to go into each of those connection views or disconnect from those devices. Devices can be disconnected individually through each device's Disconnect button or altogether with the Disconnect all button at the bottom.

Browser Connections

You can also disconnect from devices from the main browser view, if they are listed in the scan list. Connected devices have a Disconnect button in red color instead of the blue Connect button.

Browser Connections

If the scan list is refreshed, those devices are likely to disappear from the list unless they continue advertising after a connection has been established.


The log keeps a record of all the Bluetooth activity. It can be shared via email or other methods for later analysis, filtered via text based search, and cleared.

Browser Log

Mappings Dictionary

The mappings dictionary can be accessed via the dictionary icon on the top right of the browser main view, which contains a list of all the 128-bit UUIDs that have been renamed by the user. Within the mappings dictionary, the user can further edit their names as well as delete them.

Browser Mapping Dictionary

Device View

When either a connection with a device is established or the user goes to an existing connection via the connections pull-down, the app will go to the device view where it displays the remote devices' GATT database.

GATT Services

Each card represents a GATT service and contains the service name and UUID. A custom service (128-bit UUID), which has not been renamed by the user is displayed as Unknown service. Similarly, a custom characteristic, which has not been renamed, displays as Unknown characteristic. One exception to this is the Silicon Labs OTA service (UUID 1D14D6EE-FD63-4FA1-BFA4-8F47B42119F0) and all its characteristics, which cannot be modified.

Device Main View

GATT Characteristics

Tapping anywhere on the card causes it to expand, which reveals the characteristics within that service as well as the supported properties for each characteristic (e.g., read, indicate).

Device View Characteristics

Tapping into a characteristic causes it to expand further and expose data within the characteristic. This will not automatically read the characteristic, which means that the data fields may be empty. Reading needs to be done explicitly by the user (if the property is available) by tapping the Read icon.

Device View Characteristics

If other properties are available, they will have additional associated icons. For characteristics without any specific data format, you can copy data to the clipboard with the copy icon on the right side of the characteristic data. Data will be copied using the respective format (hex, ascii, or decimal).

Device View Characteristics

If the write property is available for instances, when tapping the write icon it brings a dialog that allows writing data into the characteristic.

Within that dialog, you can select which write operation to use (write request or write command) depending on what is supported by the characteristic. If one is not supported, it will be grayed-out.

You can also paste data from the clipboard by using the paste button on the right side of the characteristic data. Data you paste in must have the same format as the field where it is pasted or the app will throw an incorrect format error.

Device View Characteristics

Note: On iOS, write request (Write) and write command (Write no Response) have separate icons as part of the characteristic properties.

Device View Characteristics

GATT Descriptors

If a characteristic has descriptors, they are listed underneath the characteristic UUID.

Device View Characteristics

Additional Options

In the Device view, the user retains access to the Log and the list of connections so that it is easy to swap between connected devices. An RSSI value, which is refreshed each second, is located in the top right hand corner. Furthermore, there is a menu with additional options.

Device View Characteristics


Over-the-air device firmware updates (OTA DFU) allow updating a device with a new firmware sent over a Bluetooth connection. OTA option is shown in the menu if the Silicon Labs OTA service is included in the GATT, in which case it is assumed that the device supports OTA.

Tapping into that option opens a dialog with the following options:


During the OTA process, information about progress is displayed until OTA is finalized.


For additional guidance on OTA process using EFR Connect,see Using EFR Connect Mobile App for OTA DFU.

Advertiser View

The advertiser allows you to use the mobile phone as a BLE peripheral by creating and customizing advertisement sets, both in terms of their configurations as well as payload.

This functionality comes in handy when you have a single Silicon Labs kit for a Bluetooth product, but you still want to test/evaluate/develop applications that leverage the Silicon Labs Bluetooth stack functionalities as a central device.

Creating New Advertisement Sets

When entering the Advertiser for the first time, the user sees an empty list of advertisement sets because none have been created yet.

Advertising Main

By tapping the menu icon on the top-right corner of the main advertiser view, the user is presented with the following options:

Advertiser Main Menu

Selecting Device name brings up a dialog to change the device name, which is a global setting and cannot be set individually for each advertisement set.

Advertiser Device Name

Create new adds a new advertisement set that only includes the flags AD Type in its payload. The advertisement set is represented by a card, similar to the device representation in the Browser.

Advertiser Main

The image above shows the main elements of the device card which are as follows:

  1. Name of the advertisement set. This is not the device name but simply a way for the user to identify each advertisement set.
  2. TX Power in dBm
  3. Advertisement interval in milliseconds
  4. Copy control. This creates an exact copy of the advertisement set which is added at the end of the list of advertisement sets.
  5. Edit control. Takes the user to the edit view of a specific advertisement set.
  6. Delete control. Deletes the specific advertisement set.
  7. Enable/disable advertisement set.

If the user taps the delete control, there is a confirmation prompt which can be dismissed on further delete actions.

Advertiser Delete Set

When tapping the device card, it expands with further advertisement details in the same way as device cards expand on the Browser when tapped.

Advertiser Main

Editing Advertisement Sets

When entering the edit view for a specific advertisement set, the user is shown a list of customization options. Those options are divided into three areas:

The view header displays the name of the advertisement set name, which can be changed via the very first text box at the top.

This is followed by the advertisement type, which can be selected between Legacy Advertising and Extended Advertising (introduced in Bluetooth 5.0 specification). Support for Extended Advertising depends on the underlying mobile phone and OS stack. If not supported, a note is displayed and the Extended Advertising option will be grayed out.

Advertising Settings

The following Legacy Advertising types are supported:

Advertiser Settings

Extended Advertising supports the following types:

Advertiser Settings

TX power can be optionally included as part of extended advertising, and, if the type is non-connectable, non-scannable, it can optionally be set as anonymous advertising.

Depending on the selected advertisement type, the Advertising Data and Scan Response data will be available for editing. For example, a connectable, non-scannable type does not have scan response so the Add Data Type button for Scan Response Data will be grayed out.

Advertiser Settings

Data is added by tapping Add Data Type and selecting which data type to add.

Advertiser Settings

The following advertising data types are currently supported:

The selected data type will be added to the advertisement data and below Add Data Type button the amount of bytes still available is shown.

Advertiser Settings

When adding AD types 0x03 or 0x07, each service needs to be added individually by tapping Add 16-bit service or Add 128-bit service buttons.

Advertiser Settings

Services are added via a dialog box where the user can input the service UUID or name. For 16-bit services (so called adopted services), an auto-complete functionality suggests services as they are being typed into the text box. Below the box, a link Bluetooth GATT Services takes the user to the Bluetooth SIG Web page that lists all adopted services.

Advertiser Settings

Multiple services can be added under the 0x03 and 0x07 AD Types and can be individually deleted by tapping the trash bin icon. If the trash bin icon for the AD type is tapped, all services are removed together with the AD Type.

Advertiser Settings

Advertising Parameters are below the advertising data and scan response data options. These allow the user to select the advertising PHYs, advertising interval, and TX Power. Lastly, an advertising limit can also be selected for the advertising set, which automatically disables the advertisements after a set time period of a number of advertisement events.

Advertiser Settings

The advertising PHYs for the primary and secondary channel depend on support from the underlying smartphone and OS. They are only available if extended advertising is supported. The alternative PHYs for each of the primary and secondary channels will be available in the respective drop-down menus.

Advertiser Settings