Central and Peripheral Role Switching and Nearby Device Discovery in nRF52832

[siltvm]

Hi,

I am currently working on a project using the nRF52832 controller as a gateway device and the nRF52810 controller as a timer indication device.

I have successfully integrated the Timer and SAADC peripherals into the ble_app_uart/pca10040e/s112 example project from the nRF5 SDK, and flashed it onto the nRF52810-based timer indication device. The device connects with the mobile app (APK) and is able to send and receive commands.

As discussed earlier, the project has evolved, and we have added an nRF52832-based gateway device. This change requires the nRF52832 gateway device to act as both a Central and Peripheral.

Requirement :-

Initially, the nRF52832 gateway device connects with the APK and sends the list of nearby available BLE devices to the APK, acting as a Peripheral. When the APK sends a command containing the name or MAC address of the desired device, the gateway device switches from Peripheral to Central role and connects to that corresponding timer indication device. This is the core requirement of my current project.

Is there any example project available that I can start with?

Could you please guide me on the following:

1. Is there any available example project that can demonstrate how a device can act as both a Central and a Peripheral?
2. How can the role switching between Central and Peripheral be implemented in the nRF52832?
3. Is there an option to retrieve a list of nearby advertised BLE devices?

Your response will be greatly appreciated.

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Project Details:

• SDK: nRF5 SDK 17.0.2
• IDE: SEGGER Embedded Studio 5.42a
• Controller: nRF52832

Thank you for your support.

Best regards,
SILTVM

W1 TO W9 are the timer devices 

[Hung Bui]

Hi Stilvm, 
Could you describe a little bit more on your application ? How many time indicators you have ? What's the distribution in distance between them and the gateway ? 
If all is in the range of one single gateway you may not need multiple gateway. Also you may think of having a mesh network if the device is not running on a battery. 

Regarding your questions: 

Is there any available example project that can demonstrate how a device can act as both a Central and a Peripheral? 

yes, please take a look at the examples in \examples\ble_central_and_peripheral\experimental , maybe the best fit would be the \ble_app_hrs_rscs_relay

How can the role switching between Central and Peripheral be implemented in the nRF52832?

You can switch between roles or you can have both roles at the same time with no problem. The stack can handle multiple connections at the same time regardless if it's central role or peripheral role

Is there an option to retrieve a list of nearby advertised BLE devices?

You can listen to the BLE_GAP_EVT_ADV_REPORT when scanning and can parse the advertising packets to get the name, address. Please take a look at the \examples\ble_central\experimental\ble_app_hrs_nfc_c , in ble_m.c you can find how the advertising packets are parsed in on_adv_report(): 
 

[siltvm]

 hi  , Hung Bui 

Sorry for the late response; we had a holiday for the past few days.

I’ll describe more about my application.

We have an nRF52832 gateway device and an nRF52810 timer indication device (we call it as "watches").

The firmware for the watch is almost complete, using the ble_app_uart/pca10040e/s112 example project available in the ble_peripheral example project directory.

The functionality of the watch is as follows:

                               The watch advertises its name and MAC ID, allowing us to connect to it via BLE using the nRF Connect Android application available on the Play Store. We can send and receive data using the Nordic UART service. I have also integrated timer and SAADC peripherals into ble_app_uart for timer indications and battery percentage observations, which are working fine.

Later, we decided to add a gateway device to manage communication between the nRF Connect app and the watch.

Project Requirements:

We need the gateway device to act as both a central and peripheral. Initially, the gateway device advertises as a peripheral, allowing it to connect via BLE using the nRF Connect app. Once the connection is successful, the gateway acts as a central, scanning for available nearby watches. It then sends the available devices' MAC IDs and advertised names to the app. The app will then send a command containing the MAC ID and BLE name of the desired watch to connect with the gateway device. The gateway then acts as a central to connect with the specified watch and The gateway device should provide the capability to send and receive commands between the app and watches.

Number of Timer Indicators(watches):

We haven’t set a limit on the number of watches that can connect to the gateway device at a time. It may be fewer than 20 .

Distribution Distance Between Watch and Gateway:

• The distance between the watch and gateway device is approximately ≤ 100 meters.
• The distance between the gateway and nRF Connect app is also ≤ 100 meters.

The purpose of implementing a gateway device between the watch and the nRF Connect app is to extend the communication range.

Mesh Network Consideration:

The watch is powered by a 135 mAh battery, whereas the gateway is USB-powered. This may present some challenges.

[siltvm]

Hung Bui , I see the example project ble_app_hrs_rscs_relay available in the BLE central and peripheral SDK directory, but when I try to build the code, an error occurs initially. I am attaching a screenshot for better understanding

[Hung Bui]

Hi Siltvm, 
It seems that the path is too long. Please try to copy the SDK to a folder near C:\ . You can rename the SDK folder from nRF5_SDK_17.0.2_dd674de to for example SDK1702. Windows only allow max length of the path to 250 characters. 

I don't see a problem with your set-up. Note that the gateway doesn't have to connect to all the watches at the same time. It can connect, read data and disconnect to connect to more device. This way even if you have more than 20 watches you still can get data from all of them. Of course if you have less than 20, you can just keep connections and don't have to do connect-disconnect. 

If you keep the connection, avoid using too short connection interval. Try 100ms and higher. 

[siltvm]

hi ,  Hung Bui . 

I changed the path as per your suggestion, so the error is resolved, and I am able to build the code. I just have a question on how to implement multirole meaning central and peripheral at the same time