The encryption and signature for the OTA file comes from the bootloader. The apploader just provides a way to transfer that file to the SoC over BLE.

You don't have to redesign apploader as such and we provide guidance and example of application level OTA which should get you up and running quite easily. You can find this in AN1086: Using the Gecko Bootloader with the Silicon Labs Bluetooth® Applications, chapter 4.

YK is mostly right, except that it's not simultaneously in the literal sense because you cannot send packets on different frequencies at exactly the same time. The packets are sent with a small delay in between them which can vary depending on whether you are sending scannable advertisements or not, and if you are then it also depends if a central device sends a scan request to which the stack will respond to with a scan response.

More info in the Bluetooth 5.2 core spec, Vol 6, Part B, section 4.4.2.

Unfortunately there is no timeout, once you trigger the apploader it will stay in that state until you reset it back to the application. 

If you need this feature you have to use application level OTA which gives you complete control.

const uint8_t advdata[] = {'T', 'e', 's', 't'};

This advertisement data is not conformant with the standard. For that reason the scanning devices are probably dropping it because they don't know how to display it. You need to create properly formatted data which follows the standard.

This can help: https://docs.silabs.com/bluetooth/2.13/general/adv-and-scanning/bluetooth-adv-data-basics

Yes, you can use a lower API version, you just need to change minsdkVersion inside of two build.gradle files, app build.gradle and bgxpress build.gradle.

Keep in mind that we are not testing with any version below Android 9 so you should do extensive testing of your app if you want to support a lower API version.

Hi,

BGX Commander is now supporting Android 9 and upwards, which is API level 28.

The framework is open source so if you wish to change the minimum OS version requirement you are free to do so, but as far as testing goes we only test with Android 9 and above.

Regards,

Tiago

-) I would like to add the possibility of debugging (from the outside) of my target board. To do this, I would like to add ISA3, MINI, CORTEX connectors to my target board project, and connect these lines to EFR32BG13.

Why would you need all 3 connectors? They have redundant functionalities between them. We recommend using just mini-simplicity as it should have all the functionality you need (SWD, PTI and VCOM).

On the target board, can I directly connect the three Mini-Simplicity Connector connectors (ISA3, MINI, CORTEX) to the Bluetooth radio board?

What do you mean by this exactly? What is Bluetooth radio board in this context, your target custom hardware or something else?

Normally you have already decided which debug connector to use at the time you designed your hardware, what did you design-in?

Yes there is the thermometer client sample app in the SDK that scans for thermometer devices, connects and subscribes to indications.