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Reducing the range of BlueNRG-2N


Hello STMicroelectronics community,

I'm currently working on a project involving the BlueNRG-2N Bluetooth Low Energy (BLE) module, and I'm looking to reduce the Bluetooth range to approximately 1 or 2 meters (means over 2 meter, I want my bluetooth server side = a BlueNRG-2N chips inside a board   not detected by the client BT side = Smartphone ). The BlueNRG-2 module offers an extended range, and for my specific application, I need to limit the range to this shorter distance. After going through the BlueNRG-2 documentation and software development kit (SDK), I have identified that I should adjust the transmit power level to achieve this goal.

I have already located the aci_hal_set_tx_power_level function in the SDK, which allows me to set the transmit power in dBm.

I tried :

aci_hal_set_tx_power_level(0, 0); // Disable high power mode and set low power level

However, still Bluetooth can be detected from 4 meters !!! I'm seeking further guidance and best practices on how to configure this function optimally for a range of 1 to 2 meters. Additionally, if there are any other relevant parameters or settings that I should adjust to achieve this reduced range, please kindly advise.

To provide context, I have considered lowering the transmit power, adjusting the advertising parameters, and using non-connectable undirected advertising to limit the range, but I would appreciate your expert insights and recommendations on how to fine-tune these settings.

Here a resume for my research :

To reduce range :

* Lower Transmit Power  (I tested with lowest parameter but still up to 4 meters !!)

*Antenna Design (Use an Antenna with Reduced Gain): I cannot control this parameter at this moment !

* Modify the Bluetooth Advertising Parameters : I need more info about this !


Thank you in advance for your assistance. Your expertise will greatly contribute to the success of my project.

Best regards,