Bluetooth trilateration and direction tracking using nrf52840

[sibi]

hello i am new to the nrf trilateration and direction tracking using nrf52840, i need some help with the sdk and programming and working examples .

eg : I have 4 nrf52840 with this how to track the direction using the trilatreration method with sdk availble in the nrf sdk?

1)If it is possible what are the steps for programming

2)how the the working will hapen any referencs (how to see the direction using mobile app or wow to do that ?)

[Einar Thorsrud]

Hi,

The nRF52840 does not support direction finding (AoA/AoD) unlike for instance nRF52833. And unlike nRF54L series, it also does not support channel sounding. If you are starting a project now I would strongly consider nRF54L and channel sounding.

If you have to use nRF52840 the only option is to monitor RSSI. But note that this is not a very good measure of distance, as various obstacles attenuate the signal, and you also have reflections/multipath. In a nutshell, if you measure a high RSSI, the transmitter is likely close. If you measure a low RSSI, the transmitter may be fare away, but not necessarily.

I do not have any examples of trilateration, but for a scanner the RSSI is reported with the scan report. See for instance how this is done in the basic Zephyr central sample. (For reading the RSSI in a connection, you can refer to this post).

[sibi]

Hi,

Thanks for reply

I have some doubts 

I refered the webinar https://www.youtube.com/watch?v=AtS6HsrUgZQ from nordic youtube channel 

In the webinar i noticed they are using u-blox for antenna but how the connection from nrf52833 is connected to ublox

how to program ublox or nrf52833 (eg: https://share.google/WM8YDfhdtzYmdxBVM in this direction finding peripheral and central sdk will support for nrf52833 with u blox?)

without the ublox can we test the AoA for nrf52833 for direction finding with the nrf52833 dk board itself?

Is that necessary to use ublox or use default antenna in nrf52833 dk board or use other antenas ?

[Einar Thorsrud]

Hi,

Direction finding requires multiple antennas / antenna array in one of the ends (which depend of if using AoA or AoD), so you cannot use the nRF5340 as is. You can read more about this in the Direction Finding whitepaper and the documentation for the direction finding samples in the SDK:

• Bluetooth: Direction finding central
• Bluetooth: Direction finding connectionless locator
• Bluetooth: Direction finding connectionless beacon
• Bluetooth: Direction finding peripheral

The need for muliple antennas is a down side with direction finding (as is also multipath effects). Depending on the use case using channel sounding to determine range is often a better option. This is only supported with nRF54 series devices, though.