How to measure the distance between the nRF52840 and a smartphone using the Nordic Distance Measurement library?

[overclocker]

Until now, the distance between a other BLE module and a smartphone has been measured from RSSI.

For my use case, I thought that RSSI alone would be sufficient, since I only needed to know the relative value of the distance, not the exact distance.

However, since the relative values are also greatly affected by the orientation of the smartphone and signal conditions, we are considering alternatives.

I expected that the Nordic Distance Measurement library, which can be implemented in the nRF52840, would measure distances more accurately.

However, the sample code provided measures the distance between devices implementing the same Nordic Distance Measurement library.

Is it possible to use the Nordic Distance Measurement library in conjunction with a smartphone application such as Andorid or iPhone?

If not, are there other useful ways to measure distance besides RSSI?

Please let me know.

[Kazi Afroza Sultana]

Hello,

Is it possible to use the Nordic Distance Measurement library in conjunction with a smartphone application such as Andorid or iPhone?

No, It is not possible. The Nordic Distance Toolbox (NDT) is a set of methods for measuring the distance between two of Nordic's SoCs. One device configured as reflector and another device as initiator, so it could not support one of them be smartphone. Using signal strength (RSSI) for estimating distance is the inherent disadvantage of the technology for getting precise distance measurements. Since there are so many factors such as reflections and physical blocking effect the signal strength of the signal, hence the calculation of distance. 

Here is a slides of our distance measurement webinar you can look at https://devzone.nordicsemi.com/cfs file/__key/communityserver-discussions-components-files/4/Measuring_5F00_distance_5F00_with_5F00_Nordic_5F00_Distance_5F00_Toolbox_5F00_slides.pdf 

Here is the documentation of using Distance Measurement Library: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/libraries/others/dm.html

Thanks.

BR

Kazi

[overclocker]

Thank you for your answer.
I have also reviewed the documents you provided.

I also understood that the Nordic Distance Measurement Library uses various factors to measure distances and that smartphones cannot be used.

Conversely, is there a better way to measure the distance between the nRF52840 and the smartphone?

[Kazi Afroza Sultana]

RSSI is the simplest way of measuring between a phone and an nRF52 device. Even though it is not accurate. I am not aware of other better way, unless you have an nRF52 close to the phone, that uses the Distance measurement library to find the distance to the initial nRF52, and later to report the information to the phone.

[overclocker]

Thank you for your answer.

As it is difficult to have another nRF52 in my use case, I will use RSSI, knowing that it is not accurate.

Thank you very much.