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How to Convert RSSI Value(dB) into Distance(m) In STM32WB

Associate III


          In My Project  I have to findout the distance between BLE Master(p2p Server) and Slave(p2p Slave) using STM32WB5MMG and i got the RSSI value using api hci_read_rssi() ,anyone help me to convert RSSI value into distance.

  p2p Server  TxPower +3dB and p2p Client TxPower is  -0.15dbB

  WhatsApp Image 2024-04-22 at 4.17.21 PM.jpeg

Andrew Neil
Evangelist III

You can't.

RSSI is affected by so many things that the best you'll achieve in practice is just a very broad "near" or "far" guesstimate.


Associate III

@Andrew Neil 

I thought ,the one of the  main action of STM32WB series is tracking ble device and tracking ble device using rssi is possible ?

Only very crudely using RSSI alone.


Most applications don't operate in a vacuum.

Might work within a room within LoS


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@Tesla DeLorean 

    In My project its woking inside the room and now the difficulty is Rssi to Distance in metre.

So try it - log RSSI against position in room.

Don't forget that "position" is in three dimensions.

Be sure to take multiple readings in each position

See how much it varies with, for example:

  • the number of people in the room
  • the orientations of devices
  • the number of other devices in the room



Another thing to do would be to leave your unit in a position for an extended period, and log the RSSI - see how much it varies for a stationary unit.