Distance from RSSI field- NRF52-DK.

[Pradeep Chl]

I have a NRF24LE1 transmitter transmitting 10 bytes of static payload every sec.

While I have a Receiver which is NRF52-DK. It is receiving the payload that is sent by the transmitter.

I am using NRF5-SDK 11.0 and modified to suit my transmitter configuration. I am getting the rssi field value in the range of 60 to 80 for every tag detected. I am assuming this number is the power received in dB but positive value. How do I get the distance from the transmitter to receiver with the rssi value.? I am using esb_rx under proprietary_rf folder, I am using the same rx except addresses, crc, datarate, payload_length are changed.

[tesc]

Hi,

First note that the RSSI value can only be used for rough distance estimates, as it both depends on environmental factors and has some deviation. Further, it also depends on the RF properties of the device (which again depends on antenna, matching network and form factor of the device).

Because of the above we can not possibly have any general purpose formulas or conversion tables for RSSI to distance calculations. You should do your own meassurements, with the final devices, to find a formula or to generate a conversion table. You can have a look at this question Regarding nRF51822 RSSI to Distance Calculation for some more input.

Regarding the RSSI field value, are you sure that you interpret the value correctly? The value contained in the nrf_esb_payload_t::rssi field is of type int8_t, which is a signed integer. -50 to -70 dBm sounds like a reasonable range, might it be that you are interpreting an int8_t value as if it was a uint8_t?

Regards, Terje

[tesc]

See also some comments regarding RSSI measurements in the answer and comments to this question on RSSI variance.

[Pradeep Chl]

Although nrf_esb_payload_t::rssi field is of type int8_t(singed integer), I am receiving a positive value. I am printing it with, NRF_LOG_PRINTF("RSSI = %d", rx_payload.rssi);

Am I doing some thing wrong here ?

Thanks,