nRF24/RF24

Get Signal Strength

Closed this issue · 3 comments

justcallmekoko commented

Describe the behavior you would like

I would like to have a public method available which would allow the user to get the signal strength from the most recently received data. Perhaps whatever is received during a period of listening. In addition to having methods like testCarrier or testRPD, there could be a separate method to call to retrieve the signal strength of the transmission which would be related to testCarrier etc. i.e. if testCarrier returns true, the user can call carrierDPM or something and it returns the signal strength value.

Propose an implementation or solution

No response

Describe alternatives you have considered

I do not personally understand the registers of the nRF24L01+ enough to attempt an alternative solution but since there exists a testRPD method which has a dpm threshold, I imagine there is already a way signal strength is being measured.

Additional context

I am creating a frequency analyzer which will display a graph representing the number of transmissions received within a certain amount of time before plotting the next point on the graph. The graph is to be color coded based on the average strength of the signal received during that time.

2bndy5 commented

This isn't possible with the nRF24L01

It is possible with the nRF5x radios, but the SPI interface for the nRF24L01 only allows reading the RPD flag. The signal strength is mostly implied from facts stated in the nRF24L01 datasheet.

  • available() -> true means signal (for latest payload received) was at least
    • -82dBm sensitivity at 2Mbps
    • -85dBm sensitivity at 1Mbps
    • -94dBm sensitivity at 250kbps
  • testRPD() -> true means signal in the channel was present and detected with at least -64dBm or better

See our scanner example for the best-guess attempt. We also have scannerGraphic example (requires a display) that tracks the the history on every channel and uses that to calculate peak decays. The scannerGraphic could be better, but we're ultimately limited by the nRF24L01 interface.

2bndy5 commented

And certain PA/LNA variants obviously have different sensitivities as well. There's just no way we can read the signal strength given the SPI interface for the nRF24L01 chip.

justcallmekoko commented

Thank you for the information. I was not aware of the limitations of the IC itself.