wifi detection to avoid interferance

[Larry Harmon]

Is it possible to use an nrf51822 to detect Wi-Fi channels / frequencies in use for the purpose of avoiding them?

[Øyvind Karlsen]

Hi,

Yes, to a certain degree. The nRF5 series can sample indicent power at the antenna port by using the RSSI module.

If using BLE this is already implemented, the channel map for BLE is aligned so that it is the least likely to receive interference from WiFi (the main source of interference in the 2.4 GHz band), and it also implements frequency hopping when a channel is too bad to get data through.

Best regards,

Øyvind

[Larry Harmon]

Thanks!

We are not using BLE, just direct radio control. I wrote a simple test which reads the RSSI 1000 times on each frequency from 2.401 thru 2.482. I seem to be getting reasonable results, but I'm curious how BLE samples RSSI values. Does it scan all frequencies? Does it take multiple RSSI samples per frequencies? How oftes?

[Øyvind Karlsen]

I am not 100% on the specifics, but I think it will make the decision to change based on high percentage of packet losses, after it decides the packet loss is too high it will start a renegotiation procedure. Details are covered in the BLE core manual.

For your purpose I guess the easiest would be to sample packet throughput in your application, and if it gets too bad you can have a set of frequencies (perhaps in between the most common wifi channels) where your transmitter/receiver will go to and renegotiate the terms of connection (perhaps based on a scan of the channel map).