Switching time between channels for nRF52840 for RSSI sniffer

RE: Switching time between channels for nRF52840 for RSSI sniffer

Nop Microwave — Wed, 20 Nov 2024 12:51:23 GMT

Thanks

RE: Switching time between channels for nRF52840 for RSSI sniffer

Sigurd — Wed, 20 Nov 2024 11:41:23 GMT

Hi!

In the SoftDevice Controller we have a feature called QoS Channel Survey, it measures and gives the RSSI on the 40 BLE channels. AFAIK, this takes around 3ms. So, 3000us / 40 = 75us per channel.

RE: Switching time between channels for nRF52840 for RSSI sniffer

Nop Microwave — Wed, 20 Nov 2024 09:37:43 GMT

Hi,

So I guess that the whole timing is included into th folowing the 3 following lines:

t_{RXEN,FAST,IEEE 802.15.4}

Time between the RXEN task and READY event after channel FREQUENCY configured (IEEE 802.15.4 with fast ramp-up)

µs

t_{RXDIS,IEEE 802.15.4}

When in RX, delay between DISABLE task and DISABLED event (IEEE 802.15.4)

0.5

µs

RSSI_PERIOD

RSSI sampling time from RSSI_START task

0.25

µs

which might be, assuming some extra overhead SW tasks, less than 50 us polling rate between each frequency sniffed.

Do you confirm ?

Thanks

RE: Switching time between channels for nRF52840 for RSSI sniffer

Sigurd — Tue, 19 Nov 2024 23:03:29 GMT

Hi!

[quote user="Nop Microwave"]But it assumes that the Radio was not READY befoir the channel modification.[/quote]

To change FREQUENCY, the radio need to be in DISABLED state.

RE: Switching time between channels for nRF52840 for RSSI sniffer

Nop Microwave — Tue, 19 Nov 2024 13:46:05 GMT

Hi,

Thanks for this update. In fact, I have alreday taken a look at these numbers.

My concern is the time, when the radio already in RX READY, to switch from one frequency (eg 2400 MHz) to another (eg 2420 MHz), keeping the radio in RX. It's like a spectrum analyser, the receiver is sweeping from on frequency to another.

The closest specification provides this

"Time between the RXEN task and READY event after channel FREQUENCY configured (IEEE 802.15.4 with fast ramp-up) : 40 us".

But it assumes that the Radio was not READY befoir the channel modification.

Can you provide some numbers ?

Thanks.

Nop

RE: Switching time between channels for nRF52840 for RSSI sniffer

Sigurd — Tue, 19 Nov 2024 13:29:37 GMT

Hi!

You can find some numbers on this here:

https://docs.nordicsemi.com/bundle/ps_nrf52840/page/radio.html#unique_2124379074