Switching time between channels for nRF52840 for RSSI sniffer

[Nop Microwave]

Dear,

We are using the nRF52840 with a proprietary protocol.

We plan to use the nRF52840 to sniff/poll RSSI on different (5/6) channels on periodic time (typ ~100 us).

Can you share with me some timings values to proper read RSSI, change channel, read RSSI, change channel, read RSSI,change channel ...

The radio will always be in receive mode.

Thanks.

Nop

[Sigurd]

Hi!

You can find some numbers on this here:

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

[Nop Microwave]

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

[Sigurd]

Hi!

Nop Microwave said:

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

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

[Nop Microwave]

Hi,

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

tRXEN,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)	40		40	µs
tRXDIS,IEEE 802.15.4	When in RX, delay between DISABLE task and DISABLED event (IEEE 802.15.4)	0.5		0.5	µs

RSSIPERIOD

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

[Sigurd]

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.

[Nop Microwave]

Thanks