How to get RSSI asynchronously & independent of any connection or events.

RE: How to get RSSI asynchronously & independent of any connection or events.

Karl Ylvisaker — Wed, 05 Aug 2020 09:17:25 GMT

Hello Christian,

Between what you are saying in this comment, and you reply to Turbos comment, I am not exactly sure what you are looking for.
By using radio timeslots you will indeed take control over the radio peripheral for some time, which I understand is not your intention.

[quote user="christianhahn"]What I meant by instantaneous was: irrespective of if a packet is being received or not, what is the value of the filtered RSSI measurement right now.[/quote]

The RSSI value is tied to a connection event - you may not sample the RSSI value independently of receiving packets. The sd_ble_gap_rssi_get function returns the RSSI value for the latest connection event.

[quote user="christianhahn"]I am not interested in taking over the entire radio or interfereing with the BLE operation. Nor am I interested in changed the receive frequency. I really just want to know the RSSI sampled by the receiver right now.[/quote]

If you would not like to control the radio directly, or have anything to do with the BLE operation, I would again recommend that you first call sd_ble_gap_rssi_start, and then use the previously mentioned sd_ble_gap_rssi_get function to report the RSSI value for the latest connection event. Alternatively, you could use the BLE_GAP_EVT_RSSI_CHANGED event if you are only interested in the RSSI value when it changes significantly.

[quote user="christianhahn"]How can I initiate the RSSISTART task on demand?[/quote]

If you would like the SoftDevice to stop reporting RSSI at any time, you can use the sd_ble_gap_rssi_stop function to do this.

Please let me know if anything still should be unclear.

Best regards,
Karl

RE: How to get RSSI asynchronously & independent of any connection or events.

christianhahn — Tue, 04 Aug 2020 23:04:02 GMT

Hi Karl,

What I meant by instantaneous was: irrespective of if a packet is being received or not, what is the value of the filtered RSSI measurement right now.

The nRF52840 product specification says:

"Sampling of the received signal strength is started by using the RSSISTART task. The sample can be read from the RSSISAMPLE register."

How can I initiate the RSSISTART task on demand?

I am not interested in taking over the entire radio or interfereing with the BLE operation. Nor am I interested in changed the receive frequency. I really just want to know the RSSI sampled by the receiver right now.

Thank you!

-Christian

RE: How to get RSSI asynchronously & independent of any connection or events.

christianhahn — Tue, 04 Aug 2020 22:19:57 GMT

Thank you Turbo. I had a suspicion that something like this was happening. I will look into the timeslot API. It would seem that there are few examples on how to use it with an S140 SoftDevice.

RE: How to get RSSI asynchronously & independent of any connection or events.

Karl Ylvisaker — Tue, 04 Aug 2020 11:34:04 GMT

Hello,

What Turbo is saying is correct, you may not access the SoftDevice's registers directly.
However, you may use the SoftDevice's API to get the RSSI value, please see the sd_ble_gap_rssi_get function from the S140 v7.0.1 API reference.

[quote user=""]instantaneous[/quote]

Could you elaborate what you mean by instantaneous here? The SoftDevice will not prioritize the rssi_get function call from the application over internal function calls.
So, depending on what the SoftDevice is doing at the time of the rssi_get call, it might not return "instantaneous" per say.

Please do not hesitate to let me know if this was not what you were asking about.

Best regards,
Karl

RE: How to get RSSI asynchronously & independent of any connection or events.

Turbo J — Mon, 03 Aug 2020 12:16:13 GMT

[quote userid="92407" url="~/f/nordic-q-a/64458/how-to-get-rssi-asynchronously-independent-of-any-connection-or-events"]Can I use the RSSI registers directly while using a SoftDevice?[/quote]

Nope. The radio peripherial is blocked - except during timeslot events. Look into using radio timeslot API.