Calculating RSSI without receiving user messages

RE: Calculating RSSI without receiving user messages

P Sumanth — Thu, 04 Apr 2019 10:41:32 GMT

Yes it worked Thank you

regards

sumanth

RE: Calculating RSSI without receiving user messages

Hung Bui — Thu, 04 Apr 2019 10:08:47 GMT

I don't see any problem with that. You can request the softdevice to report RSSI when there is any change in RSSI using sd_ble_gap_rssi_start() there is a threshold value and skip count that you can configure. Have a look here.

Should have pretty low power consumption with 300ms interval. You can calculate the estimated power consumption here.

RE: Calculating RSSI without receiving user messages

P Sumanth — Wed, 03 Apr 2019 15:53:02 GMT

Yes I know that, My idea is if two devices connected through BLE and when they are out of range it should generate some alert (ex-buzzer). I am using nrf52 DK. I will be using about 30-40 devices later(star network), power consumption is major factor i am considering,

Right now I am working on BLE central and peripheral, I am able to calculate the RSSI of peripheral before and after the connection.

I would like to use that RSSI, I am thinking to take RSSI reading for every 300ms, total of five times and take the average of it and compare with the reference value, Is that possible with low power consumption or is there any other way to do it?

RE: Calculating RSSI without receiving user messages

Hung Bui — Wed, 03 Apr 2019 15:02:23 GMT

You would need to give us your exact application definition and requirements to be able to give you advice. You can convert this case to private if there is confidential information.

To get the distance between connected device, you can use RSSI. But be aware that RSSI is relative and can't be used to calculate the exact distance to a node. It can be affected largely by for example if a human is stand between the devices, if there is some reflection etc.

RE: Calculating RSSI without receiving user messages

P Sumanth — Wed, 03 Apr 2019 04:28:49 GMT

I would like use BLE since we need to restrict power consumption, What will be the procedure for that.(star network) to find the distance between the connected devices .

RE: Calculating RSSI without receiving user messages

Hung Bui — Tue, 02 Apr 2019 16:06:32 GMT

It's still possible to use BLE to connect a network with 40 nodes (by using multiple of BLE star network) But mesh maybe a better solution if power consumption is not your concern.

I would suggest to study the mesh spec to have a rough idea of Heartbeat how it's configured. And then check the example to see the modification made in node_setup.c and provisioner_helper.c file that I did.

Mainly it's about sending a configuration message to the configuration server to enable subscription and publication of heart beat.

RE: Calculating RSSI without receiving user messages

P Sumanth — Tue, 02 Apr 2019 11:36:41 GMT

The number of devices will be around 40 and for now I working on 3 devices so i am choosing mesh, right now I am using nrf52 DK for the setup and i am little familiar with nrf Mesh SDK like creating custom models and looking forward to work more on mesh SDK.

Regards

Sumanth

RE: Calculating RSSI without receiving user messages

Hung Bui — Tue, 02 Apr 2019 11:25:08 GMT

Hi Sumanth,

How many devices you have in the network ? What is the setup of the application ? I need to ask because if you have less than 20 devices and they are all in the range of the central device, you can think of using BLE instead of Mesh.

Are you familiar with our mesh SDK ?

RE: Calculating RSSI without receiving user messages

P Sumanth — Tue, 02 Apr 2019 05:43:19 GMT

Hey thanks and I have gone through the specs, My idea is I have two devices, one which publishes the data and other which subscribe, they should blink the led when both are out of range(ref distance), I want to do it in mesh because I have multiple publishers and one device that subscribes all publishers. I have also seen the post

https://devzone.nordicsemi.com/f/nordic-q-a/39270/ble-mesh-heartbeat-example

but couldn't understand the procedure, If possible explain the procedure and configuration of heartbeat messages and finding rssi?

Regards

Sumanth

RE: Calculating RSSI without receiving user messages

Hung Bui — Mon, 01 Apr 2019 13:12:25 GMT

Hi Sumanth,

I think you maybe confused between Bluetooth Low Energy and Bluetooth Mesh. They are not the same. Bluetooth Mesh doesn't have empty packets to keep the connection, there is no connection in Bluetooth mesh.

But what you can do is to send HeartBeat packet instead. It's made for this purpose. Please have a look at section 3.6.7 in Bluetooth mesh spec v1.0

You would need to configure the server to send heartbeat to a particular group address, and then configure other node to subscribe to that address.