Exploring LPN features in mesh_light_switch example

RE: Exploring LPN features in mesh_light_switch example

Elfving — Thu, 02 Nov 2023 12:20:16 GMT

Hello again, sand sorry about the wait

[quote user="mahesh vicky"]

this might be helpful in a few cases, but i think u misunderstood or i misconveyed my working scenario.

[/quote][quote user="mahesh vicky"]

any idea why this happens??

[/quote]

Yeah it might just be me being unclear about things.

It happens because the LPN is made to do so, when sending a message. It is a feature. It is made this way, because it might pay off in regards to power consumption. I guess if one assumes that the LPN will not be awake often, it would pay off to do the polling while it happens to be awake. That could require it to wake less frequently after all. In your situation however, as it wakes rather often, I guess it won't pay off.

So in your scenario I would recommend going for what I described below, where you rather work around it. The polling timeout is still something that is practical to take advantage of after all.

Regards,

Elfving

RE: Exploring LPN features in mesh_light_switch example

Vignesh R — Fri, 27 Oct 2023 15:34:10 GMT

[quote userid="103347" url="~/f/nordic-q-a/104418/exploring-lpn-features-in-mesh_light_switch-example/452536"]by calling "bt_mesh_lpn_poll()" API in custom k_delayed_work() based timing mechanism[/quote]

this might be helpful in a few cases, but i think u misunderstood or i misconveyed my working scenario.

when i send a normal mesh message(chat msg) , a poll is sent automatically even if the CONFIG_BT_MESH_LPN_POLL_TIMEOUT is not reached.

(i.e) if CONFIG_BT_MESH_LPN_POLL_TIMEOUT is set to 1 hr

and if i send a normal mesh message from lpn to friend at 5 min interval, for every 5 mins a poll is also sent to friend, and the friend responds to that poll too.

any idea why this happens??

hope i make sense:)

RE: Exploring LPN features in mesh_light_switch example

Vignesh R — Fri, 27 Oct 2023 15:23:20 GMT

[quote userid="103347" url="~/f/nordic-q-a/104418/exploring-lpn-features-in-mesh_light_switch-example/452324"]Any further thoughts on this part though, and your use-case for it?[/quote]

Please refer my previous reply,

[quote userid="116166" url="~/f/nordic-q-a/104418/exploring-lpn-features-in-mesh_light_switch-example/451196"]

In our mesh network, few LPN might be slightly a bit far away from its friend node, but communicable. So its recv_delay and poll_timeout can be adjusted according to the rssi level of that particular nodes.

And most importantly, for eg. if a friend node is very near to lpn, then its retry_count and timeout can be reduced smaller, so incase if its friend node dies, the lpn would try much lesser retrys and would goto sleep , and if this repeats for a given time, then it can try increasing its poll_wait and recv_delay, and in worse case if no friend node accepts for much longer time, then the node should decide itself to increase the poll_interval to higher values to save battery.

[/quote]

RE: Exploring LPN features in mesh_light_switch example

Elfving — Thu, 26 Oct 2023 11:53:52 GMT

When it comes to your example, what would probably be preferable then would be to simply use a large CONFIG_BT_MESH_LPN_POLL_TIMEOUT, the highest possible value that you will need in your application. And then execute friend polling at shorter intervals at shorter intervals, manually, by calling "bt_mesh_lpn_poll()" API in custom k_delayed_work() based timing mechanism in the application.

This way you can create any pattern of polling that you'll like. And if the polling stops, it will happen automatically from CONFIG_BT_MESH_LPN_POLL_TIMEOUT.

Lets assume t = 0 seconds, at the time friendship is established.

1. t = 0
schedule a delayed work to send a message after 40 seconds
schedule a delayed work to send a POLL manually after 30 seconds.

2. t = 30
manual polling delay work triggers at 30 seconds.
inside delayed_work callback:
call bt_mesh_lpn_poll()
reschedule a delayed work to trigger after 40 seconds (so, the next poll happens at t = 70 seconds)

3. t = 40
message sending delayed work triggers at t=40
inside delayed_work callback:
send a message (whatever it is)
re-schedule a delayed work to send a message after YY seconds

4. t = 70
manual polling delay work triggers.
inside delayed_work callback:
call bt_mesh_lpn_poll()
reschedule a delayed work to trigger after ZZ seconds (where ZZ must be < POLL_TIMEOUT (in seconds))

Regards,

Elfving

RE: Exploring LPN features in mesh_light_switch example

Elfving — Wed, 25 Oct 2023 14:42:13 GMT

Hello

[quote user="mahesh vicky"]how to avoid sending poll message when sending normal mesh message???[/quote]

Just letting you know that I am looking into if it can be turned off.

I do not believe it is required, but expected and a design choice. If one would like to wake up and send an additional message after all, it might pay off power consumption-wise, to do polling etc. right away, instead of waiting for that to time-out.

[quote user="Elfving"]FRIEND_REQ_RETRY_TIMEOUT, REQ_RETRY_DURATION, LPN_AUTO_TIMEOUT: Could be made runtime configurable. This is something we can think of as an enhancement. Could you give me a detailed use case describing how making this runtime configurable would help your use case? I see that this can be useful feature in some situations, but I would like to know the use case.[/quote]

Any further thoughts on this part though, and your use-case for it?

Regards,

Elfving

RE: Exploring LPN features in mesh_light_switch example

Vignesh R — Thu, 19 Oct 2023 07:35:36 GMT

[quote userid="103347" url="~/f/nordic-q-a/104418/exploring-lpn-features-in-mesh_light_switch-example/450977"]Could you give me a detailed use case describing how making this runtime configurable would help your use case?[/quote]

RE: Exploring LPN features in mesh_light_switch example

Vignesh R — Thu, 19 Oct 2023 06:58:50 GMT

Hey hi,

I have tried sending messages normally at regular intervals using a timer, and it worked fine.

and also found the following callback that serves the same purpose

BT_MESH_LPN_CB_DEFINE(lpn_usr_cb) = {

.established = &frienship_established,

.terminated = &friendship_terminated,

.polled = &friendship_polled,

};

This also works fine.

But the problem now im facing is that every message i send from lpn to a friend node using the chat model, the lpn also sends a poll message to the friend node and it responds with a poll ack. to it.

Sample scenario:

CONFIG_BT_MESH_LPN_POLL_TIMEOUT(poll_interval) - 30 sec

chat msg interval - 40 sec (A normal timer that sends a msg to a group at 40 sec interval)

1.Board boots

2.friendship gets established

3.30th second - a poll msg is sent to friend node and and ack. is received as response

4.40th second - a chat message is sent to friend (another poll is sent here)

5.friend node receives chat msg and also sends ack. to the poll

6. now the lpn sends the next poll not at 60th sec, but at 70th second(30 sec after prev poll with chat msg)

Is it an expected behaviour??

how to avoid sending poll message when sending normal mesh message???

RE: Exploring LPN features in mesh_light_switch example

Elfving — Wed, 18 Oct 2023 08:13:18 GMT

When it comes to this question about build time configurations:

LPN_RECV_DELAY: cannot be changed as it is part of the handshake to establish a friendship. The friend knows when to respond based on this value that is sent by LPN to FRND when friendship gets established. FRND keeps using this value through the friendship session.
POLL_TIMEOUT: Is also part of the friendship establishment procedure (as per spec) and cannot be changed in runtime. However, we have considered this possibility in stack, and provide an API to trigger polls much earlier if desired. It is "bt_mesh_lpn_poll()" API. Note that POLL_TIMEOUT is the maximum amount of time friend will wait until giving up the friendship. If LPN has enough power/energy available it can always send the poll earlier than POLL_TIMEOUT.
FRIEND_REQ_RETRY_TIMEOUT, REQ_RETRY_DURATION, LPN_AUTO_TIMEOUT: Could be made runtime configurable. This is something we can think of as an enhancement. Could you give me a detailed use case describing how making this runtime configurable would help your use case? I see that this can be useful feature in some situations, but I would like to know the use case.

Regards,

Elfving

RE: Exploring LPN features in mesh_light_switch example

Elfving — Tue, 17 Oct 2023 14:31:37 GMT

Sorry about the wait, things have been a bit busy here lately.

[quote user="mahesh vicky"]

Yes, that's what i meant. Either just after or before poll msg.

[/quote]

You could simply add this to the application if you want to. And if you could do it afterwards I'm not seeing why you couldn't do this on a custom model. Is this something you've considered? Could you expand a bit on what you would need to do?

[quote user="mahesh vicky"]And also the friend request retry timeout(BT_MESH_LPN_RETRY_TIMEOUT) has an max value of 3600(1 hr), can it be increased further?[/quote]

I believe so in theory, there doesn't seem to be a limitation there by the spec. I believe it is simply set to an hour, as you would likely prefer to do this manually if it takes longer than an hour. Not sure if it would be so straight forward to increase it though, as there could be limitations in our implementation of it, and this has not been tested.

Regards,

Elfving

RE: Exploring LPN features in mesh_light_switch example

Vignesh R — Tue, 10 Oct 2023 08:00:26 GMT

And the values like

LPN_RECV_DELAY,

FRIEND_REQ_RETRY_TIMEOUT,

POLL_TIMEOUT,

REQ_RETRY_DURATION,

LPN_AUTO_TIMEOUT

and etc.. in lpn.c file

are given as build-time configurable values, how can it all be set as user customizable at runtime??

Thanks

RE: Exploring LPN features in mesh_light_switch example

Vignesh R — Mon, 09 Oct 2023 11:54:35 GMT

[quote userid="103347" url="~/f/nordic-q-a/104418/exploring-lpn-features-in-mesh_light_switch-example/449158"]Could you expand a bit on what you mean by "along with"? Is afterwards okey?[/quote]

Yes, that's what i meant. Either just after or before poll msg.

And also the friend request retry timeout(BT_MESH_LPN_RETRY_TIMEOUT) has an max value of 3600(1 hr), can it be increased further??

RE: Exploring LPN features in mesh_light_switch example

Elfving — Fri, 06 Oct 2023 11:45:35 GMT

Hello,

[quote user=""]

so that i can execute my stuff(sending msg to friend and other processes) along with poll msg whenever it wakes up??

[/quote]

Could you expand a bit on what you mean by "along with"? Is afterwards okey?

Regards,

Elfving