NRF5 Mesh: LPN polls Friend multiple times after message is published

[mesh777]

After LPN publishes message, NRF_MESH_EVT_LPN_FRIEND_POLL_COMPLETE event is generated five times. Also I noticed that instead of transmitting single publication message LPN sends it multiple times too (observed using nrf sniffer). I tried to change Network Transmit parameter in configuration server of LPN, but could not reduce the number of messages.

What could cause such behavior and how to disable automatic Friend polling after the message publication? LPN is set to publish to all Nodes and does that manually (without setting Publication period). Also Retransmission of publication is not set. Message is sensor server publication, sent unacknowledged.

I am using nRF5 Mesh SDK v5.

[Elfving]

Hello,

Could you tell me a bit more about the network, and if for instance the nodes and LPN are based on any example in particular?

Regards,

Elfving

[mesh777]

Hi Elfving. The network topology is pretty simple: LPN is connected to Friend node which acts as proxy too. Friend node is Nordic-DK with flashed light_switch server example. LPN firmware is partially derived from LPN example. LPN is set to sleep and it publishes sensor message on RTC (with a period of several minutes) or Button press. POLL_TIMEOUT_MS is set over 360min to avoid excessive friend polling. Friend is manually polled after publishing the sensor message.

I did not check yet if multiple messages/polling issue also occurs using LPN example project.

[Elfving]

I see.

Your issue looks a bit similar to this one, could you try what was suggested by Bjørn back then?

Regards,

Elfving

[mesh777]

Thanks for reply. I saw this thread before, and turned off proxy and rtt input as recommended. But still having multiple of friend poll complete events on the LPN. Is there a Mesh stack feature that sets LPN to poll Friend automatically after publishing message? If yes, would it be possible to disable it?

[Elfving]

Hello, sorry about the wait.

I assume that you are seeing it repeating 5 times as that is the default value of MESH_LPN_POLL_RETRY_COUNT. It tries to contact the friend 5 times, before regarding the friendship as terminated. 

I am not seeing this occurring in the SDK examples, only the standard polling that is happening routinely. I take it that the 5 repeating NRF_MESH_EVT_LPN_FRIEND_POLL_COMPLETE events you saw happened rather instantly / faster than the routinely happening one?

POLL_TIMEOUT_MS is just the timeout value, and doesn't control how often it is in fact occurring - only the maximum value. To set the interval, you can use mesh_lpn_poll_interval_set() in the LPN.

mesh777 said:

Is there a Mesh stack feature that sets LPN to poll Friend automatically after publishing message?

I believe it does, as the LPN is bound to already be available at that point. 

Regards,

Elfving