Not possible to re-start advertising

[muli]

With the latest SDK 2.6.0, I am developing from the existing NRF5340 audio application for a receiver, to allow an ACL connection from a mobile app. Advertising starts fine, connection gets established from the central app without issues. 

The problem I am having is that when the app manually disconnects itself from the receiver, advertising tries to start again, but can not with the following issue : 

<err> bt_mgmt_adv: Failed to start advertising set. Err: -12

This means not enough core. 

I have tried to resolve this by calling bt_le_ext_adv_stop() and even bt_le_ext_adv_delete() in bt_mgmt_adv_start() before bt_le_ext_adv_create() gets called. This didn't solve it.

I have also tried to solve it by calling bt_le_ext_adv_stop() right before bt_le_ext_adv_start() inside advertising_process().

The same -12 error occurs no matter what. Everything else inside advertising_process() executes without an error , and only bt_le_ext_adv_start() fails. 

At this stage i'm not sure if it's an issue with the SDK or I am doing something wrong. Thanks in advance for any support. 

[ovrebekk]

Hi Paul

Where in the code do you try to restart advertising? 

It is not possible to restart advertising directly in the disconnected callback, as this callback is running in interrupt context. If this is what you are doing, could you try to schedule the advertising start functionality using a work item instead? 

Best regards
Torbjørn

[muli]

Hi ovrebekk 

Thanks for your reply.

This is strange. If you look at disconnected_cb() in bt_mgmt.c, it is already implemented there from Nordic, to start advertising by calling bt_mgmt_adv_start() 

[Jared]

Hi Paul,

We're currently short on staff due to the Easter Holiday,

You can expect an answer sometime next week,

Thank you for your patience,

regards

Jared 

[ovrebekk]

Hi Paul

Sorry for the slow response. Are you still having issues with this? 

muli said:

If you look at disconnected_cb() in bt_mgmt.c, it is already implemented there from Nordic, to start advertising by calling bt_mgmt_adv_start() 

You are correct of course. 

bt_mgmt_adv_start(..) will only start advertising indirectly, by submitting to the adv_work work item which in turn will call the advertising_process(..) function from the system workqueue. 

As such you should be able to call this function either from interrupt or thread context. 

Do you know what the BT_MAX_CONN configuration is set to in your application? 

Could you try to add a breakpoint on this line and see if this is where the -12 (ENOMEM) error originates? 

If that is the case I am wondering if the issue is that the connection is not yet freed up, and as such you get a ENOMEM error when trying to restart the advertising. 

Best regards
Torbjørn

[muli]

Hi ovrebekk 

This is very interesting actually:) 

I set the BT_MAX_CONN to 4 in my proj.conf file. 

Now I can disconnect and reconnect 4 times until I get an ENOMEM on that line you mentioned. 

So clearly the connection isn't getting cleared up as expected each time. 

Update : I wasn't un-referencing the connection in the disconnected callback.

Problem solved. Thank you.  

[ovrebekk]

Hi Paul 

Very good to hear that you found the issue. I will close the ticket then

Best regards
Torbjørn