Which SDH Dispatch mode should I use?

RE: Which SDH Dispatch mode should I use?

Hung Bui — Mon, 16 Oct 2017 13:33:43 GMT

I see, I would suggest to pull the events out using ISR, but offload the time consuming tasks in to main loop using app scheduler for example.

RE: Which SDH Dispatch mode should I use?

Marius Heil — Fri, 13 Oct 2017 15:15:48 GMT

Thanks, I am considering switching to interrupt mode. But I think this will result in NACKing as well if my ISR takes too long and the Softdevice buffer gets filled up.

RE: Which SDH Dispatch mode should I use?

Hung Bui — Fri, 13 Oct 2017 08:42:04 GMT

Ok, I was thinking you want to compare the softdevice handler module from SDK v13 vs SDH in SDK v14.

The draw back of polling is that if you don't poll the event from the softdevice quick enough and if the event buffer is full, the softdevice will start NACKing the peer device when there is a data/command packet. This might result in connection termination if the peer device set a timeout.

RE: Which SDH Dispatch mode should I use?

Marius Heil — Fri, 13 Oct 2017 08:05:41 GMT

Thanks, I know that I can keep my old polling code when rewriting it a little. But I want to know what the pros and cons between polling and interrupt mode are. E.g. what happens if I block the Softdevice event interrupt for a long time, etc,...

RE: Which SDH Dispatch mode should I use?

Hung Bui — Thu, 12 Oct 2017 10:53:09 GMT

Hi Marius,

I assume you modified the softdevice_handler in the older SDK so that instead of pulling the event out on SWI2 interrupt it will fetch the event though a loop and poll?

The mechanism wasn't change with SDK v14. You still can modify that to your customized one, inside nrf_sdh.c

What we introduced in SDK v14 with the SDH library was (according to release note):

- SoftDevice Handler:
    - Can now register 'state event observers' that are notified when the SoftDevice state changes.
    - Can now register 'request event observers' that are notified when a change of the SoftDevice state is requested.

In addition, as stated in the doc, you can choose different priorities for different Observers, so you can control the order of the observer handlers when there is an event.