Supporting a real-time task

[Bret Foreman]

My 51822 needs to support some realtime control code that runs for about 75mS. During that time I need to mask all interrupts. With a logic analyzer I can see that my realtime code is getting interrupted every 25mS or so, I guess by the SoftDevice. I tried using CRITICAL_REGION_ENTER/CRITICAL_REGION_EXIT but that does not mask the interrupts.

1. How can I mask interrupts so that my realtme code will not be interrupted no matter what the radio is doing?
2. Is there a way to do this such that I don't unduly disturb the SoftDevice?

Regards, Bret

[Audun]

Hi Bret,

in that case, you need to drop the connection or stop advertising. There are no mechanisms to forcibly skip radio events as far as I know.

Stopping advertising is an immediate action, however there is a corner-case when a connection request is received at the same time as advertising is stopped. Doing a proper disconnect will take more than a couple of ms, so that's not an option. The only way to immediately halt all radio activity is to disable the softdevice using sd_softdevice_disable(). Note that the Central will consider the link active until the Supervision Timeout has expired, and will typically not attempt to reconnect until that happens.

[Bret Foreman]

Audun,

I just tried the approach where I stop advertising during my r/t task (by calling sd_ble_gap_adv_stop). I see a connection timeout in the MCP when I do this. And then when I start advertising again my application hangs. I suspect this is because the connection is now stale in the SoftDevice and restarting advertising on a stale connection corrupts the SoftDevice.

I'm not seeing any BLE events from the SoftDevice when the connection timeout occurs so I guess I need to make some sort of API call to see if the connection is stale and then re-establish the connection before I can resume advertising. Can you give me more details about how I might do that?

Thanks, Bret