Calculating duty cycle only using advertisements

[StevenG]

Hi!

I'm close to finishing a project where every type of messaging is done using simple BLE broadcasts (using my own frequency hopping and other features.)

However I still need to calculate the period where devices are allowed to broadcast.

Since I'm aiming towards low power use, a 1% duty cycle is preferred.

Using the nRF Online Power Profiler I've found that a SINGLE non-conn adv takes about 376microseconds. (31 byte payload, 1Mbps, 5% )

However, my question is aimed towards extra overhead:

Do I, for example add the 'Radio Start' period into the duty cycle?

Does this mean some kind of preamble or extra overhead I should worry about?

Or should I do the obvious 376microseconds, times 100, as an average period between data packets for a 1% duty cycle?

Thanks in advance

Steven

[Joakim Jakobsen]

Hi Steven.

Sorry about the late response.

I don't think you should add the "radio start period", but I will double check this for you.

Let me get back to you with more information.

Br,
Joakim

[StevenG]

Any update :D?

I'm still not sure about the 376microseconds times 100, since this feels like a super low interval to broadcast messages.

Because let's say I have five connected devices to a central gateway, each broadcasting in its own timeslot. This means an average slot would be like 400 microseconds. This feels SUPER tight, as I'm working in the realm of 10's of milliseconds accuracy. 

Any tips?

[Joakim Jakobsen]

Hi.

Some delayed feedback on this.

You shouldn't need to manually add the "Radio start period" as this is included and handled by the SD.