about broadcast (nrf52840, sdk15.0)

[lmouelo]

hello, i have a question about broadcast mode : 

can the broadcast mode be used in parallel with the ble mode? 

thank you.

[lmouelo]

what  is this time between each sends on the different peripherals?

it's always the same time ?

[Edvin]

The time between each communication event between the master/central and the slave/peripheral is called the connection interval. It is typically set near the top of the main.c file in our examples. The defines are:

MIN_CONN_INTERVAL

MAX_CONN_INTERVAL

and are given in units of 1.25 ms.

If you control both devices, central and peripheral, you can set MIN_CONN_INTERVAL = MAX_CONN_INTERVAL, and also equal in both of the devices. (The devices will disconnect if they can't agree on a connection interval).

 

The minimum allowed connection interval in BLE is 7.5ms ( = 4 units of 1.25ms).

I am not sure whether you will be able to squeeze 4 connections with a connection interval of 7.5ms on one central, but you can give it a go. 10ms should be fine I believe. Do some testing, and you will figure out pretty fast whether the connections will be maintained or not.

 

So a standard broadcast message is not possible in BLE. You can look into using the esb examples that we have, where several devices can listen on the same channel, and hence you can do broadcasting with this. Check out the examples:

SDK\examples\proprietary_rf\esb_prx

SDK\examples\proprietary_rf\esb_ptx

if you are interrested.

 

Best regards,

Edvin

[lmouelo]

 ok thanks you and so to send exactly at the same time (broadcast) I can't use ble, I have to use the role of radio ?

[Edvin]

That is correct. To send exactly at the same time, you must use some proprietary radio protocol, such as the esb examples (which is a different protocol than BLE).

The disadvantage with this is that the esb devices has to be listening at the time when you are transmitting. This is possible, but it takes a lot more current than using BLE, because they have to have the radios on the entire time. That does not mean that you can't do it, but if the device runs on a battery, it will be drained faster.

 

Best regards,

Edvin