Best solution to BLE-enabled device as central and peripheral?

[Ross Llewallyn]

After seeing a few answers here (and elsewhere) which were very helpful to understanding the scope of my problem:

devzone.nordicsemi.com/.../ forums.adafruit.com/viewtopic.php devzone.nordicsemi.com/.../

...I'm curious if anyone has suggestions for an optimal solution to a design I'm working on.

We have a smart watch that will report heart rate, for example, so we designed the device to be a peripheral communicating with a hub (central) that collects data. It is using the nRF8001.

But we also want the watch to be able to receive notifications from the user's phone. This means, I think, that the watch should be the central and the phone the peripheral.

In the third link I shared, the nRF51822 chip is mentioned that can serve both roles. What are the costs of using it compared to using the nRF8001 we currently have?

How distinct do these modes (central versus peripheral) have to be? Can they work seamlessly together or need to be set as only one or the other?

We have been hypothesizing methods to misuse the BLE standard to transmit data from central to peripheral. Surely, since this has been implemented in so many commercial devices, there is an elegant solution, but I don't know the proper path.

I'd appreciate any thoughts or answers.

[James Yu]

So if I understand correctly you have a smart watch that you want to communicate with a mobile phone.

In this case it is sufficient for the smartwatch to be the peripheral and the phone to be the central all the time. The smartwatch can send notifications to the phone, and the phone can read and write to the smartwatch.

Notifications from the phone can be achieved using writes, so there is really no need to reverse the roles.