Best starting point to minimize BLE delays

Is the scenario described above feasible?  

>>Yes, technically, this scheme is possible but why do you want both devices to be peripherals? Why not have these two devices be a Central and a Peripheral, respectively, and remain connected (with a connection interval < 300ms). 

If so, should I use a standard profile or a proprietary profile? Is there a performance penalty using one of these compared to another? 

>> You can do with with a proprietary profile made up of a couple of custom characteristics to carry the button press and sensor information. 

Is there a good example program to start with that would minimize the new code development required?

>> The P2PServer/Client example is probably the best example you can start with. This example implements a couple of custom characteristics to carry button control and LED information. The custom characteristics are defined in P2PS_STM_Init() routine, so you can customize these characteristics for your needs. Then you can see how the button data is sent to the remote device by updating the characteristic in P2PS_Send_Notification(). 

I have played with the BLE_p2pServer and BLE_p2pClient programs on the WB55 Nucleo boards. I'm seeing a connection time of 10-12 seconds using this code, although much of this appears to be in the discovery phase. Is this typical for establishing a connection between 2 devices? What can I do to reduce this time?

>> I have noticed that the discovery phase and connection can be lengthy, this is why I suggested to consider keeping your two devices connected. I'm checking if something could be done to reduce this time. 

Hi Joe - thanks for the quick response!

The reason I don't want one device to always be a central is that there is another use case involved here that I did not describe. There may be a phone that needs to talk to both devices as well. In this case, I want the devices to be peripherals and the phone to be central. But there are cases where the phone is not involved, and the devices need to communicate with each other. This is why I was thinking that the device would need to switch roles from peripheral to central if its' button is pressed. Is there an example or a description of the steps to take to switch roles like this? How hard would it be to modify either the p2pClient or p2pServer examples to also handle the other role - something like switching roles on a button press?

I do not want to leave the devices connected at all times, as this would drain my battery too quickly. I'm hoping to go into a low power mode when the devices are idle.

Does pairing the devices help to reduce any of the discovery time? Each device will ever only be communicating with one other device.

Thanks...

Brian

​Hi Brian,

You can look at the BLE_p2pRouteur example, which demonstrates the capability to connect to a master and multiple slaves on the same device, so this device is able to advertise as a peripheral and scan as a master for peripherals.  You can tailor this example as you wish to advertise or scan when desired (button press).

Regards