Hi guys,
We are starting a fresh project these days. Let me try to describe our needs.
On one side, we should have a BLE module, as simple and small as possible, that will be used to send a simple message (once or few times per day) to the BLE central unit.
Central unit will be some nRF52840-based SoC module. There will be a few peripheral units (e.g. 3) and one central unit in the network.
It is quite important for us that the peripheral units are as small as possible and as low power as possible - we are gonna supply them with the coin cell batteries. The peripheral should also be compatible with nRF52840 SoC modules.
Do you, guys, have any small and sexy BLE module to recommend us? 
What kind of network would be optimal to implement in this use case where we have one central unit and a few peripheral units ? Communication is unidirectional - from peripheral unit to the central unit.
Should we implement a BLE mesh or to exchange the message in BLE advertisement mode or something else? Message should be kind of an ID of the BLE unit - like MAC address.
Thank you very much for your time and effort, guys! It is really appreciated.
Cheers,
Bojan.
