Star Topology Duplex Commuication

[Break Stuff]

Are they any units capable of a 4 way network where every message is broadcast to the whole network? Preferably, with UART.

[endnode]

Assuming you are interested in BLE not 2.4GHz radio in general then yes, both nRF51 and nRF52 chips with the latest Soft Devices (Nordic BLE sack) are capable of 4 or more GAP Central duplex connections at the same time so they can serve as center of such "star". This is actually feater introduced already in BT SIG 4.0 spec 7 years ago so basically all today's BLE chips and stacks support this. Just remember that there is nothing like "broadcast" in connection based BT LE stack, all connections (now not speaking about latest BT mesh or proprietary solutions) are peer-to-peer. So if you want to distribute some message to all "leafs" of your "star" you will need to send it one by one over all links and they won't happen at the same time. However with custom HW+stack you should be able to run 4 connections with 15ms interval (or maybe even lower) so in 15ms you will update all devices in your star (if communicating "leaf" to "leaf" then it doubles).