Basics of Point-to-Multipoint 433MHz wireless link?

[blapcb]

Hi. I would like to understand the basics of implementing a point-to-multipoint wireless link (in the 433MHz band).

The basic requirement is to have many nodes talk to a central PC via a single radio. The nodes collect data and need to communicate with the PC periodically. This would be a half-duplex link.

While I (think I) understand the basics of getting a single 1:1 link running, I would like to understand how to get several such wireless nodes talking to a single point.

I understand there are several chips out there that do basic Rx/Tx, but I am trying to understand the "division of responsibility" between the radio chip (or module) and the code running on the micro.

Thanks!

 

[RBB]

There's probably a lot of ways to do this.

The nodes can transmit their data given some type of "broadcast address" in the header, and then have some unique id in the payload.

This would allow the PC station to receive data from all nodes, because it is keying off the broadcast address, and it can also determine which node sent the data via the unique id in the payload.

 

[blapcb]

Thanks RBB. What I meant was more in terms of, say, should this use a single frequency of multiple frequencies, ASK, FSK or OOK (for example), and how do you "schedule" the various devices talking to the PC radio (there must be some type of scheduling mechanism, or do they listen for a clear channel and try? but then what if two try and the same time? and re-try at the same time?).

hmmmm.....