Any Downlink metadata at the node?

[DashCanTtn]

Is there any “metadata” attached to downlink messages at the node?

eg, any time information?

[descartes (Nick McCloud)]

No. But there is a MAC command to get the time.

Please search the forum for discussions about a node being aware of time - particularly in relation to the number of decimal places, synchronising and time stamping of uplinks.

[DashCanTtn]

@descartes

there is a MAC command to get the time

So DeviceTimeReq ?

Lots of posts asking if it’s supported: many saying no, but that seems to be for V2; V3 does now support.

And some bedtime reading on Application Layer Clock Synchronization:

Clock synchronization

As mentioned here: TTN doesn’t support DeviceTimeReq. So, to sync time I should use Application Layer Clock Synchronization as here: How do I sync time for test purposes? Is there some “magic button” on TTN console to sync time via AppLayer or maybe some cloud-based app, which I can connect to my console to sync tme or something. I just don’t want to write time synchronization server app for myself.

EDIT

Ah, it says anything with access to the DeviceTimeReq MAC command SHOULD use it instead of the Application Layer Clock Synchronization.

[DashCanTtn]

@descartes

No

Is that no metadata at all, or just “no” to the time example?

[descartes (Nick McCloud)]

That’s a no to all unless you count any MAC commands that may piggy back on the payload but they aren’t meta-data, they are commands.

The radio chip can report the RSSI & SNR but that’s not in the payload.

You could look at what comes down the wire in the LoRaWAN spec …

[cslorabox]

@DashCanTtn

any time information?

A more productive discussion would be to explain the purpose of the node wanting to know time, as that could get into viable vs non-viable ways of doing so, and possible complications of the reason for wanting to do so (for example, highly deterministic transmit timing is a mistake since it can lead to repeating on-air collisions - take the measurements at precise times if you want, but transmission should be a bit drifty/random in timing)