Synchronize boards about followifier

[suidpit]

I will need the help of anyone with the board to test this, but the functionality here is already laid out, we only need to glue the pieces.

[marcomicera]

I guess we'll first have to find out how much do boards get off sync with each other on average and then set a maximum desync threshold

[suidpit]

Update on this.

I have tested on my board this module by esp-idf. It works as expected.

After interaction with NTP server:

At this point, there's only to define when we should trigger the synchronization thread. I'd suppose we should leave the harsh decision to the main server (boards can be put to listen fore broadcast messages containing new time data), so that all the boards can sync at once.

We have a way to keep the boards in sync. We should test this at last, with more than one board connected to the main server.

[marcomicera]

I guess I'm the only one who can test this out as I have two boards. Do we have this feature already implemented somewhere in the code?

[suidpit]

Looking at the module linked, using the sntp module is really easy. The only issue here is decide where to keep this code working.
A basic idea would be to have a task which runs in the event loop, sleeps for a certain number of minutes, and then resynchronizes the clock.
Otherwise, if we want this to be handled by the server, we can have 2 sockets opened for each board:

• One for data, that is, the one we are using for the batches;
• One for control, where the server can send certain commands to the boards. One command would be encoded as "resynchronize", and when received, it would trigger the resync process.

[marcomicera]

I think this must be handled by the server. From the requirements:

Le stazioni di ascolto devono avere la stessa base dei tempi, così che le marche da esse apposte siano compatibili. A tale scopo, nelle fasi iniziali di avvio del sistema e periodicamente durante il suo funzionamento, devono scambiare dati con il PC volti a allineare i propri orologi ed a mantenere la sincronizzazione.

[suidpit]

What in this requirement makes you think that the sync process has to be handled by the server?
The server hosts the NTP server. That is the nature of the "data exchange" happening between boards and servers. The requirement doesn't state explicitly that the server must request the synchronization on demand.

[marcomicera]

Ops, yeah, I misread.

[suidpit]

Also, we don't need from the stations to be synchronizing at the same time, we only need them to have the same (with a given tolerance) timestamp. Therefore, I really think that a simple task that fires periodically and asks server for resync is what we're looking for.

[marcomicera]

Working on the sntp branch.