There are standard query messages defined in APRS. The ones directed to a specific station (as opposed to broadcast to every APRS station within RF distance) are sent as APRS text messages addressed to the target station, with a text body starting with a question mark. The standard queries include (but are not limited to):
?APRSD - report the stations directly heard (not via digipeater) by the target station
?APRSM - resend all the APRS text messages currently outstanding by the target station and not acked by their recipients
?APRSO - resend all APRS Objects and Items transmitted by the target station
?APRSP - transmit the target station's current position report immediately
?APRSS - transmit the target station's current status message immediately
?APRST - transmit a response to the querying station so they know the digipeat path taken to reach the target station
Some APRS software support additional non-standard queries. YAAC's full list of supported queries is in the built-in help. And most of the standard queries can be sent in YAAC from the Query menu.
However, there isn't a standard query to force extra transmissions of APRS telemetry messages (or any other kind of traffic). And not all stations support all query messages (in particular, transmit-only trackers don't support any queries at all, since they don't listen for traffic).
I have worked on a telecommand plugin for YAAC, so it could respond to non-standard queries. But I haven't released it because I haven't come up with a generic way to map queries to data collection actions. I have released a draft of my RV telemetry plugin for YAAC (which doesn't have to be used solely in recreational vehicles, but does have features peculiar to mobile station needs), but that plugin only provides a way to send standard APRS telemetry messages asynchronously (though it does implement a non-standard query ?TELEM to force immediate standard telemetry message transmission).
So, if you want to query synchronously for some information on a station (rather than passively listening for asynchronous posts by the data originating station), you will have to have custom software to listen for your custom query message and respond appropriately to it.
Andrew, KA2DDO
author of YAAC
________________________________________
From:
[email protected] <
[email protected]> on behalf of Michael WA7SKG <wa7skg@...>
Sent: Saturday, October 14, 2023 11:18 PM
I understand there supposedly is a method within APRS to send a query to
a station and get a response, like for sensors, send a request and get a
message back with a value. This would be to measure a voltage,
temperature, level, switch position, status, etc. This is as opposed to
just having it send a regular telemetry string on a regular basis, I guess.
Could somebody please explain to me more how this works or point me to a
tutorial or document or something? Is this something I can do with YAAC,
or does it require another application?
--
73,
Michael WA7SKG
"Any day you do not learn one new thing is a wasted day."
Michael WA7SKG