Hi all, sorry for being late to the party ... KNX is currently consuming all my cycles. Just wanted to add my thoughts to the discussion.
Initially I thought about adding this sort of information to the API, but then I thought that we have so little protocols supporting this sort of concept that blowing up every PLCValue with this time information just would waste CPU time and Memory. When it comes to simulating subscriptions by polling in the background, I thought it would be a valid solution to provide a default age a value can have in the cache and to make it possible to override this in the connection string options. If a value is too old, a return code of: STALE_DATA could be returned. Also, we do have an option of adding an additional set of PlcValue types. If a driver supports this quality-of-service type of data, we could return special versions of PlcValues, that have these properties? This way we don't have to waste the CPU time and Memory for protocols that don't support this concept (We could even implement the methods on the default PlvValues to simply return some constants to the PlcValues all have the same API. Chris -----Ursprüngliche Nachricht----- Von: Łukasz Dywicki <[email protected]> Gesendet: Montag, 8. März 2021 10:43 An: [email protected] Betreff: Re: Source Time of PLC Value? Looking at issue we could utilize marker interfaces. At least in Java we could define Qualified and Timestamped types. Yet looking at present state of API we are unlikely to make each and every PlcValue in each and every variant (qualified and timestamped, timestamped, qualified). It would force quite a lot of wrapping. Safest option I see is to extend subscription/response API with additional method to retrieve all markers. For most of drivers it would return just an empty set. It leaves us also an open door for future drivers (or devices) to ship additional piece of metadata which does not fit into present API. Best, Łukasz On 08.03.2021 04:30, Otto Fowler wrote: > So, maybe the extension is timestamp *and* timestamp source. > > uint64_t timestamp; > typedef enum { > /* timestamp was generated by the source device */ > SOURCE, > /* timestamp was generated by plc4x on receiving */ > GENERATED, > } TimestampQuality; > > > >> On Mar 5, 2021, at 18:04, Ben Hutcheson <[email protected]> wrote: >> >> We do have some error codes, but it would just need to be extended a >> bit. I don't think we have one for BAD (we still receive data but the >> source has marked it bad). >> >> Timestamps I think are definitely a good idea, especially if we >> eventually DNP3. >> >> On Fri, Mar 5, 2021 at 5:39 PM Łukasz Dywicki <[email protected]> wrote: >> >>> You have response code for each individual field which allows you to >>> determine state (OK, REMOTE_ERROR etc.). Same information should be >>> available also for subscriptions. >>> >>> Best, >>> Łukasz >>> >>> On 05.03.2021 21:04, Andreas Vogler wrote: >>>> Ah, forgot: and is there a status available? Valid/invalid/good/bad >>> indicator of a plc value? >>>> >>>>> On 05.03.2021, at 21:02, Andreas Vogler >>>>> <[email protected]> >>> wrote: >>>>> >>>>> Hi, >>>>> >>>>> How can I get the source time of a PlcValue? >>>>> >>>>> a) from a subscription PlcSubscriptionEvent >>>>> b) from a read request PlcReadResponse >>>>> >>>>> Best regards, >>>>> Andreas >>>> >>> >
