> No, I am saying that I think WeeWX is already creating APRS weather > frames that get carried in AX.25, and that both over-the-air and CWOP > use this format
That would be ideal, if the heavy lifting is already being done. > I am a bit fuzzy on details, but I think you have a > situation where you have a device (TNC) that wants to read $ULTW format > and translate that to APRS format and then put that string in an AX.25 > frame and modulate it over radio. Yes, that is essentially it. Traditionally, it was this: WX Station ($ULTW format in serial TTL or RS232) > TNC or APRS Specific Modem Device > VHF Radio (Transmits 1200 baud AX.25 over the air) > I am wondering if you could use the TNC in KISS mode and have weewx > generate the AX.25 frame content, by modifying the CWOP transmitter, > and skip ULTW. I mentioned in a previous message that I am NOT a good code guy. I hack my way through things. I'm a hardware guy. However, years ago I did mange to write some ok working KISS routines in Visual Basic. I learned A LOT about the AX.25 frame structure and adding the KISS wrapper to the frames. Basically, it's an AX.25 frame with <C0> tags on each end to show the start and end of the frame. The destination and source call, as well as the path are all encoded in a bit shifted format. The payload it's self is not changed and can be human read without any translation. If you look at a KISS AX.25 frame in a terminal, it looks like garbage until it gets the PID character and then you can read the payload. In this case, it would be the $UTLW string in HEX. <C0><destination><source><path><PID>:<payload><C0> If we can produce these frames with the $ULTW payload already inserted and then just feed that directly to the TNC over USB, that would be ideal and I can tell you a lot of APRS guys wanting to run a WX station on APRS would use this feature. There was an APRS specific WX station years ago that did just this. Even had the TNC/modem built in. Just hook up sensors and a radio and you were on the air. I think it was uWeather or something like that. Jason K4APR On Wednesday, August 31, 2022 at 8:57:22 AM UTC-4 Greg Troxel wrote: > > "[email protected]" <[email protected]> writes: > > >> Your comment is hugely helpful; it points out that formatting is already > >> done. But that's fully-baked APRS format, not format to be read by a > >> device that translates Ultimeter to APRS. Maybe that would help the OP > >> though as it may be possible to send AX.25 frames instead? > > > > Are you saying that WeeWX is already creating AX.25 frames with the > $UTLW > > format? If so and it's KISS, then that's exactly what I need to feed to > a > > TNC for the station. In a perfect world, that's exactly what I would > > need. WeeWX brings in the data from the AcuRite, formats it to $UTLW, > > builds the KISS AX.25 frame and spits it out either via USB (/ttyAMA0 or > > whatever) or through the UART pins to a serial interface. > > No, I am saying that I think WeeWX is already creating APRS weather > frames that get carried in AX.25, and that both over-the-air and CWOP > use this format. I am a bit fuzzy on details, but I think you have a > situation where you have a device (TNC) that wants to read $ULTW format > and translate that to APRS format and then put that string in an AX.25 > frame and modulate it over radio. > > I am wondering if you could use the TNC in KISS mode and have weewx > generate the AX.25 frame content, by modifying the CWOP transmitter, > and skip ULTW. > -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/weewx-user/433fd993-87fa-483b-91f8-bfd160b30f3an%40googlegroups.com.
