[Xastir-dev] LORA and interfacing

Sat Jul 31 13:38:05 PDT 2021

I’ve noticed that the KISS implementation on a lot of these devices is a
forked over version of the Rnode. He used the Sx 1276 chip as well because
it has really good RX sensitivity at the lower rates. He also has a newer
and easier form of KiSSattach.
https://github.com/markqvist/tncattach

I like your thoughts about changing modulation on the fly. I’ve seen it
done with higher level stuff , Ubiquiti and others.  Just wonder how much
it would slow things down. Cause I think you would do that per packet.
Maybe per connection.

Right now I’m just interested in tying a few of the different versions and
seeing what works. No real goals in mind, just checking it out and
experimenting.

I’ve thought about a repeater, but that would kill the great RX sensitivity
, but a digi would be good. A old style repeater separated by distance and
a link would work.

Might even try Winlink on it and see what what happens when I stir that pot!

So many ideas.

Steve N0FPF

On Sat, Jul 31, 2021 at 12:58 PM Kristoff <kristoff at skypro.be> wrote:

> Steve,
>
>
> I also have this model:
>
> https://www.amazon.nl/DollaTek-LoRa32-SD-kaart-draadloze-module/dp/B07RXSKPBX/
>
> The disadvantage is that it lacks the 8 Mbit PSRAM chip (which is on the
> T-beam) so the ESP32 is a bit short on memory for embedded python. (less
> then 1 MByte of RAM available).
>
>
> Software development-wize, perhaps it makes more sense to turn the
> radio-device into just a dumb 'packet-modem', connect it to a
> single-board computer (say, a raspberry pi) and do all development
> overthere. That way you can run higher-level code, easily interface with
> the internet, connect other devices (e.g. a VHF/UHF packet mode), etc.
>
> Last week, I found this python module for processing aprs message (*)
> which I think would be a good basis to do some experimental development
> for aprs-code.
>
>
>
>
> I do like the sx1276 chip. It has a couple of nice features.
>
> - as it also has a FSK modem, It might also be able to transmit POCSAG
> (paging) messages. If this works, we should be able to build a
> APRS-to-POCSAG gateway with just one piece of hardware: send a aprs
> text-message to a certain APRS node and it transmit that message as a
> POCSAG paging message.
>
> I once wrote some code to create pocsag-message. (**)
>
>
> - The automatic header-detection in lora is nice,
> This means that if you send a packet with (say) a coding-rate of 4/8 to
> a lora-node configured with 4/5, the chip will still receive and decode it.
>
> So, if you know that you are in area with bad APRS-over-lora coverage,
> you can switch to a coding-rate that provides better error-correction
> (like 4/8). Your packets will become larger (by 37.5 % in this case) but
> your packet might still arrive, which it might not have done with a
> coding-rate of 4/5.
>
> Note that that bandwidth and Spread-Factor do need to match. If not,
> your packet will not be demodulated/decoded.
>
> - Another nice thing is that, although the chip does have CRC-generation
> and CRC validation in silicon, it will still pass packets to the
> receiver, even if they fail the CRC check.
> It will flag it as 'CRC error', but the code on application-level will
> still be able to retrieve it.
> Most other radio-chips I have looked at so far do have do not do this
> and will silently drop that message.
>
> This would allow for a nice lora "DX-ing" mode by implementing
> additional error-correction code on application-level.
>
>
>
>
> Ah yes, there is also a GNU Radio implementation of the Lora PHY. (***)
> I haven't tried it yet, so I do not know if it works but It would be
> interesting to experiment with this, e.g. tweaking the parameters even
> further to do even further DX.
>
>
>
> I am not on Facebook.
>
> I prefer mailing-lists for in-depth discussions. To get real-time help,
> ...  I am on matrix / element.io which is an open-source and
> decentralized IM/voice/video service.
> There are quite some open-source groups reachable via matrix, either
> directly on matrix itself or via bridges to IRC or some other IM protocol.
>
> It's used the GNU Radio community.
>
>
> (*) https://github.com/ampledata/aprs
> (**) https://github.com/on1arf/pocsag
> (***) https://www.epfl.ch/labs/tcl/resources-and-sw/lora-phy/
>
>
> 73
> kristoff - on1arf
>
>
> On 31.07.21 20:31, Steve wrote:
> > I gave two of the TTGO units including a couple of Rnodes.
> >
> > I’m going to try a couple of the existing firmware options out there.
> Some
> > are KISS based some are not. I like the possibility of using the wifi or
> > Bluetooth with the TTGO with some of the APRS programs fir the phones.
> >
> > Seems for a mobile device, not have a extra board such as a PI might be
> > nice… we’ll see!
> >
> > The TTGO can also be used for this:
> > https://tinygs.com
> >
> > The Rnode guy is also implementing a MESH system but is only in the alpha
> > stage. Beyond my ability.
> >
> > I’ll have to get back to you on Freq, I only got my TTGO going last night
> > and didn’t bother to look!
> >
> > There is a LORA APRS group on Facebook, grin, that is mostly from Europe
> > who have a lot of experience with this .
> >
> > Steve N0FPF
> >
> >
> >
> > On Sat, Jul 31, 2021 at 11:20 AM Kristoff <kristoff at skypro.be> wrote:
> >
> >> Steve,
> >>
> >>
> >> Your project interests me too.
> >>
> >> We are using this hardware:
> >> https://github.com/LilyGO/TTGO-T-Beam
> >>
> >> We are on 433.775 MHz, 150 KHz, SF12, 4/5
> >> What frequency and what mode do you use?
> >>
> >>
> >> The software comes from this project:
> >> https://github.com/lora-aprs
> >> But if the code of your project is standard arduino, it shouldn't be to
> >> difficult to port it to ESP32.
> >>
> >> Apparently, there are also some high-altitude balloon projects that use
> >> lora for their telemetry download.
> >>
> >>
> >>
> >> My personal interest is to use this for doing some software
> >> experimentation, so I use micropython on the ESP32 (fast development)
> >> and not the arduino code.
> >>
> >>
> >>
> >> 73
> >> Kristoff - on1arf
> >>
> >>
> >>
> >>
> >> On 31.07.21 20:05, Steve wrote:
> >>> I connected it to my 10 db Omni antenna at home right at the base to
> >>> minimize the loss.
> >>>
> >>> I was impressed that it was heard around some of the hills in west
> >> seattle .
> >>> I have plans to put a IGate at a high point around the end of the
> summer.
> >>>
> >>> I also found a small bi- directional amp too.  Boost it to a watt or
> two.
> >>> Just don’t want to kill the receive sensitivity. Around $60.
> >>>
> >>> It’s all in the antenna.
> >>>
> >>> Steve N0FPF
> >>>
> >>>
> >>> On Sat, Jul 31, 2021 at 10:59 AM Tom Russo <russo at bogodyn.org> wrote:
> >>>
> >>>> On Sat, Jul 31, 2021 at 10:35:44AM -0700, we recorded a
> bogon-computron
> >>>> collision of the <stevewa206 at gmail.com> flavor, containing:
> >>>>> I have interfaced the Rnode Lora device. It does Kiss and used a PI
> 3.
> >>>>> Pretty straight forward.
> >>>>>
> >>>>> https://unsigned.io/projects/rnode/
> >>>>>
> >>>>> I was able to do a client and a IGAte.
> >>>> That is pretty cool!
> >>>>
> >>>> --
> >>>> Tom Russo    KM5VY
> >>>> Tijeras, NM
> >>>>
> >>>>    echo "prpv_a'rfg_cnf_har_cvcr" | sed -e 's/_/ /g' | tr [a-m][n-z]
> >>>> [n-z][a-m]
> >>>>
> >>>> _______________________________________________
> >>>> Xastir-dev mailing list
> >>>> Xastir-dev at lists.xastir.org
> >>>> http://xastir.org/mailman/listinfo/xastir-dev
> >>>>
> >> _______________________________________________
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> >>
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-- 
Pardon the brevity, sent from a mobile device. So there.