5 ms·

FreakWAN: A floor-routing WAN implementing a chat over bare-LoRa (no LoRaWAN)

56 points by teleforce 1y ago

exabrial 1y ago
> Simple home-made driver for the SX1276 and SX1262 LoRa chip Beware of what nailed the Meshtastic people: These chips don't have temperature dependent crystal oscillators. Transmitting more than a few milliseconds causing a temperature rise, throwing the clock off, causing transmission warpage, causing timing errors, causing transmission failures.
- Neywiny 1y ago
  You mean they don't have temperature compensated? What you described is temperature dependent
  - exabrial 1y ago
    too late to edit now :)
- bigfatkitten 1y ago
  This is a radio module issue, not a chip issue. Cheap modules have cheap crystals, better ones have a TCXO.
- ShakataGaNai 1y ago
  Temperature Compensated Crystal Oscillators (TCXOs) is what they should be looking for. And to be clear you can get SX1262 variants with such, eg: https://wiki.seeedstudio.com/wio_sx1262/ https://wiki.seeedstudio.com/wio_sx1262/ For the detailed run down, see https://cdn.sparkfun.com/assets/f/f/b/4/2/SX1262_AN-Recommendations_for_Best_Performance.pdf https://cdn.sparkfun.com/assets/f/f/b/4/2/SX1262_AN-Recommen... page 14 > In the case of an SX1262 operating at +22 dBm in the US 902 – 928 MHz band, the frequency drift measured during the maximum LoRAWAN™ packet duration stays below the maximum limit, provided thermal insulation is implemented around the crystal during PCB design. > At extreme temperatures (below -20 °C and above 70 °C), it is recommended to use a TCXO. > For any other frequency bands corresponding to longer RF packet transmissions at +22 dBm, it is recommended to use a TCXO.
  - buckle8017 1y ago
    Theory and reality are different here. As used in the meshtastic devices this chip does actually fail doing normal Lora transmission under reasonable conditions. I know because I've seen the exact failure.
    - nerdsniper 1y ago
      You've seen the failures in variants with a TCXO?
- oakwhiz 1y ago
  The chip itself supports using a TCXO instead of a regular crystal
LelouBil 1y ago
I tried doing something like this on an ESP32 last year, I wanted to understand how to do an actual mesh with devices that can't transmit and receive at the same time, but I didn't find documentation. I managed to get 2 devices communicating across town at least ! (After having antenna issues)
mytailorisrich 1y ago
Previously [2023]: https://news.ycombinator.com/item?id=35882967 https://news.ycombinator.com/item?id=35882967
embedding-shape 1y ago
Chat/text over LoRa always sounded intriguing! I'm merely a 1000km away from Sicily (which antirez say they wanna cover with the network at first), I wonder if it would be possible to do what AM radio does, bounce against the ionosphere and get huge ranges for transmission? Maybe it would need way too much transmission power? Maybe hopping all the way P2P style makes more sense, although surely would be slower.
- bigfatkitten 1y ago
  Not at 900MHz. Skywave propagation mode is only available under about 30MHz. Above that, the signal reliably continues on into space. At frequencies this high, you’re realistically limited to near line of sight paths.
  - embedding-shape 1y ago
    > Not at 900MHz Shame, but at least now I understand why, thanks :) > you’re realistically limited to near line of sight paths Wonder exactly how far one would be able to get up to reach 1,000km line of sight, assuming you put both points equally far up. Guessing it's the curvature of the earth that gets in the way at that distance?
    - bigfatkitten 1y ago
      Yep. There are cubesats running LoRa payloads in low earth orbit[0], and between mountaintops, terrestrial paths of hundreds of km are possible[1]. [0] https://www.hackster.io/news/fossasat-1-an-open-source-satellite-for-the-internet-of-things-7f31cab00ef5 https://www.hackster.io/news/fossasat-1-an-open-source-satel... [1] https://meshtastic.org/docs/overview/range-tests/ https://meshtastic.org/docs/overview/range-tests/
      - embedding-shape 1y ago
        > Using metal tape measures to build simple quarter-wave monopole antennas is a hack to that’s actually pretty common in the small satellite community This is just too crazy, thanks a lot for sharing these links! :)
mdhb 1y ago
I think there’s some real value in WANs that are independent of both the internet and existing telco infrastructure but I don’t think I would put a specific transport at the centre of its design. I think you would be much better off with something like bundle protocol v7 and delay tolerant networking as the actual centrepiece and have something like LoRa as one of many transport link options. Maybe we are talking about a different threat model here but LoRa as the centrepiece falls apart really quickly the moment someone somewhere decides they don’t want your WAN to exist anymore.

56 points by teleforce 1y ago

> Simple home-made driver for the SX1276 and SX1262 LoRa chip Beware of what nailed the Meshtastic people: These chips don't have temperature dependent crystal oscillators. Transmitting more than a few milliseconds causing a temperature rise, throwing the clock off, causing transmission warpage, causing timing errors, causing transmission failures.

Neywiny 1y ago
You mean they don't have temperature compensated? What you described is temperature dependent
- exabrial 1y ago
  too late to edit now :)
bigfatkitten 1y ago
This is a radio module issue, not a chip issue. Cheap modules have cheap crystals, better ones have a TCXO.
ShakataGaNai 1y ago
Temperature Compensated Crystal Oscillators (TCXOs) is what they should be looking for. And to be clear you can get SX1262 variants with such, eg: https://wiki.seeedstudio.com/wio_sx1262/ https://wiki.seeedstudio.com/wio_sx1262/ For the detailed run down, see https://cdn.sparkfun.com/assets/f/f/b/4/2/SX1262_AN-Recommendations_for_Best_Performance.pdf https://cdn.sparkfun.com/assets/f/f/b/4/2/SX1262_AN-Recommen... page 14 > In the case of an SX1262 operating at +22 dBm in the US 902 – 928 MHz band, the frequency drift measured during the maximum LoRAWAN™ packet duration stays below the maximum limit, provided thermal insulation is implemented around the crystal during PCB design. > At extreme temperatures (below -20 °C and above 70 °C), it is recommended to use a TCXO. > For any other frequency bands corresponding to longer RF packet transmissions at +22 dBm, it is recommended to use a TCXO.
- buckle8017 1y ago
  Theory and reality are different here. As used in the meshtastic devices this chip does actually fail doing normal Lora transmission under reasonable conditions. I know because I've seen the exact failure.
  - nerdsniper 1y ago
    You've seen the failures in variants with a TCXO?
oakwhiz 1y ago
The chip itself supports using a TCXO instead of a regular crystal

LelouBil 1y ago

I tried doing something like this on an ESP32 last year, I wanted to understand how to do an actual mesh with devices that can't transmit and receive at the same time, but I didn't find documentation. I managed to get 2 devices communicating across town at least ! (After having antenna issues)

mytailorisrich 1y ago

Previously [2023]: https://news.ycombinator.com/item?id=35882967 https://news.ycombinator.com/item?id=35882967

embedding-shape 1y ago

Chat/text over LoRa always sounded intriguing! I'm merely a 1000km away from Sicily (which antirez say they wanna cover with the network at first), I wonder if it would be possible to do what AM radio does, bounce against the ionosphere and get huge ranges for transmission? Maybe it would need way too much transmission power? Maybe hopping all the way P2P style makes more sense, although surely would be slower.

bigfatkitten 1y ago
Not at 900MHz. Skywave propagation mode is only available under about 30MHz. Above that, the signal reliably continues on into space. At frequencies this high, you’re realistically limited to near line of sight paths.
- embedding-shape 1y ago
  > Not at 900MHz Shame, but at least now I understand why, thanks :) > you’re realistically limited to near line of sight paths Wonder exactly how far one would be able to get up to reach 1,000km line of sight, assuming you put both points equally far up. Guessing it's the curvature of the earth that gets in the way at that distance?
  - bigfatkitten 1y ago
    Yep. There are cubesats running LoRa payloads in low earth orbit[0], and between mountaintops, terrestrial paths of hundreds of km are possible[1]. [0] https://www.hackster.io/news/fossasat-1-an-open-source-satellite-for-the-internet-of-things-7f31cab00ef5 https://www.hackster.io/news/fossasat-1-an-open-source-satel... [1] https://meshtastic.org/docs/overview/range-tests/ https://meshtastic.org/docs/overview/range-tests/
    - embedding-shape 1y ago
      > Using metal tape measures to build simple quarter-wave monopole antennas is a hack to that’s actually pretty common in the small satellite community This is just too crazy, thanks a lot for sharing these links! :)

mdhb 1y ago

I think there’s some real value in WANs that are independent of both the internet and existing telco infrastructure but I don’t think I would put a specific transport at the centre of its design. I think you would be much better off with something like bundle protocol v7 and delay tolerant networking as the actual centrepiece and have something like LoRa as one of many transport link options. Maybe we are talking about a different threat model here but LoRa as the centrepiece falls apart really quickly the moment someone somewhere decides they don’t want your WAN to exist anymore.