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dernasherbrezon / sx127x

Library to work with Semtech chips SX1276/SX1277/SX1278/SX1279.
Apache License 2.0
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Wrong version number #15

Closed ahsimb closed 1 month ago

ahsimb commented 2 months ago

I've got an SX1272 module, which I thought would be supported by this library. However, the version (or Semtech ID) I am getting at the address 0x42 is 34 as per the product datasheet. The library expects the value 18 and refuses to work after seeing a different number.

Is this a new, incompatible version?

dernasherbrezon commented 2 months ago

Yes, look like incompatible. I will have a look into the differences to sx1276/77/78/79.

ahsimb commented 2 months ago

Thanks a lot.

dernasherbrezon commented 2 months ago

Where did you get this chip? I can't find any dev board to buy and test.

ahsimb commented 1 month ago

Here is what I bought.

ahsimb commented 1 month ago

They claim their module can transmit over up to 16 km in theory and up to 12 km according to their tests. What makes it cover a longer distance compared to other modules with a similar chip I do not understand. I wanted to give it a try. Disclaimer: I am not particularly knowledgeable in this area. The project is more like a hobby for me.

dernasherbrezon commented 1 month ago

£12.00 is a bit expensive. I found this one https://www.ebay.co.uk/itm/193877948103 for $4.78. According to Semtech SX1272/73 can achieve a sensitivity of over -137dBm while sx1276 can achieve a sensitivity of over -148dBm. I.e. slightly better.

ahsimb commented 1 month ago

That's what the supplier who I bought my module from says in the technical manual:

"The most important aspect of any RF Module is to maximise the performance of the transceiver at the external module pads. In particular the impedance matching network which is the most sensitive section of the RF module design. In order to maximise signal propagation to the external pad of the module, a specific layout is required which is not (usually) the smallest physical size (beware of small RF modules!). Many RF Module manufacturers simply reproduce the IC manufacturers data characteristics where in practice the Module RF performance is considerably lower."

Does it make sense?

dernasherbrezon commented 1 month ago

No :)

Semtech is the manufacturer of these chips. If they believe sensitivity is better on sx1276 series, then this is most likely it. They know internals of the chip better than anyone else. Think of it as a theoretical sensitivity. In practice, these chips need to be soldered and integrated somewhere. And this is where numbers can be different. Maybe RFSolutions did a good job designing and testing the board. And it might be better than someone' else result with sx1276. But it is also possible that someone' else did a good job integrating sx1276.

But all of this is irrelevant if the final board connected to unbalanced antenna or working in a very noisy environment.

ahsimb commented 1 month ago

They probably did a good job if the results of their tests were to be trusted - 12+ km with a line of sight and 3 km with no line of sight. This is considerably better than what I have seen elsewhere (again, I am not a specialist). I don't know why they use sx1272 instead of the more advanced sx1276. Probably because they have a big stock of sx1272 which they want to get rid of.

dernasherbrezon commented 1 month ago

Yes, most likely. sx1272 is hard to find.

FYI Stock LoRa chips can receive data from satellites which is slightly more than 12+ km. https://tinygs.com/satellite/Norbi

ahsimb commented 1 month ago

Very interesting. Thanks for sharing. I guess it's not exactly my case, as the transmitter on a satellite takes a bit more power than what AA batteries can give.

dernasherbrezon commented 1 month ago

I compared registers between sx1272/73 and sx1276/77/78/79 and found lots of differences. So this project is not suitable for sx1272/73 chips. I probably create a separate project to support that. In the meantime, better use some other projects.