HT-M00 missing data

#1

I have an HT-M00 connected to TTN, but I’m also monitoring it via USB and the onboard LED.

And I have a number of things that can act as Lora nodes, but let’s take an official TTN Node as an example.

I have the HT-M00 and the TTN Node about 30cm apart on my desk. And when I press the button on the front of the node I see the blue LED on the node light, so it’s definitely working.

But the HT-M00 only sees maybe 20% of those button presses, confirmed by the green LED on the HT-M00 motherboard, the HT-M00 display, the USB output and also the TTN console.

What’s wrong? I don’t seem to have this issue with other gateways.

#2

hi,

Have you changed the Preamble length?

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图片.png810×705 146 KB

https://heltec-automation-docs.readthedocs.io/en/latest/gateway/ht-m00/qucik_start.html

#3

BTW, maybe I can’t understand your meaning well. Could you explain it more?

#4

Are you saying that you can only use 3rd party lora nodes with the HT-M00 if you change the preamble on each of them? What about devices where you don’t have access to the code? Things like commercial temperature and humidity nodes? Will they just not work properly with the HT-M00?

#5

The official TTN node has a button on the front. Pressing this button forces the node to send data. When I use it with a different node (e.g. the official TTN node) the data is always seen, but when I use it with the HT-M00 only maybe one in every 6 or seven button presses is received by the gateway. When it works the data is received correctly, but most of the transmissions from the node are missed.

#6

You need change the preamble length when you use the 3rd party lora node.

#7

As my talk, you have not change the preamble length. Packet loss is normal.

If you change to 16, There should be no packet loss.

#8

I see that I need to change the preamble length from 8 to 16, but exactly how do I do that? I see some code where it is referenced, but where is that code? Do I need to compile a complete new firmware for the device or this the a pre-built version that I can just flash – that would be much simpler!

Many thanks for your help.

#9

You don’t change the preamble on the gateway.You have to change it on every device that you want to connect TO the gateway. And that’s not always possible, which is why I sent my HT-M00 back to Amazon for a full refund.

#10
  • First of all, in the LoRaWAN protocol, users are allowed to modify the preamble. Those nodes that cannot modify the preamble are their problem.
  • Then, the node that has modified the preamble can still access other gateways normally without any impact.
  • The most important thing is: HT-M00 is positioned as a low-cost gateway. Our purpose is to allow users to use the various cloud servers and excellent LoRaWAN protocols with lower expenses. Price and performance, you can only choose one… I think everyone can understand this simple truth.

In other words, it’s like buying a car. If I have enough money, of course I would like to buy a V8 or even a W12 engine car, such a car will bring me a perfect experience in all aspects. But if the money is not sufficient, then I have to buy a cheap car with L4 or L3 engine. But the disadvantage is this car will not bring me good acceleration, performance, and experience.

Regarding the issue of HT-M00 dual-channel gateway, we have emphasized the issue of the preamble to all agents and asked them to add explanations in prominent places. You can dislike our HT-M00 gateway, but please don’t interfere with others’ judgment.

1 Like
#11

hi,

what is your lora node? cubecell or our esp32 lora nodes?

#12

Why does the HT-M00 dual-channel gateway need to modify the preamble length?

In some single-channel gateway projects on GitHub, CAD methods are generally used to detect the received data. This has the advantage of high efficiency, but the disadvantage is that errors often occur in the scanned spreading factor. For example, SF8 may be recognized as SF7 or SF9. This will cause serious packet loss. Some people may say that the packet loss of the single-channel gateway is fine, but have you tried more than 10 nodes and the distance is far away?

So we changed a way to detect data packets, which is what we call a digital baseband algorithm, this way can minimize the packet loss rate. Unfortunately, the preamble length of the node must be modified to ensure that there is enough time to determine the information of the data packet. Choose to modify the preamble length to ensure reliable communication? Or choose not to modify the preamble but will increase the packet loss rate? How would you choose?

Can I not choose? Of course… Just buy a standard gateway with SX1301/2/8 baseband chip, but its only disadvantage is that it is expensive.:joy:

#13

Ok, I understand. Thanks. So I can expect to receive packets on this little gateway on all SF7-SF12 so long as the frequency is one of the two selected on the setup and so long as the preamble is modified?

#14

The answer is YES:grinning:

#15

Ok, and this is exactly what is happening :slightly_smiling_face: