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sandeepmistry / arduino-LoRa

An Arduino library for sending and receiving data using LoRa radios.
MIT License
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Channel selection (or: specific frequency) #194

Closed MITEL-UNIUD closed 3 years ago

MITEL-UNIUD commented 5 years ago

Hi, I am trying to make the LoRa Receiver example to function, using as a test sender a node made for TTN LoRaWAN with ABP (I do not care about content, just testing). Pin setup seems ok. From the API description, it seems that I have to select the frequency with LoRa.setFrequency(frequency), where frequency, from API documentation, is among 433E6, 866E6, 915E6. I have two questions regarding this: is 866E6 a mistake for 868E6, and then, if I want to listen on a specific frequency, may I set it directly (e.g., with 868100000)? Then I set spreading factor. I have set Sync word to 0x34 according to Semtech documentation.
Default coding rate (4/5) and default bandwidth (125) are ok. What else do I need to set? I still do not see received messages. Thanks (for the library and for the answer).

MITEL-UNIUD commented 5 years ago

Self-answers:

ricaun commented 5 years ago

Hello,

This library is not intended to use with LoRaWAN, but is possible to sniff some payloads... First, you need to check the frequency plan (https://www.thethingsnetwork.org/docs/lorawan/frequency-plans.html). I guess your plan is EU863-870. Default we have set Sync word to 0x34, coding rate 4/5;

Let's try channel 1!

Uplink Channel 1: 868.1 - SF7BW125 to SF12BW125 Set the frequency to 868100000 and SF7BW125 (Some codes randomize between the SF7BW125 to SF12BW125).

RX1 Downlink Channel 1: Same as the uplink In this case, is the same frequency, spreading factor, and bandwidth. And you need to Invert IQ Signals (Check the enableInvertIQ function). Usually, the gateway sends the downlink after 1 second from the uplink when is ABP.

RX2 Downlink Channel 1: 869.525 - SF9BW125 (RX2 downlink only) The Invert IQ Signals still enable, set the frequency to 869.525 and SF9BW125. The gateway sends the downlink RX2 after 2 seconds from the uplink.

That's it, this is the logic for Uplink and Downlink. But remember the LoRaWAN payload have a lot of encryption craziness and others tricks...

Stay tuned!

MITEL-UNIUD commented 5 years ago

Thanks, as you see from the previous message I was finally able to receive messages from a TTN node (actually, I was already receiving but not seeing them in the serial monitor). However, thanks for the InvertIQ explanation, I did not yet consider it. I know this library is not intended for LoRaWAN, and having already LMIC, in principle there is no strong need for others (althiugh LMIC is not Class C capable...).