I want to send downlink messages from TTS to STM32WL end-nodes (class C enabled) by using multicast. However, I am not sure I have understood all the multicast process, especially on the server side (I work with TTS).
If I have already created an end-node device on my application and it already joined (with the OTAA) and sent uplink to my application, is it possible to add my end-node to a multicast group? If so, I am wondering about the device address. Indeed, when you want to create a multicast group with TTS, it works like an ABP profile. Device address, AppSKey and NwkSKey are asked. But which address and keys should I choose here?
Eager to learn, I am a beginner with multicast protocol! So, any advice is welcome!
I have seen your videos on Youtube - they are great!
Also trying to build Multicast environment with TTN.
But have some strange issue: multicast packet are queued but never rich a gateway interface.
Looks like they silently dropped by Network server.
Can you help me or show a right way?
In that situation, I assume the NS doesn’t know the path to use (it doesn’t know the gateway that must emit the downlink frame).
A solution is to specify that path with a JSON payload sent through a MQTT server or a HTTP webhook. The TTN documentation gives that JSON object (see Multicast | The Things Stack for LoRaWAN). However, I faced issues while using that JSON example (wrong place of comma, etc.). I recommend using that JSON example, adapting it to your application and checking the JSON syntax with a JSON tester (a dozen of them are online for free, e.g.: https://jsonlint.com/).
After that, there is another point to be aware of: the radio settings (frequency and data rate). They must be the same, both in the end-device and on the server for your multicast session.
Hi @olegt. I’m happy that you were able to config the downlink path. Before your message, I was skeptical that it was possible. Could you share your JSON config, please? Even though I managed to send the downlink path JSON (with corrections) through curl as the documentation suggests, I keep receiving the “no downlink path available” error. Did you use the MQTT/Webhook or the console (web) to send the JSON? Any detailed info regarding the procedure will be highly appreciated. Best regards!