Is it possible to have multiple multicast groups for the STM32WLE5?

ALand.2 · ‎2022-05-16

Hi,

Currently looking into having multiple multicast groups on an STM32WLE5, using the LoRaWAN middleware included with STM32Cube_FW_WL_V1.2.0 package. When looking at "LoRaMacTypes.h" (in Middlewares/Third_Party/LoRaWAN/Mac), I came across the constant "LORAMAC_MAX_MC_CTX" which should control this, and it is currently set to "1". Right next to it, there's a comment saying: "ST_WORKAROUND: reduced LORAMAC_MAX_MC_CTX", and therefore I wonder: is it possible to increase this value, or has it been set to 1 deliberately due to some kind of issue with the STM32WLE5 chip?

I tried looking at the git logs of the STM32WLE repository (can't add the link to the repository due to being a new member) but since it seems like only complete releases are uploaded there, there were no commit logs which could point me to why that comment is there in the first place.

Louis AUDOLY · ‎2022-05-17

Hello @ALand.2,

Welcome to the community and thank you for your question!

In fact the number of multicast groups is fix to 1 due to different things.

First, in the specification from the Lora Alliance, it's written in the Remote Multicast Setup package that "An end-device implementing this package SHALL support at least one multicast group and MAY support up to a maximum of 4 simultaneous multicast contexts" (chapter 4.3 McGroupSetupReq). So you could at the maximum register 4 multicast groups.

This feature has never been tested because there is an idea of priority that has not been describe. Because you could use your multicast groups in the same time, but if they don't have the same configuration (frequency, data rate, etc...) the device cannot configure and listen to different Rx config in the same time. So this is a limitation of multicast groups, so as this feature is not clear and define properly, to avoid any issue, the number of multicast groups have been fix to 1. This is the only configuration that has been tested.

I hope this answer your question.

Best regards

ALand.2 · ‎2022-05-18

Hi Louis,

Thanks for the quick follow-up!

Well, that explains why that comment is there then. Anyway, I'll try to do some experimentation with this then (such as setting a static data rate, however, that won't solve the problem with different frequencies); at least I now know why it is configured the way it is then. :)

Regards,

Aron

Louis AUDOLY · ‎2022-05-18

Hi @ALand.2 ,

Ok let me know if you acheive to have multiple multicast group.

On the server side (if you do not use your own server), you may encounter issues because servers don't always give you the opportunity to register several multicast groups !

Regards

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