Thank you for your reply.
If I understand correctly, for my use case (hobby projects) it is not obligated to receive (and process) the MAC commands. I should of course be careful about the messages I send (spreading factor, transmission power, duty cycle) and should respect the 868 MHz band rules and the TTN Fair Access Policy. In my use case (SF7, low transmission power and duty cycle below 0.001 %) I think I’m in the clear. Or should I still be worried?
A good remark is that the device will not have LoRaWAN certification, but if I understand correctly, certification is not mandatory for TTN? If so, this should not be stated as a problem but can certainly be noted as a remark when it is reasonable that the project will be used commercially.
Regarding the receiving part, reading posts from this forum I conclude it is possible to receive and process the MAC commands with an attiny8x + rfm95w combination (link). You said before that this combination of hardware will never be compliant. I assume that you probably meant never be certified instead of compliant (because you say compliant specification does not explicitly state receiving/processing MAC commands to be mandatory). But when receiving and processing of MAC commands are implemented, why should it still fail certification? Can you shine some light on that?
It is confusing to read such a resistance against a project like this. I can understand that it is maybe not the approach other people would prefer, but that doesn’t mean it is wrong and cannot be tweaked to something that is right without using other hardware. I think it is good the keep an open mind about different use cases and levels of skills. Not everyone is building a commercially device in high volumes, a lot of people are trying to learn something here.
I actually started tinkering with Raspberry Pi’s (not with LoRa at the time), but after some time I thought, that’s quite some overhead, running a full OS, to control some simple electronics. That was the start to first learn about some Arduino stuff and later a dive into bare attiny chips. Which are, funny enough, for a lot of small projects still overkill. And now I am used to the Atmel chips and those are lying around here and I also use them for other projects.
You say this node is not efficient, “efficient” can be interpreted in several ways. I think the combination is quite efficient regarding power, size and costs, but maybe not the most efficient looking at the full development process. But yeah, buying an off-the-shelf node would then be the most efficient, but where is the fun in that? But still, if you know a module with better specs (size, power consumption) without being more expensive, I would love to know.
Receiving LoRaWAN messages was already something on my learning list, not necessarily for processing MAC commands but primarily for other things. I will certainly dive into the specifics of that in the future. Looking at this conversation and multiple other posts at this forum, I think an open conversation about the development of this kind of nodes is a positive thing.