Is it intended that for devices that do not have a preconfigured hardware based DevEUI (as RFM9x), an segment is provided, which does not collide with the others?
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You could always add a chip that gives a unique DevEUI so that you’ll know you won’t clash with any other device.
Andrew
Some microcontrolers have a unique ID embedded. I’m thinking of STM32 for example, which will same a bit of BOM.
thanks for the suggestions so far, but adding some chips makes existing hardware much more complicated.
e.g. MoteinoMega with RFM95W has no space for it.
Teensy3.2 and all other projects based on ESPxx are mostly built from standard components.
so I think I go further by using an 8 byte random number … and assuming that in combination with the AppEUI no collisions should occur.
The MoteinoMega can have a SPI flash - bnot shure this is the version you have. These have a 64 bits unique IDs. Maybe, you can rely on them.
The whole point of an EUI (Extended Unique Identifier) is that they are guaranteed to be unique. If you start using random numbers for the EUI, it’s not going to be an EUI anymore.
I’m not sure if this is true, but I suppose that you could also base your EUI on a MAC address you already own, for example the MAC address of your WiFi card (which the manufacturer sold to you). These MAC addresses are 48 bits long, which means that you can fill the first 48 bits of the DevEUI with your MAC address, and choose the remaining 16 bits yourself.
If you buy chips with unique id there is no need to mount the chip on the module, just read the unique id, assign it to the device and make sure you do not reuse the id for another device. Buying the chip ensures you bought the right to use the unique id embedded in it. Or if you want to use a large block of ids, buy the block like TTN did 
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There is a standardized way to translate a MAC address to a EUI-64, though I can’t recall where it is documented. IIRC it is a 1-to-1 mapping that is more complex than just padding the end with zeroes. Your suggested scheme of adding 16 bits to fill up the MAC address would actually mean that every single MAC address would prevent 2^16 addresses from being used.
Using this standardized way is only possible if the manufacturer actually supports this scheme, meaning he guarantees that he will not use the DevEUI that results from translating a MAC address for any other purposes, so you can use it here. If the manufacturer just uses his OUI to generate both MAC addresses and EUI-64’s independently, uniqueness is not guaranteed.
Having said that, I believe the spec requires using a (by definition unique and assigned by the IEEE) EUI-64 identifier for the DevEUI, but in practice it might be sufficient to use any identifier that is unique within the AppEUI. Any overlap in DevEUI can be handled, as long as the AppEUI is different. IIRC this is true for at least TTN, other LoRaWAN networks might be more strict / more easily confused.
oh yes, I know what a MACaddress is and how to convert it, but except the nodes with ESPxx don’t have them.
It’s not a problem of mine, it’s a general problem of us all, having non-hardwase-numbered devices
THANKS!
For development this should be okay.
but can you buy just a few of these chips ?
maybe in the future in the TTN webshop… a special 'hard to get for hobbyist chip page with special discounts ’ 
Or start selling EUIs in the webshop
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unavoidable, there is no free in free beer in the future imho
** from the perspective of the hardware designer, its off course very important to know now, if your integrated micro chip 24AA02E64 in your node design, are worthless in the (near) future*
Aren’t there any cheap RFID / NFC tags with EUIs pre-burned onto them? If so, it would serve dual purpose, not only gives you an id, but also makes it easy to get the id of a sensor by just moving your phone close to it.
The trick with free beer is usually that someone else pays for it.
For AppEUIs we solved this by buying a block of EUIs. Maybe we could crowdfund another block for DevEUIs, but it’s probably easier to just buy some cheap (less €0.30) chips that have an EUI. Just search for “EUI” on farnell.com
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exactly, but you cannot buy just 10 chips… thats why I suggested the TTN webshop to the rescue, maybe in cooperation with Micro Chip / Semtech , maybe a combined purchase effort…or what you suggest a crowdfund.
You can even buy singles at Farnell if you are a business customer, so 10 is not problem at all. For Dutch private customers I know of at least one electronics parts retailer willing to order and resell parts from Farnell, however the overhead cost for each order would make the chips relatively expensive.
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I like the idea of crowdfunding a block of DevEUI’s. How about if TTN buys these and offers them on the TTN webshop? I’ll buy 10 at least (for starters). 
same here.