My goal was to use one card/keyfob to access two different physical locations.
Before testing generic NFC tags, I also tested the official Aqara NFC cards. In my case, the official Aqara NFC card could not be used on two U200 locks at the same time. When I enrolled it on the second lock, the first lock no longer accepted it.
With the initialized generic NFC tag, the behavior was different: the same physical tag could be enrolled and used on both U200 locks at the same time.
I tested generic Mifare Classic 1K / 13.56 MHz NFC keyfobs.
Other compatible NFC tags may also work, but I only tested this specific type.
When the generic NFC tags were completely blank/unformatted, the Aqara U200 did not react at all.
At first, this made it look like the generic tags were not supported.
The solution
The NFC tag first needs to be written/initialized once.
I did this through Home Assistant NFC tag setup. Home Assistant wrote/created an NFC/NDEF tag ID/hash on the tag.
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Use a compatible generic NFC tag.
I tested Mifare Classic 1K / 13.56 MHz. -
Write/initialize the tag once.
I used Home Assistant NFC tag setup, but an NFC writer app may also work. -
Enroll the initialized tag in the first Aqara U200 lock.
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Test that it unlocks the first lock.
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Enroll the same physical NFC tag in the second Aqara U200 lock.
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Test both locks.
The same initialized generic NFC tag works on two different Aqara U200 locks at the same time.
In my case, the tag was not bound exclusively to one lock.
This is different from the official Aqara NFC card behavior I tested, where the card stopped working on the first lock after being enrolled on the second lock.
Do not rewrite or change the NFC tag after enrolling it in the locks.
If the U200 stores or checks the written NFC/NDEF data, changing the tag content may stop it from working.
Generic NFC tags can work with the Aqara U200, and the same generic tag can be used on more than one U200 lock.
The important part is that blank/unformatted tags may need to be initialized/written once before the U200 can detect them.
This may explain why some users report that generic NFC tags do not work. In my case, the blank tags were completely ignored, but after initialization they worked normally.
