EM4100 RFID issue: Emulation does not work

[swittenberger]

Describe the bug.

Hello, I've had 3 different EM4100 tags that I could copy without any issues, but when emulating the tag, the reader doesn't detect anything.

I've been told on discord that a reboot might help, but it didn't. What other info can I give?

Reproduction

1. Read EM4100 tag
2. Emulate EM4100 tag
3. Try to open the door with flipper
4. Notice it doesn't work.

Target

No response

Logs

No response

Anything else?

No response

[dontbug]

I have the same problem of not being able to register on the electra chips, but i could on the T5577 chips that i ordered from aliexpress. There were times when i couldn't write from the ordered ones, but it's quite possible that they are not the T5577 model specified by the seller, and i made a refund.

[itrack]

@dontbug In my case, I can write anything else on T5577 tags. I write other access keys, it went without any problems. When I try to write Electra on T5577 it does not work. I tried 4 different types of T5577 tags, same result.

[skotopes]

@itrack have you tried to read 5577 after write fail?

[itrack]

@skotopes Yes, the tag does not change

[skotopes]

@skotopes Yes, the tag does not change

interesting, could mean that formed payload is incorrect and can not be written to the card. Can you share key?

[itrack]

Sure: electra.zip

[itrack]

btw. emulating this tag works

[skotopes]

Sure: electra.zip

All works:

• Parsing payload
• Emulation
• Writing to 5577
• Reading 5577

[itrack]

Interesting that writing works for you, how could this be debugged? I can't explain, I would have thought it was a problem with the RFID module if I couldn't write other cards, but it works, just in this specific case it doesn't.

Are there several hardware versions?

[skotopes]

Interesting that writing works for you, how could this be debugged? I can't explain, I would have thought it was a problem with the RFID module if I couldn't write other cards, but it works, just in this specific case it doesn't.

Are there several hardware versions?

Not in terms of RFID. Also if you can write other types you should be able to write this one too.

[itrack]

I made another video testing several cases:

• Trying to write an electra tag (failed)
• Trying to write another tag (successful) On tags where an electra tag failed, another tag succeeded.

What could be the explanation?

https://www.youtube.com/watch?v=mKwfsRf2ZaI

[skotopes]

@itrack we don't provide support for 3rd party firmware. If you use it then address all issues to appropriate firmware developers.

[itrack]

here is a video with the official firmware, it is the same result: https://www.youtube.com/watch?v=AbJDa9PVRl4

[itrack]

I put back the original firmware, I did another test and discovered something a little strange. On one type of tag although it gives error it writes part of the original tag. Nothing has been written on the other two tags types.

Original tag:

Clone tag: