问题
The SDK provided along with NFC reader does not work and we are not able to write data / tag using the Tools available with SDK. The main issue is that the data written using another tool does not remain in the device for permanently. When tag is scanned using Android device, reader gets clear and we have to to write data again. I have checked and tried instructions from https://github.com/fkooman/nfcip-java/blob/master/nfcip-java/doc/ACR122_PN53x.txt but it does not work.
So, we need help to understand what command is needed to keep data(tag) in Reader even if it has been unplugged from the computer. The reader needs to be working in emulation mode and should provide tags.
回答1:
I know this is old but ranked in google so...
The ACR122U does not have any memory so it cannot save any state. You need to use it as you mentioned - writing to the device on each use.
Hope it helps someone.
回答2:
First of all, the ACR122U was mainly designed as a contactless smartcard reader and not as a card emulator. However, it is possible to do host-based card emulation (HCE) with this device (see How to card emulate with ACR122U-A9). But note that there are issues with some versions of the ACR122U (e.g., see The PN532 configured as target has been released by its initiator).
Nevertheless, all this is host-based card emulation. So the ACR122U only acts as the contactless front-end for emulating a tag (or contactless smartcard). It's the host (the computer) to which the ACR122U is connected to that performs the actual emulation.
Thus, the ACR122U is not a stand-alone device that you could program to act as a tag. You always need an application running on the computer that is connected to the ACR122U (via USB) to perform the actual emulation.
来源：https://stackoverflow.com/questions/17145264/nfc-reader-acr122u-a9-not-holding-tags