How do you decode "ADDR_DeviceID" of 32398 tag using 28440 reader/writer?

lb-hobby

Hi,

I've been Googling, trying to find an answer to the above question, with no luck. How do you interpret the 4 bytes of the "ADDR_DeviceID"? The 28440 manual says: "ADDR_DeviceID is a read-only value used to identify the specific tag family (for example, EM4150). The 32-bit value contains a family code, version code, reserved/unused bits, and a checksum value." Is the "Family code" in the first byte sent for a "ADDR_DeviceID" read command and "Version code" etc. in the following bytes?
I bought three 32398 tags from Parallax.com and each one has a different MSB returned for "ADDR_DeviceID". One is CB 00 10 32, other is 8E 00 10 32, and last one is 49 00 10 32. Why does the MSB of each tag's "ADDR_DeviceID" change when all 3 tags are the same?

I'm not sure if I will use this "ADDR_DeviceID "info in my projects but I sure am curious.

Thanks,
Larry

kwinn

Each tag will have some data that is the same within that tag family, some data that is specific to that tag, and a checksum value that will vary since the checksum is calculated from the other bits in the tag. This is pretty much standard for RFID tags and cards.

lb-hobby

Thanks for your input kwinn. But you haven't really answered my question. I know the names of the 4 bytes returned by the read "ADDR_DeviceID" query (family, version, reserved/unused bits, and a checksum value). I want to know how to decipher these bytes. Like, what value is the first byte returned for the "family code" for a 32398 "World Tag". It must be different than that of a 28142 "World Tag".

kwinn

That is information the tag manufacturer would have and might be somewhere on the internet. They might be willing to provide it if you asked. As far as RFID goes, with the exception of the 26 bit cards there do not seem to be any universal standards for bit lengths, parity, checksum, or data bit organization. It seems every manufacturer has their own proprietary standard.