One more "Which implant should I get and other dumb questions"

XEMON · September 10, 2021, 11:26pm

This thread helped understand a bit better the Apex/NDEF: NDEF size of the Vivokey Apex line

the size of the NDEF container is what matters… so on the DESFire EV2 chip, which has 8k, you can define an NDEF container that is 1k, 2k, 3.878317k, 5.89k or all 8k… if you do that, then you can write up to 8k of NDEF data into the container that is formatted into one or more NDEF messages, each of which can have one or more NDEF records. Typically there is only ever one NDEF message, and inside that there are one or more records… so in NFC Tools when you want to write multiple things to your tag, you are creating multiple records within the single NDEF message on the chip… it just happens that on the DESFire that NDEF data is stored inside of an application ID that is defined as a generic binary data storage “file” (applications are called files on DESFire chips) with a specific AID of D2760000850100… on the Apex, the AID D2760000850100 will be a special javacard applet that also supports generic memory read/write commands for storing NDEF formatted data… and the size of that container on the Apex can, in theory, be up to 300k or more… but because of the limitations of data storage and throughput practicalities, we have limited the maximum size of the NDEF container to 16k for the NDEF applet on Apex. We did have a 32k size at one time, but it caused actual problems because it took so very long to provision NDEF data storage within the applet that phones and readers were basically timing out the NFC command and giving up.

Thanks