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Help with writing NDEF message via i2c for M24SR

Question asked by yi.jonathan on Oct 6, 2014
Latest reply on Jan 13, 2015 by yi.jonathan

Hello,

I'm having trouble writing an NDEF message to the M24SR (with 8KB EEPROM) via i2c.

I am able to correctly write an NDEF Text Message via the official M24SR Android app.
I am able to correctly read the NDEF File via i2c.

However, when I try to write "hello world" via i2c to the NDEF file, the M24SR Android app reads an empty NDEF.
Here is the i2c sequence of what I've tried:

            (kill RF)
AC 52
            (select NFC)
AC 02 00 A4 00 0C 02 E1 03 D2 AF
            (5 reply bytes read)
02 90 00 F1 09
            (select CC)
AC 03 00 A4 00 0C 02 E1 03 D2 AF
            (5 reply bytes read)
03 90 00 2D 53
            (read CC length)
AC 02 00 B0 00 00 02 6B 7D
            (7 reply bytes read)
02 00 0F 90 00 44 45
            (read CC file)
AC 03 00 B0 00 00 0F A5 A2
            (20 read  bytes read)
03 00 0F 20 00 F6 00 F6 00 F6 04 06 00 01 20 00 00 00 90 00 A9 F3
            (select NDEF file)
AC 02 00 A4 00 0C 02 00 01 3E FD
            (5 reply bytes read)
02 90 00 F1 09
            (erase NDEF length)
AC 03 00 D6 00 00 02 00 00 6B 37
            (5 reply bytes read)
03 90 00 2D 53
            (update binary NDEF with "hello world")
AC 02 00 D6 00 02 0B 68 65 6C 6C 6F 20 77 6F 72 6C 64 2F FC
            (5 reply bytes read)
02 90 00 F1 09
            (update binary of NDEF with length of "hello world" = 11 = 0x0B)
AC 03 00 D6 00 00 02 00 0B
            (5 reply bytes read)
03 90 00 2D 53
            (deselect)
AC C2 E0 B4
            (3 reply bytes read)
C2 E0 B4

Again, after this sequence, when the NDEF is read via i2c, "hello world" is found, but the Android app sees an empty NDEF. I've tried appending the same "header" found when reading the Android-written NDEF via i2c, however the replies do not have a correct CRC.

Can anyone please help clarify the implementation and point me in the right direction?

Thanks in advance,
Jon

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