Read Data ST25DV - nfc

Question

I made my own board with an STM32L031K6 and an ST25DV64K NFC chip. I am using the android App "NFC Tools". I can read the UID of the NFC chip with the app, so the antenna is correctly tuned. I can also read the UID with the microcontroleur via the I2C bus. When I write into the eeprom memory of the NFC chip with the microcontroleur, I can't read the data with the NFC app. It says that the tag is empty. I think I am missing a configuration, but I can't find which one.
Here is my code, executed once:
uint8_t ToWrite = 15;
uint8_t Password[17] = {0}; //Default password is"00000000"
Password[8] = 0x09; //Validation Code
// ST25DV_Address_E21 0x57 << 1; // Device select code= 0b1010111 ; E2 = 1
Password_Address = 0x900
HAL_I2C_Mem_Write(&hi2c1, ST25DV_Address_E21, Password_Address, 2, Password, 17, 0xFFF);
HAL_Delay(200);
//Read the UID
HAL_I2C_Mem_Read(&hi2c1, ST25DV_Address_E21, 0x18, 2, UID_Read, 8, 0xFFF); // This line works, UID displayed in the app and in the debugger are the same
HAL_Delay(500);
//Write some data in the eepprom memory (first address: 0x00)
for(int i = 0; i< 250; i++)
{
ToWrite++;
HAL_I2C_Mem_Write(&hi2c1,ST25DV_Address_E21, i, 2, &ToWrite, 1, 0xFF);
}

Answer 1

When you are writing the data in the EEPROM from address/block 0, you are simply overwriting the capability container values with all zeros. The correct way to do is initialize your tag, then write the data from block 4 and onwards.
The CC values look something like this:
0xE1, /* (block 0) */
0x40, /* (block 1) */
0x40, /* (block 2) */
0x05 /* (block 3) */
Followed by other key header values depending on the NDEF message type. Here I am illustrating for NDEF TEXT:
0x03, /*(block 4) NDEF message type (block 4) */
0x0D, /*(block 5) NDEF message length (blobk 5) eg, 13 byte message starting from here */
0xD1, /*(block 6) NDEF Record header: MB = 1, ME = 1, CF = 0, SR = 1, IL = 0, TNF = 001 > 0xD1 */
0x01, /*(block 7) Type length */
0x09, /*(block 8) Payload length = 9 (from language code) */
0x54, /*(block 9) Msg Type = Text */
0x02, /*(block 10) Language code size */
0x65, /*(block 11) Language = English, 'e', */
0x6E, /*(block 12) 'n', */
'A', /*(block 13+)Payload data */
'B',
'C',
'D',
'E',
'F'
A good reading resource to understand the NDEF payload format is here.
Hope this helps!