You know the NFC tag with NFC chip and antenna, the NFC chip able record data and manages the communication with the NFC reader.
Data for NFC tags is commonly measured in units called bytes and each byte is equivalent to approximately one character of text.
In an NFC tag, there will also be a memory that is used for the chip itself and for other functions. For example, each NFC tag has a unique ID (usually 14 characters long) which takes memory space. The UID cannot change.
When writing a standard NDEF information by NFC writer, such as a web link, to an NFC tag there will always be some extra bytes of hidden information which tells your phone what type of data you have stored. While this is typically only around 5 bytes, it means that your available memory reduces further.
For example, the NTAG210 NFC TAG chip with the total memory 64 bytes. and the programmable part is 48 bytes. To store a web address, you will also need to store 8 bytes of ‘hidden’ data which leaves you with 40 bytes for your actual URL.
If you are storing a web address, you can reference the below :
|NFC Chip||Usable Memory|
|MIFARE Ultralight||48 Bytes|
Each NFC chip’s memory is divided into two sections – user memory and system memory. For example, the NTAG210 has 80 bytes of memory, only 48 bytes of memory is actually available to be encoded.
From that 48 bytes of user memory, there are also some additional data that gets included with your data. So NFC readers can read what type of data you are storing, for example, a web address or text.
The web address is 8 bytes, the ‘http://’, ‘https://’, ‘http://www.’, or ‘https://www.’ are same amount of memory space.
The 8 bytes consists of two parts. The entire user data is called an NDEF message. The NDEF message can contain one or more NDEF records, such as a web link. In most encoding situations, there will be just the one NDEF record.
Three bytes are used to define the NDEF message, it’s length and the end of the whole message. The other five bytes define the NDEF record including it’s type (such as a URI), the URI identifier (such as ‘http://’) and the length of the type and payload (your data).
If your data is too long , you can choose the NTAG 213 NFC TAG, it will handle most longer URL’s but on larger deployments is often good to use the cheaper NTAG210 NFC tag.
To keep things simple, a byte is composed of eight ‘bits’. A bit is a single binary ‘switch’ – 1 or 0 (think yes or no). So, a byte contains eight 1’s or 0’s, for example 10110101. However, each bit in the byte has an increasing value, like the number 123 can be broken into one hundred, two tens and three. So, ’10’ is actually ‘worth’ 2, and ‘100’ is worth 4. Ultimately, this means that the full ‘11111111’ is worth 255 providing a total combination of 256 numbers (0 inclusive).
In the case of NFC tags, this range of numbers relates to a standardised set of letters and characters. So, the number 114 relates to the letter ‘r’, 115 to the letter ‘s’ and so on.
So now you know how much memory you might need, working out which chip you need is simply a case of selecting one with enough usable memory for your data. In general, our preferred options are the NTAG210 NFC tag or the NTAG213 NFC tag. DO RFID tag manufacturer produced various NFC tags with Good performance and good price.
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