The Differences Between TTLV Data and JSON Data

Note: This chapter describes the differences between TTLV data and JSON data when the device-side selects the data format.

TTLV

TTLV, (i.e. Tag, Type, Length, Value), is a kind of hexadecimal data processed according to the protocol. TTLV format compresses the data into a smaller volume, which has a high utilization of space and does not allow the generation of redundant fields.

TTLV Features

• Compact data: With compact data and concise format, the data volume is small and the transmission between modules and MCUs is more efficient.
• High security: Data cannot be read without the document stipulated in the protocol.
• Not intuitive data: Data is not intuitive. TTLV format data can only be read after the document is parsed according to the protocol.

TTLV Format

Field	Length	Description
ID	13 Bit	Range 1–8191. Unique within different commands (cmd) (such as TSL model, device status, module information, etc.)
Type	3 Bit	Currently defined types (binary): Boolean false: 000 Boolean true: 001 Enumerations and values: 010 Binary data: 011 Structure: 100
Length	Different types have different length bits.	Different types have different length bits. See the table below for details.
Value		See the table below for details.

Detailed Parsing of Data Length and Data Value

Type	Length	Value
Boolean false	Null	Null
Boolean true	Null	Null
Enumerations and Values	1 Byte (identifier bit, 0 means positive, 1 means negative) 3 Bit (Attenuation 10 to the N-th power) 4 Bit (Number of data Bit, Bit of data field-1)	Content
Binary data	2 Byte (Number of data Bit)	Content
Structure	2 Byte (Number of members)	Content (If it is an array type, there is no feature ID and 0 is used for identification.)

Example:

Feature ID	Type	Value	Binary data	Hexadecimal data
1	BOOL	false	0000 0000 0000 1000	0x00 0x08
2	BOOL	true	0000 0000 0001 0001	0x00 0x11
3	Value	4	0000 0000 0001 1010 0000 0000 0000 0100	0x00 0x1A 0x00 0x04
4	Value	5	0000 0000 0010 0010 0000 0000 0000 0101	0x00 0x22 0x00 0x05
5	Value	258	0000 0000 0010 1010 0000 0001 0000 0001 0000 0010	0x00 0x2A 0x01 0x01 0x02
6	Value	0.18	0000 0000 0011 0010 0001 0000 0001 0010	0x00 0x32 0x10 0x12
7	Value	-0.32	0000 0000 0011 1010 1001 0000 0010 0000	0x00 0x3A 0x90 0x20
8	Binary data	0xAB	0000 0000 0100 0011 0000 0000 0000 0010 0100 0001 0100 0010	0x00 0x43 0x00 0x02 0x41 0x42
9	Structure	Parameter ,Type： Bool ：false ID：2 ,Type： Value ：10	0000 0000 0100 1100 0000 0000 0000 0001 0000 0000 0000 1000	0x00 0x4C 0x00 0x01 0x00 0x08

Image parsing：

JSON

Based on JavaScript (Standard ECMA-262 3rd Edition - December 1999), JSON is a subset and an open and lightweight data exchange format that uses text formats independent of programming languages to store and represent data. JSON object is an unordered collection of "name/value" key value pairs: start with "{" and end with "}". JSON components are as follows:

{
    "key":vlaue
}

JSON Features

• Self-description: JSON data is intuitive and easy for developers to read and write.
• Simple format: JSON data is relatively simple and can be easily packaged and parsed in MCU programming.

Example:

Feature ID	Type	Value	JSON Data
1	BOOL	false	{"1":false}
2	BOOL	true	{"2":true}
3	INT	100	{"3":100}
4	DOUBLE	12.3	{"4":12.3}
5	FLOAT	25.6	{"5":25.6}
6	ENUM	1	{"6":1}
7	TEXT	ABC123	{"7":"ABC123"}
8	DATE	1659664758817	{"8":1659664758817}
9	STRUCT	{"10":true,"11":100}	{"9":{"10":true,"11":100}}
12	ARRAY	[10,20,30]	{"12":[10,20,30]}

How to Select a Data Format?

• Without the need to migrate specified library files to generate and analyze data, JSON data is easy to be combine and read, but the number of data bytes it sends is more than that of TTLV. So it is suggested to use JSON format when sending less TSL model data.
• With compact data, TTLV format is more concise than JSON, but it needs to migrate TTLV library to MCU. So it is suggested to use TTLV format when MCU resources are sufficient and you need to send a large amount of TSL model data.