[Internet of vehicles prototype system II] database + application layer protocol design

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IOT prototype system navigation

【 Prototype system of Internet of vehicles ｜ One 】 Project introduction + Demand analysis + Outline design https://blog.csdn.net/weixin_46291251/article/details/125807297

【 Prototype system of Internet of vehicles ｜ Two 】 database + Application layer protocol design https://blog.csdn.net/weixin_46291251/article/details/125808107

【 Prototype system of Internet of vehicles ｜ 3、 ... and 】 Raspberry pie design + Simulate the base station program https://blog.csdn.net/weixin_46291251/article/details/125808229

【 Prototype system of Internet of vehicles ｜ Four 】adhoc networking +frp Intranet through https://blog.csdn.net/weixin_46291251/article/details/125808621

【 Prototype system of Internet of vehicles ｜ 5、 ... and 】 Fore and aft end separation https://blog.csdn.net/weixin_46291251/article/details/125808674

【 Prototype system of Internet of vehicles ｜ 6、 ... and 】 Effect display https://blog.csdn.net/weixin_46291251/article/details/125808845

【 Source download 】https://download.csdn.net/download/weixin_46291251/86227197

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【 Prototype system of Internet of vehicles ｜ Two 】 database + Application layer protocol design

Application layer protocol design

The communication between the back end and the car raspberry pie is through socket On going , Therefore, we need to define a private agreement , Distinguish different types of data messages . Data message adoption json Format for transmission .

Overall speaking , Messages can be divided into two categories , One is control message , One is data message . The control message is used for the user to control the car , Data message is used to transmit data information .

Field overall design

The specific fields and corresponding descriptions are shown in the following table ：

Data field	Content description
pac_type	Packet type
control_type	Distinguish between different message function types
src_id	The sender id
dst_id	The receiving party id
piece	Message fragment mark
time	Sender timestamp
ack	identification ack
length	The length of the message
state	Status code
alternate	Keep field

Specific fields

pac_type

The first is the data message type field , This field mainly identifies the flow direction of the message , There are three main directions ：

• Raspberry pie To The base station
• The base station To Raspberry pie
• Raspberry pie To Raspberry pie （ Corresponding forwarding to the situation ）

Packet type (pac_type)	Data flow	code
	pi -> pc	01
	pc -> pi	10
	pi -> pi	11
	Retention type	00

control_type

The control type field is used to identify the specific corresponding function of the message , This part should be based on pac_type To make a comprehensive judgment , Different pac_type Will correspond to different meanings ：

• For raspberries sent to the base station to the type , It is raspberry that sends feedback data to the base station to the message , It is divided into trajectory data 、 Sensor data 、 And raspberry pie have three kinds of low power .
• For the message type from base station to raspberry , It is mainly the control command issued by the base station , There is a beginning / Stop moving 、 open / Turn off the sensor 、 One click return and forwarding （ Forward the command to the car that is not within the range of the base station ）.
• For raspberry pie to raspberry pie type , Similar to the second , Without the forwarding function .

Field	Instruction meaning	code
control_type	pac_type == pi -> pc	Trajectory data	000
		Sensor data	001
		Low power	010
		Unable to avoid obstacles	011
		Reserved instructions	100
		Reserved instructions	101
		Reserved instructions	110
		Reserved instructions	111
	pac_type == pc -> pi	motion	000
		stop it	001
		Turn back	010
		Turn on the sensor	011
		Turn off the sensor	100
		forward	101
		Reserved instructions	110
		Reserved instructions	111
	pac_type == pi -> pi	motion	000
		stop it	001
		Turn back	010
		Turn on the sensor	011
		Turn off the sensor	100
		Reserved instructions	101
		Reserved instructions	110
		Reserved instructions	111

state Field

state Fields are mainly used to feed back the data of instruction execution , Success 、 Failure 、 Timeout etc. , Some code is also reserved to pass custom state .

Status code (state)	meaning	code
	success	000
	Failure （ Overtime ）	001
	Failure （ The instruction is illegal ）	010
	Failure （ reason 3）	011
	Failure （ reason 4）	100
	Reserved state	101
	Reserved state	110
	Reserved state	111

Other fields

ack Field ：

After the system receives a message , You can reply to a ack message , Indicates that you have received the message （ It can be combined with digital signature to realize two-way undeniability ）

- Receive one message at a time , After receiving according to the above logic , Just send one ack Send the message to the sender , Indicates that the message has been received .

- One message at a time , After sending according to the above logic , Just charge one ack message , Verifying this message means the end of this transmission .

piece Field ：

This field is mainly used to process large messages Fragmentation problem .

Adopt the method of slicing , Head pieces Field to specify whether the current message is the last fragment , Send a completed header and partial message each time ( Depending on MTU).

The receiver receives one at a time MTU The size of the message , Analyze the head pieces Field , Judge the ending condition , After receiving, combine all the data fields to get the completed big message

Data structure design

This part is mainly about the structure of the content field of the message transmitted between the car and the base station

Instructions

Field	meaning	give an example
direction（list）	The state of the four buttons	[False,False,False,False]
speed	Speed	50
diff_speed	Steering differential	20

data

Field	meaning	give an example
sensor_list	Sensor list
data_list	Data list
trace_stack	Path stack

Database design

conceptual model

Table structure design

The following table is designed ：

• user surface ： Store the user's account 、 password 、 The user types （ Grade ）、 Landing time
• sensor_info surface ： Store the type number of the sensor 、 name 、 grouping 、 Description information
• pi surface ： All raspberry pie numbers in the storage system 、 Authority level 、 Describe information, etc
• sensors surface ： List of all sensors in the storage system , Include the number of the sensor 、 Number of raspberry pie 、 Sensor type 、SN code （ If there is ）、 Authority level
• data_instruction surface ： The system issues / All instructions executed , Include instructions id、 user id、 Raspberry pie id、 Time 、 Execution status 、 Instruction type 、 Specific data of the instruction
• data_sensor: surface ： Sensor data sheet of raspberry pie feedback , Including data id、 sensor id、 user id、 Time 、 Specific sensor data
• data_trace surface ： Raspberry pie feedback track data sheet , Including data id、 user id、 Raspberry pie id、 Time 、 Specific trajectory data .

There are the following fields

• data_instruction : [‘id’, ‘user_id’, ‘pi_id’, ‘time’, ‘state’, ‘type’, ‘data’]

• data_sensor : [‘id’, ‘sensor_id’, ‘user_id’, ‘data’, ‘time’]

• data_trace : [‘id’, ‘user_id’, ‘pi_id’, ‘time’, ‘data’]

• pi : [‘id’, ‘level’, ‘description’]

• sensor_info : [‘id’, ‘name’, ‘group’, ‘description’]

• sensors : [‘id’, ‘pi_id’, ‘sensor_type’, ‘SN’, ‘level’]

• user : [‘id’, ‘passwd’, ‘level’, ‘reg_time’]

ER chart

Sensor table section

Instruction storage section

Path storage section

Sensor data section

total

The physical model ：

A little , see sql In the file

Crow‘foot chart