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Quanzhi technology T3 development board (4-core arm cortex-a7) - mqtt communication protocol case

2022-06-11 18:27:00 【Tronlong】

This article mainly introduces based on T3 The processor MQTT Communication protocol development case , The explanation mainly includes MQTT Introduction to communication protocol 、 summary 、 Application scenarios and Mosquitto Tool installation 、mqtt_client Cases and mqtt_sinewave_pub Case etc. .

This guidance document is applicable to the development environment ：

Windows development environment ：Windows 7 64bit、Windows 10 64bit

virtual machine ：VMware15.1.0

Linux development environment ：Ubuntu18.04.4 64bit

U-Boot：U-Boot-2014.07

Kernel：Linux-3.10.65

LinuxSDK：LinuxSDK_AA_BB_CC_DD（ be based on T3_LinuxSDK_V1.3_20190122）

The test board is based on Chuang long technology TLT3-EVM It is based on Quanzhi technology T3 Processor design 4 nucleus ARM Cortex-A7 Domestic evaluation board with high performance and low power consumption , The dominant frequency of each core is up to 1.2GHz.

Evaluation board interface resources are rich , Lead out the double road network port 、 dual CAN、 dual USB、 dual RS485 And so on , On board Bluetooth、WIFI、4G（ Optional ） modular , At the same time lead to MIPI LCD、LVDS LCD、TFT LCD、CVBS OUT、CAMERA、LINE IN、H/P OUT Audio and video multimedia interface , Support dual screen display 、[email protected] H.264 Video hardware encoding and decoding , And support SATA Mass storage interface .

MQTT Introduction to communication protocol

summary

MQTT（Message Queuing Telemetry Transport, Message queuing telemetry transmission protocol ）, It's based on publishing / subscribe (Publish/Subscribe) Mode “ Lightweight ” Communication protocol , The agreement is built on TCP/IP Agreement on , from IBM stay 1999 Released in .MQTT The biggest advantage is , Very little code and limited bandwidth , Provide real-time and reliable message services for connecting remote devices .

MQTT It's lightweight 、 Simple 、 Open and easy to implement , At the same time, as a low cost 、 Low bandwidth instant messaging protocol , Make it in the Internet of things 、 Small equipment 、 Mobile applications are widely used .

chart 1

MQTT It has the following characteristics ：

Lightweight and reliable ：MQTT The message format is simplified 、 compact , Available in severely limited hardware devices and low bandwidth 、 Stable transmission over high latency networks .
Release / A subscription model (Publish/Subscribe)： Release / The advantage of the subscription model is the decoupling of publishers and subscribers , Implement asynchronous protocol . That is, subscribers and publishers do not need to establish a direct connection , There is no need to be online at the same time .
Born for the Internet of things ： Provide heartbeat mechanism 、 Will news 、QoS Quality grade + offline message 、 Comprehensive Internet of things application features such as theme and security management .
Better Ecology ： Wide coverage , It has become the standard communication protocol for many cloud manufacturers' Internet of things platforms .

Application scenarios

MQTT As a low cost , Low bandwidth instant messaging protocol , It can provide real-time and reliable message services for networked devices with very little code and bandwidth , It is suitable for devices with limited hardware resources and network environments with limited bandwidth . The common application scenarios are as follows ：

The Internet of things M2M signal communication , Internet of things big data collection .
Mobile instant messaging and message push .
Smart hardware 、 Smart home 、 Intelligent electrical apparatus .
Vehicle networking communication , Electric vehicle station pile collection .
Smart city 、 telemedicine 、 distance learning .
Electric energy 、 Petroleum Energy .

Mosquitto Tool installation

Mosquitto It's an open source MQTT The message broker （ The server ） Software , Offer lightweight 、 Support for releasable / Subscribable message push mode . The evaluation board file system provided by our company has supported Mosquitto Tools , this paper mqtt_client Case with Mosquitto Tool demonstration MQTT Communication function of communication protocol . Because the upper computer Ubuntu The system is the object of communication , Therefore, it is necessary to Ubuntu The terminal executes the following commands to install Mosquitto Tools .

Host# sudo apt-get install mosquitto-clients

chart 2

mqtt_client Case study

Case description

Case function ： Use libmosquitto(MQTT version 3.1.1 client library) Of API And MQTT Proxy server communication . be based on MQTT Communication protocol , Realize the function of publishing and subscribing to messages .

The program flow chart is shown in the following figure .

chart 3

Case test

This case uses the public network MQTT HiveMQ Server and upper computer Ubuntu Mosquitto Tool communication . Please connect the evaluation board to the Gigabit network port through the network cable RGMII ETH And the upper computer are connected to the public network , Ensure normal access to the Internet .

The following table provides the available online public MQTT The server , It can switch on its own as needed .

surface 1

Server name	Broker Address	TCP port	WebSocket
HiveMQ	broker.hivemq.com	1883	8000
Mosquitto	test.mosquitto.org	1883	80
Eclipse	mqtt.eclipseprojects.io	1883	80/443
EMQ X（ At home ）	broker-cn.emqx.io	1883	8083/8084

The evaluation board starts , The case bin Under the table of contents mqtt_client Copy the executable file to any directory of the evaluation board file system , Execute the following command to view the program parameter description .

Target# ./mqtt_client --help

chart 4

Evaluation board release / The upper computer subscribes

Execute the following commands on the upper computer , Use mosquitto_sub Tool subscription MQTT The theme .

Host# mosquitto_sub -h broker.hivemq.com -p 1883 -t test/data

Argument parsing ：

-h： Appoint MQTT The server ;

-p： Appoint MQTT The server TCP port ;

-t： Definition MQTT The theme , You can customize the name .

chart 5

Execute the following command in the evaluation board file system to publish a message to MQTT The server .

Target# ./mqtt_client -h broker.hivemq.com -p 1883 -M publish -t test/data -m 'www.tronlong.com'

chart 6 Evaluation board release

After the message is successfully published , The upper computer will start from MQTT The server receives the corresponding message .

chart 7 The upper computer subscribes

Evaluation board subscription / The upper computer releases

Execute the following command on the evaluation board file system to subscribe MQTT The theme .

Target# ./mqtt_client -h broker.hivemq.com -p 1883 -M subscribe -t test/data

chart 8

Execute the following commands on the upper computer to issue messages to MQTT The server .

Host# mosquitto_pub -h broker.hivemq.com -p 1883 -t test/data -m www.tronlong.com

chart 9 The upper computer releases

After the message is successfully published , The evaluation board will start from MQTT The server receives the corresponding message .

chart 10 Evaluation board subscription

Case compilation

The case src Copy the folder to Ubuntu Working directory , Please make sure you have referred to Linux The system user manual has been compiled LinuxSDK, structure T3 The processor corresponds to GCC compiler . Get into src The directory executes the following command , Use LinuxSDK Under the development package directory GCC Compiler for case compilation . After compilation , The executable will be generated in the current directory .

Host# CC=/home/tronlong/T3/lichee/out/sun8iw11p1/linux/common/buildroot/host/usr/bin/arm-linux-gnueabihf-gcc make

chart 11

Key code

establish Mosquitto example .

chart 12

Set the callback function .

chart 13

Connect MQTT The server .

chart 14

Release the news .

chart 15

Subscribe to topics .

chart 16

mqtt_sinewave_pub Case study

Case description

Case function ： Use libmosquitto(MQTT version 3.1.1 client library) Of API And MQTT Proxy server communication . Evaluation board generates sine wave data , Send... Every second 512 Data from sampling points to MQTT The server ; Upper computer passes Web Page from MQTT After the server receives the data , The waveform will be drawn .

The program flow chart is shown in the following figure .

chart 17

Case test

This case uses the public network MQTT HiveMQ Server and upper computer Ubuntu Web Program communication . Please connect the evaluation board to the Gigabit network port through the network cable RGMII ETH And the upper computer are connected to the public network , Ensure normal access to the Internet .

The evaluation board starts , The case bin Under the table of contents mqtt_sinewave_pub Copy the executable file to any directory of the evaluation board file system , Execute the following command to view the program parameter description .

Target# ./mqtt_sinewave_pub --help

chart 18

Execute the following command to run the program , Connect MQTT The server , And send sine wave data to MQTT The server .

Target# ./mqtt_sinewave_pub -h broker.hivemq.com -p 1883

chart 19

After the evaluation board program runs , The case "tools\web_mqtt_sub\" Under the table of contents index.html file , Use the upper computer browser to open . In the pop-up Web page （ Here's the picture ）, Input in sequence MQTT The server ：broker.hivemq.com, Port number ：8000, Finally, click Connect ,Web The page will start from MQTT The server obtains the sine wave data and draws the waveform .

remarks ：ARM End MQTT The communication protocol is based on TCP agreement ,Web End MQTT The communication protocol is based on WebSocket agreement , Therefore, different port numbers are used .