原创 通过网络远程控制ARM系统GPIO应用实例

1). 简介

本文着重展示基于Embedded Linux快速开发Web应用程序访问ARM系统以便于远程操控硬件GPIO或监控其状态.文中演示实例所采用的ARM系统硬件为Toradex 基于NXP Vybrid的产品级ARM核心板Colibri VF61配合其Colibri开发板;软件框架为使用Node代码通过filesystem来访问操控硬件GPIO,创建一个简单UI并使用Express开发框架搭建一个最简web服务器并通过AJAX呼叫和客户端进行通信,最后在客户端使用Javascript配合HTML+CSS/jQuery/AJAX开发一个客户端应用程序.

Node.js是一个用于基于Javascript开发应用的服务器端的runtime环境,自带有管理文件系统模块,而Linux操作系统支持使用文件系统访问硬件设备的特性,因此可以基于Node开发应用来访问操控系统硬件GPIO设备.不过尽管Node也提供了如HTTP等模块可以用来搭建Web服务器,本文还是采用更为简单的利用Express开发框架来搭建.

客户端应用使用Javascript编程语言开发,通过浏览器执行.配合HTML和CSS, Javascript可以实现用户交互的网页开发,也就是响应式设计. 不过直接使用Javascrit进行开发需要一定周期,本文采用一个跨浏览器JavaScript库jQuery来快速实现如DOM操作,事件处理以及AJAX方法(和服务器异步通讯达到动态改变页面内容的一系列技术)使用等

2). 硬件准备

a). Colibri VF61核心板模块以及Colibri开发板载板

b). GPIO以及对应Button和LED设置如下所示, VF61最多支持99个GPIO管脚, 本文使用4个GPIO分别连接Colibri载板上面的两个Button和两个LED.

SW5, X21 Pin9 <-> GPIO-63(SODIMM_106), X11 Pin39

SW6, X21 Pin11 <-> GPIO-89(SODIMM_135), X11 Pin40

LED1, X21 Pin2 <-> GPIO-88(SODIMM_133), X11 Pin41

LED2, X21 Pin4 <-> GPIO-68(SODIMM_127), X11 Pin42

详细的关于管脚定义和GPIO号码请参考VF61手册,Colibri开发板手册以及GPIO号码映射.

3). 软件配置

a). Embedded Linux系统为Toradex官方发布image V2.5, 也可以参考这里基于OpenEmbedded框架自己编译系统image.

b). 在VF61 Embedded Linux中安装node.js并验证运行正常

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root@colibri-vf:~# opkg update

root@colibri-vf:~# opkg install nodejs

root@colibri-vf:~# node                                                        

> process.exit ()                                                               

root@colibri-vf:~#

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c). 在VF61 Embedded Linux中安装nodemon, Express和body-parse

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root@colibri-vf:~# opkg install tar

root@colibri-vf:~# curl -L https://www.npmjs.com/install.sh | sh

root@colibri-vf:~# npm install express

root@colibri-vf:~# npm install body-parser       

root@colibri-vf:~# npm install -g nodemon

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4). GPIO操作

详细Embedded Linux GPIO操作请见这里,下面只用一个GPIO-63举例

a). 初始化GPIO-63并设置为Input

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root@colibri-vf:/sys/class/gpio# echo 63 > /sys/class/gpio/export              

root@colibri-vf:/sys/class/gpio# echo "in" > /sys/class/gpio/gpio63/direction

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b). 查看当前GPIO-63电平

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root@colibri-vf:/sys/class/gpio/gpio63# cat /sys/class/gpio/gpio63/value       

0

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c). 按下GPIO连接的Button同时查看电平

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root@colibri-vf:/sys/class/gpio/gpio63# cat /sys/class/gpio/gpio63/value       

1

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5). Nodedemo1  - 使用Node.js操控GPIO

完整代码请见这里, 需创建’server.js’文件, 核心部分列出如下:

a). Filesystem 模块

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/* Modules */

var fs = require('fs'); //module to handle the file system

var debug = require('debug')('myserver'); //debug module

 

/* VF61 GPIO pins */

const         SW5 = '63', // PTD31, 106(SODIMM)

         SW6 = '89', // PTD10, 135(SODIMM)

        LED1 = '88', // PTD9, 133(SODIMM)

         LED2 = '68', // PTD26, 127(SODIMM)

        

/* Constants */

const HIGH = 1, LOW = 0;

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b). GPIO配置和操作模块

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function cfGPIO(pin, direction){......}  //export pin if not exported and configure the pin direction

function rdGPIO(pin){......}  //read GPIO value and return it

function wrGPIO(pin, value){......}  //write value to corresponding GPIO

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c). LED根据Button状态显示模块

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function copySwToLed(){......} //Copy the SW values into the LEDs

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主函数模块,使用setinterval循环函数,第二个参数为循环间隔

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setImmediate(function cfgOurPins(){

         cfGPIO(LED1, 'out'); //call cfGPIO to configure pins

         cfGPIO(LED2, 'out');

         cfGPIO(SW5, 'in');

         cfGPIO(SW6, 'in');

         setInterval(copySwToLed, 50); //poll the GPIO and copy switches status to LEDs

});

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d). 在VF61上面执行’server.js’, 并通过按键来验证LED显示

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node server.js

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6). Nodedemo2 - 创建webserver和最简web UI来远程操控GPIO

完整代码请见这里

a). 修改’server.js’, 创建Webserver

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/* Modules */

var express = require('express'); //webserver module

var bodyParser = require('body-parser'); //parse JSON encoded strings

var app = express();

/* Constants */

const HIGH = 1, LOW = 0, IP_ADDR = '10.20.1.108', PORT_ADDR = 3000;

//Using Express to create a server

app.use(express.static(__dirname));

var server = app.listen(PORT_ADDR, IP_ADDR, function () {

    var host = server.address().address;

    var port = server.address().port;

    var family = server.address().family;

    debug('Express server listening at http://%s:%s %s', host, port, family);

});

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b). 修改’server.js’, 增加HTTP POST接收并处理返回数据部分

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app.use(bodyParser.urlencoded({ //to support URL-encoded bodies, must come before routing

         extended: true

}));

 

app.route('/gpio') //used to unite all the requst types for the same route

.post(function (req, res) { //handles incoming POST requests

        var serverResponse = {status:''};

        var btn = req.body.id, val = req.body.val; // get the button id and value

 

        if(val == 'on'){ //if button is clicked, turn on the leds

           wrGPIO(LED1, HIGH);

           wrGPIO(LED2, HIGH);

                debug('Client request to turn LEDs on');

           serverResponse.status = 'LEDs turned on.';

           res.send(serverResponse); //send response to the server

        }

        else{ //if button is unclicked, turn off the leds

           wrGPIO(LED1, LOW);

            wrGPIO(LED2, LOW);

            debug('Client request to turn LEDs off');

            serverResponse.status = 'LEDs turned off.';

            res.send(serverResponse); //send response to the server

        }

});

setImmediate(function cfgOurPins(){

         ......

    setInterval(copySwToLed, 50); //poll the GPIO and copy switches status to LEDs

});

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c). 在当前文件夹创建’index.html’

./ 请从这里下载jQuery库并放在同一文件夹

./ ‘index.html’代码如下

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<!DOCTYPE html>

<html>

<head>

         <meta charset="UTF-8">

         <title>Colibri VF61 node.js webserver</title>

         <!-- Add jQuery library -->

         <script src="jquery-1.12.3.js"></script>

         <script type="text/javascript" src="client.js"></script>

</head>

 

<body>

         <h1>Access to the VF61 GPIO using Node.js and AJAX</h1>

         <form>

                   <input type="checkbox" class="btn" id="btn1">

                   <label for="btn1" id="btn1l" style="color:red">OFF</label>

         </form>

</body>

</html>

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d). 在当前文件夹创建’client.js’, 用来处理客户端操作

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$(function(){

         $(".btn").click(function clickHandling(){ //if element of class "btn" is clicked

                   var btn_status = {id:"", val:""}; //data to be sent to the server

                  

                   if(this.checked){ //check whether button is pressed or not

                            $(this).siblings().html("ON").css("color","green"); //changes label and color

                            btn_status.id = $(this).attr("id"); //get which button was clicked

                            btn_status.val = "on"; //tell the server the button is clicked

                   }

                  

                   else{ //if button was unclicked

                            $(this).siblings().html("OFF").css("color","red"); //changes label and color

                            btn_status.id = $(this).attr("id"); //get which button was clicked

                            btn_status.val = "off"; //tell the server the button is unclicked

                   }

                  

                   $.post("/gpio", btn_status, function (data, status){ //send data to the server via HTTP POST

                            if(status == "success"){ //if server responds ok

                                     console.log(data);//print server response to the console

                            }

                   },"json"); //server response shuld be in JSON encoded format

         });

});

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e). 在VF61运行’server.js’, 启动服务

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root@colibri-vf:~# DEBUG=myserver node server.js                               

  myserver Starting VF61 GPIO control +0ms                                     

  myserver Express server listening at http://10.20.1.108:3000 IPv4 +711ms     

  myserver Configuring GPIO88 as out +46ms                                     

  myserver Configuring GPIO68 as out +9ms                                      

  myserver Configuring GPIO63 as in +3ms                                        

  myserver Configuring GPIO89 as in +2ms

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f). 在客户端浏览器查看

登录http://10.20.1.108:3000,在打开的页面操作checkbox来控制LED灯

 

7). Nodedemo3 - 升级友好界面客户端UI来远程操控GPIO

完整代码请见这里

a). 修改’index.html’, 使用Bootstrap框架修改显示效果适配移动设备

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         <!-- Using bootstrap -->

         <link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" integrity="sha384-1q8mTJOASx8j1Au+a5WDVnPi2lkFfwwEAa8hDDdjZlpLegxhjVME1fgjWPGmkzs7" crossorigin="anonymous">

         <script. src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js" integrity="sha384-0mSbJDEHialfmuBBQP6A4Qrprq5OVfW37PRR3j5ELqxss1yVqOtnepnHVP9aJ7xS" crossorigin="anonymous"></script>

         <script. type="text/javascript" src="client.js"></script>

</head>

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b). 对应修改’server.js’和’client.js’

 SW 按键点击事件处理, SW1切换当前LED焦点, SW2改变当前LED状态

c). 在VF61上面同上运行server.js启动,在客户端浏览器登录http://10.20.1.108:3000查看