{"componentChunkName":"component---src-templates-blog-detail-tsx","path":"/blog/2019-07-04-online-formaldehyde-monitoring-system","result":{"data":{"currentBlog":{"id":"d6260dcf-6000-54c1-82c8-1e96f13d0f2b","frontmatter":{"thumbnail":"https://img.serverlesscloud.cn/qianyi/b96CibCt70iaaJcib7FH02wTKvoHALAMw4f553WgrmrmItKmjkMfO2fI0YJcpdO2WibwHXYAOGZyMaQruxD3skk7icQ.jpg","authors":["ecky"],"categories":["user-stories"],"date":"2019-07-04T00:00:00.000Z","title":"基于「树莓派+腾讯云」的在线甲醛监测系统","description":"本文详述腾讯云多产品组合设计和体验报告 之 “树莓派+腾讯云=在线甲醛监测系统”。涉及腾讯云产品：API网关、无服务器云函数、云数据库、腾讯云图。","authorslink":["https://zhuanlan.zhihu.com/ServerlessGo"],"translators":null,"translatorslink":null,"tags":["树莓派","Serverless"],"keywords":"Serverless,serverless framework,腾讯云serverless","outdated":null},"wordCount":{"words":378,"sentences":118,"paragraphs":118},"fileAbsolutePath":"/opt/build/repo/content/blog/2019-07-04-online-formaldehyde-monitoring-system.md","fields":{"slug":"/blog/2019-07-04-online-formaldehyde-monitoring-system/","keywords":["go","java","python","serverless","无服务器","无服务器云函数","云函数","javascript","serverlesscloud"]},"html":"

扔掉小瓶盖，腾讯云带你体验在线甲醛监测系统！本文详述腾讯云多产品组合设计和体验报告 之 “树莓派+腾讯云=在线甲醛监测系统”。涉及腾讯云产品：API网关、无服务器云函数、云数据库、腾讯云图。

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正文

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身边朋友在装修新房，顺便来吐槽甲醛检测麻烦，比如 有检测无监测（一次性），比如测试复杂（现场+人工）等等。刚好做为云产品经理，经常想的就是如何了解和验证多云产品组合方案的可用性问题，索性结合一下，直接把这个需求上云，然后就有了这套系统。老规矩，先上结论。

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系统概要

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产品设计特性

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系统组成

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终端：终端组件

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注：RaspberryPi后续简写为Rpi

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云端：腾讯云产品

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效果展示

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腾讯云图

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终端组件

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当前版本中，Rpi 使用wifi 连接互联网（也可使用有线网），故此处上云有网络依赖。

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传感器原理与功能定位

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UART-CH2O传感器

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设计与实现

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产品设计与技术策略

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设计过程中，也进行了产品生命周期的思考，尝试进行了产品长短期设计的分析与定义（暂不展开，后续有时间写一下）。

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确认了形态目标后，遵循下面几个基本原则，进行具体技术设计：

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概要架构图

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从架构看来

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分级可用目标

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4.本地实时展示+本地缓存+数据上云 +云端显示。

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3.本地实时展示+本地缓存+数据上云。云图异常。

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2.本地实时展示+本地缓存。上云通路异常。

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1.本地实时展示。本地sqlite异常。

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0.本地无展示。硬件故障或断电。

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硬件接线与打开系统接口

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Rpi GPIO

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GPIO

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(General-purpose input/output)即通用IO接口，是一种常见的端口扩展器，树莓派使用的是40针的GPIO接口。

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RPI GPIO图示

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UART-CH2O

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注：本次使用传感器，硬件接口是1.25mm端子，Rpi是2.5mm端子，使用了 7P1.25转2.5杜邦线，进行连接

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OLED

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接线方式(I2C协议)

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打开I2C接口

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raspi-config
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按下图打开I2C接口

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测试执行

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i2cdetect -y 1
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看到 3C 即识别硬件成功

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本地开发与配置

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本文暂仅放出关键代码(硬件操作部分)，便于大家撸硬件。完整包(代码+配置) 稍后放出，请关注 github/DemoOnTencentCloud。

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环境配置

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  • 启动对时：rc.local 增加 nptdata cn.ntp.org.cn。避免重启后时间错位，监测错位。
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  • 启动拉起：getdata.py oled.py 需持续在线。
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  • 定时检测：getdata.py oled.py cron每分钟判断活性，进程挂掉即拉起。
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  • 定时同步：sync.py cron每分钟执行
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  • 远程维护：使用ssh tunnel 的 Remote Port Forwarding 模式，进行反向代理。
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ssh tunnel

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此处使用 autossh 进行连接，autossh可完成建立通道与监控通道的工作，通道断开后，可自主重连。远端连接云主机，之后可以云主机为跳板，反向代理访问NAT环境Rpi设备。

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bash autossh -M 监控端口 -R 远程通信端口:localhost:22 账号名@远程IP或域名 -p端口号 -i 账号KEY -o serveraliveinterval=60 -N -f
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连接时，在云主机执行

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bash ssh -p 远程通信端口 localhost
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getdata.py

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获取传感器读数代码（完整代码待放出 github/DemoOnTencentCloud）

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import serial\nfrom time import sleep\n\nser=serial.Serial(\"/dev/serial0\",9600)\n\nwhile True :\n    r_data = ser.read()\n    sleep(0.3)\n    data_left = ser.inWaiting()\n    r_data += ser.read(data_left)\n    if 9 != len(r_data):\n        print 'error length: %d'%len(r_data)\n        continue\n    else:\n        n=ord(r_data[4])*256+ord(r_data[5])\n        updatedata(n/1000.0) # ppm = n/1000.0
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flusholed.py

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依赖库安装

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(基于 https://github.com/adafruit/Adafruit\\_Python\\_SSD1306)

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sudo python -m pip install --upgrade pip setuptools wheel\nsudo pip install Adafruit-SSD1306
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下为功能伪代码。（完整代码待放出 github/DemoOnTencentCloud）

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# 读取 cachefile 缓存文件\n# 刷新 OLED 显示
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sync.py

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下为功能伪代码。（完整代码待放出 github/DemoOnTencentCloud）

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# 访问 APIGW，获取最新记录时间戳\n# 读本地sqlite库，获取增量数据\n# 访问 APIGW，提交更新数据
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Sqlite结构

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表结构

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CREATE TABLE \"sensordata\" (\n\"id\" INTEGER PRIMARY KEY AUTOINCREMENT,\n\"utime\" INTEGER NOT NULL,\n\"utype\" INTEGER DEFAULT 0 NOT NULL,\n\"udata\" REAL NOT NULL,\n\"sdata\" TEXT\n);
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云端开发与配置

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无服务器云函数

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优先配置 无服务器云函数，参考 文档 建立并保存“函数代码”后，在管理页面的“触发方式”功能中，直接生成对应API网关。

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（完整代码待放出 github/DemoOnTencentCloud）。

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当前主要强调几个注意事项：

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  1. 自动提交：连接数据库必须使用“autocommit = True,”参数，否则由于事务隔离，DB链接重新连接前，查询结果不变。（查不到新增记录ID）
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  2. 返回头：API网关开启“响应集成”时，云函数返回值需结合返回信息，指定\"Content-Type\"，否则出现 \"transfer closed with outstanding read data remaining\" 错误。
    3. \n
  3. 验证连接：云函数实例可长期存在，但一定时间未操作mysql链接时，mysql将释放链接，所以代码中需要进行验证链路可用性。
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API网关

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配置服务

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参考 文档 ，以上“触发方式”中建立的API网关服务，由API网关的 服务 页面，点击相应服务名，选择“API管理”分页，点击“编辑”，然后配置“请求方法-POST”、“鉴权类型-密钥对”、“使用响应集成”，其它余配置按默认即可。

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下载与使用SDK

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API网关 控制台 -> 点击 服务名 -> 点击 API文档/SDK -> 点击 下载SDK

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（完整配置待放出 github/DemoOnTencentCloud）

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云数据库 Mysql

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表结构

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SET SQL_MODE = \"NO_AUTO_VALUE_ON_ZERO\";\nSET AUTOCOMMIT = 0;\nSTART TRANSACTION;\nSET time_zone = \"+00:00\";\n\nCREATE TABLE `sensordata` (\n  `id` int(11) NOT NULL,\n  `stime` timestamp NULL DEFAULT NULL,\n  `utype` int(11) NOT NULL DEFAULT '0',\n  `udata` float NOT NULL,\n  `sdata` varchar(256) DEFAULT NULL\n) ENGINE=InnoDB DEFAULT CHARSET=utf8;\n\nALTER TABLE `sensordata`\n  ADD PRIMARY KEY (`id`);\n\nALTER TABLE `sensordata`\n  MODIFY `id` int(11) NOT NULL AUTO_INCREMENT;\nCOMMIT;
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云图配置

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简要使用说明

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拖选组件 -> 点击数据栏 -> 选择数据库 -> 填写SQL -> 开启自动更新 -> 预览 -> 发布

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操作示例图

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组件配置信息

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  • 最新同步时间 - 通用文本
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select concat('最新同步时间 ',stime) as value from sensordata order by id desc limit 1
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  • 国标系数比 - 水位图
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select round((udata)/0.08*100, 2) as value from sensordata order by id desc limit 1
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  • 实时读数 - 基本条形图
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select round(udata, 3) as x, '' as y from sensordata order by id desc limit 1
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  • 10分钟数据 - 基本折线图
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select * from (select id, round(udata, 3) as y, date_format(stime, '%H:%i:%S') as x, utype as s from sensordata order by id desc limit 360) as t1 order by id asc
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  • 7天数据 - 基本折线图
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select distinct (dt), round(AVG(udata),3) as y, dt as x, '0' as s from (select id, date_format(stime, '%Y-%m-%d %H') as dt, udata from sensordata order by id desc limit 604800) as t1 group by dt order by dt ASC
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写在最后

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关于丢数据（非守护进程）、脏数据（未较验数据唯一性）、缺乏系统监控告警（未接入云监控）等等待优化点，由于时间关系暂未展开，后面可以再行探讨。

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传送门：

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欢迎访问：Serverless 中文网，您可以在 最佳实践 里体验更多关于 Serverless 应用的开发！

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