【正文】 raised.Each barn has an intelligent node, which is based on STC89C52 microcontroller mainly plete the collection and processing of temperature and humidity inside the barn, anddisplay and make judgments on the overlimit alarm and No difference control. It also deliver the relevant information to PC by the CAN bus. Host puter find out each barn? s temperatures and humidity through the information ing from intelligent nodes, and set temperature and humidity alarm threshold in every ban based due to every intelligent node?s address, and therefore the problem on Multiple barn?s temperature and humidity monitor has been solved.In the end, the work in this paper is summarized and the further step of this research is clarified.Key Words: barn, temperature and humidity control, CANbus目 錄1 緒論 ............................................................................................................................ 1 背景....................................................................................................................... 1 國內(nèi)外研究現(xiàn)狀與發(fā)展趨勢............................................................................... 3 設(shè)計的目的及意義............................................................................................... 4 設(shè)計的主要工作................................................................................................... 5 本文的研究內(nèi)容................................................................................................... 52 方案選擇與總體設(shè)計 ................................................................................................ 6 溫濕度的相關(guān)概念............................................................................................... 6 溫濕度的測量方法............................................................................................... 8 溫濕度傳感器的選取........................................................................................... 9 系統(tǒng)總體設(shè)計..................................................................................................... 103 系統(tǒng)硬件設(shè)計 .......................................................................................................... 15 STC89C52 簡介.................................................................................................. 15 數(shù)據(jù)采集電路..................................................................................................... 16 DHT21 性能說明......................................................................................... 17 DHT21 引腳介紹......................................................................................... 18 DHT21 數(shù)據(jù)格式......................................................................................... 18 DHT21 時序................................................................................................. 18 鍵盤輸入電路..................................................................................................... 20 LCD 顯示電路 .................................................................................................... 21 電路概述 ...................................................................................................... 21 LCD1602 引腳 ............................................................................................. 21 LCD1602 控制器 ......................................................................................... 21 LCD1602 基本操作 ..................................................................................... 22 實時時鐘電路..................................................................................................... 23 電路及芯片概述 .......................................................................................... 23 DS1302 引腳 ................................................................................................ 23 DS1302 寄存器 ............................................................................................ 24 DS1302 控制字 ............................................................................................ 24 DS1302 時序 ................................................................................................ 25 掉電保護電路..................................................................................................... 26 CAN 總線通信.................................................................................................... 28 CAN 總線概述............................................................................................. 28 CAN 控制器 MCP2515 ............................................................................... 29 CAN 收發(fā)器 TJA1050 ................................................................................. 31 光電隔離器 6N137 ...................................................................................... 32 上位機與 CAN 的連接................................................................................ 33 下位機與 CAN 的連接................................................................................ 34 輸出控制電路..................................................................................................... 35 聲光報警電路..................................................................................................... 35 系統(tǒng)電源電路................................................................................................... 364 系統(tǒng)軟件設(shè)計 .......................................................................................................... 37 溫濕度設(shè)置......................................................................................................... 37 數(shù)據(jù)的采集與處理............................................................................................. 37 PWM 控制算法 .................................................................................................. 38 系統(tǒng)通信程序..................................................................................................... 39 人機界面設(shè)計....................................................