一只老鳥的(de)嵌入(ru)式系統基(ji)礎知識總結，嵌入(ru)式學習(xi)必看
時間：2018-06-05 來源：未知(zhi)
要學(xue)習嵌(qian)入(ru)(ru)式，那(nei)必不可少的(de)(de)就(jiu)要對嵌(qian)入(ru)(ru)式及嵌(qian)入(ru)(ru)式系統的(de)(de)基礎知(zhi)識(shi)要熟悉了解，分享一些我總結的(de)(de)一些嵌(qian)入(ru)(ru)式系統的(de)(de)基礎知(zhi)識(shi)，對你有用(yong)就(jiu)是王(wang)道。
嵌入式(shi)系統基(ji)礎(chu)(chu)知識我們首先(xian)(xian)要(yao)先(xian)(xian)分析(xi)一(yi)(yi)下(xia)，想要(yao)知道這個基(ji)礎(chu)(chu)知識，那我就應該(gai)要(yao)知道嵌入式(shi)系統是什(shen)么(me)呢，知道這個才可以進(jin)行下(xia)一(yi)(yi)個
什么是嵌入式系統
嵌入(ru)式(shi)(shi)系(xi)(xi)統(tong)(tong)(tong)是以(yi)(yi)(yi)應(ying)用(yong)為中(zhong)心(xin)，以(yi)(yi)(yi)計(ji)(ji)算機技(ji)術為基礎，軟硬件可裁剪，適應(ying)應(ying)用(yong)系(xi)(xi)統(tong)(tong)(tong)對功能、可靠性、成本(ben)、體積、功耗嚴格要求的(de)(de)(de)專用(yong)計(ji)(ji)算機系(xi)(xi)統(tong)(tong)(tong)。他(ta)的(de)(de)(de)核心(xin)就是有有一些微(wei)處(chu)理器或(huo)者單片機組成的(de)(de)(de)。他(ta)的(de)(de)(de)軟件通常是暫時不變(bian)的(de)(de)(de)，所以(yi)(yi)(yi)經(jing)常被稱為“固件”。我(wo)來(lai)做(zuo)個(ge)(ge)比(bi)喻，嵌入(ru)式(shi)(shi)系(xi)(xi)統(tong)(tong)(tong)就像(xiang)是人的(de)(de)(de)大(da)腦一樣，可以(yi)(yi)(yi)用(yong)來(lai)控制人的(de)(de)(de)手(shou)腳，或(huo)者監控一些病變(bian)，他(ta)就是這(zhe)樣一個(ge)(ge)系(xi)(xi)統(tong)(tong)(tong)。對于一些帶有數字接口的(de)(de)(de)設(she)備，如手(shou)表、微(wei)波爐、錄像(xiang)機、汽車等(deng)，都使(shi)用(yong)嵌入(ru)式(shi)(shi)系(xi)(xi)統(tong)(tong)(tong)，有些嵌入(ru)式(shi)(shi)系(xi)(xi)統(tong)(tong)(tong)還包(bao)含操(cao)作(zuo)系(xi)(xi)統(tong)(tong)(tong)，但大(da)多數嵌入(ru)式(shi)(shi)系(xi)(xi)統(tong)(tong)(tong)都是由單個(ge)(ge)程序實現整個(ge)(ge)控制邏輯(ji)。
一個嵌(qian)入式(shi)系(xi)統(本文所(suo)說的嵌(qian)入式(shi)系(xi)統包(bao)括ARM，DSP，單片機等(deng)，不(bu)包(bao)括FPGA、CPLD等(deng))的開發至少涉及到硬(ying)件和軟件兩個部分。
1、從(cong)硬(ying)件上，將基(ji)于(yu)CPU的(de)處圍(wei)器(qi)件，整(zheng)合到(dao)CPU芯片(pian)內部(bu)，比(bi)如(ru)早(zao)期(qi)基(ji)于(yu)X86體(ti)系結構下的(de)計算機，CPU只是有運算器(qi)和累加器(qi)的(de)功能，一切芯片(pian)要(yao)造外部(bu)橋(qiao)路來擴展實現(xian)，象(xiang)串(chuan)口之類的(de)都(dou)是靠外部(bu)的(de)16C550/2的(de)串(chuan)口控制器(qi)芯片(pian)實現(xian)，而(er)目(mu)前的(de)這種串(chuan)口控制器(qi)芯片(pian)早(zao)已集成到(dao)CPU內部(bu)，還(huan)有PC機有顯(xian)卡(ka)(ka)，而(er)多數(shu)嵌入式處理器(qi)都(dou)帶有LCD控制器(qi)，但其種意義上就相當于(yu)顯(xian)卡(ka)(ka)。
從軟件(jian)上講，就(jiu)是在定(ding)制操作系(xi)統內(nei)核(he)里將(jiang)應用(yong)一(yi)并(bing)選(xuan)入，編譯后(hou)將(jiang)內(nei)核(he)下載(zai)到(dao)ROM中。而在定(ding)制操作系(xi)統內(nei)核(he)時(shi)所選(xuan)擇的(de)(de)應用(yong)程序(xu)組件(jian)就(jiu)是完成了軟件(jian)的(de)(de)“嵌入”，比如WinCE在內(nei)核(he)定(ding)制時(shi)，會有相應選(xuan)擇，其(qi)中就(jiu)是Wordpad,PDF,MediaPlay等(deng)(deng)等(deng)(deng)選(xuan)擇，如果我們(men)選(xuan)擇了，在CE啟(qi)動(dong)后(hou)，就(jiu)可以在界面(mian)中找(zhao)到(dao)這些(xie)東(dong)西(xi)，如果是以前PC上將(jiang)的(de)(de)windows操作系(xi)統，多半的(de)(de)東(dong)西(xi)都需要我們(men)得(de)新再裝。
對(dui)上面這(zhe)(zhe)些概念是(shi)不(bu)(bu)是(shi)還是(shi)有點云里(li)霧里(li)的(de)，那我來舉個例子，讓你更清楚的(de)了解，硬件之(zhi)數(shu)字(zi)電路：就比如CPU的(de)外圍電路，晶振，復(fu)位(wei)，擴展(zhan)的(de)eeprom等等，都(dou)(dou)不(bu)(bu)需(xu)(xu)要我們設計，直接根據(ju)芯片(pian)手(shou)冊上的(de)典型應用連接即(ji)可(ke)(ke)，變化也很少。但是(shi)如果要讓這(zhe)(zhe)些芯片(pian)工作起來，開發者需(xu)(xu)要讀懂用戶手(shou)冊，重點看操(cao)作芯片(pian)的(de)流程圖(tu)和時序圖(tu)。電路和數(shu)字(zi)電路都(dou)(dou)很簡(jian)單，不(bu)(bu)需(xu)(xu)要刻(ke)意去(qu)學習，更不(bu)(bu)需(xu)(xu)要多深入。只需(xu)(xu)要認識(shi)高低電平即(ji)可(ke)(ke)。這(zhe)(zhe)是(shi)硬件的(de)簡(jian)單介紹。
那(nei)軟件(jian)方面的話(hua)，我舉(ju)個例子，就是(shi)C語言(yan)的學習了(le)，C語言(yan)功底一定(ding)要(yao)好，結(jie)構體，指(zhi)針(zhen)等(deng)需要(yao)熟(shu)練使用。嵌(qian)入式說白(bai)了(le)就是(shi)用C語言(yan)操作硬件(jian)，C語言(yan)的水平(ping)決定(ding)了(le)程序的效率。無(wu)論如何，C語言(yan)一定(ding)要(yao)學好。且不推(tui)薦匯編語言(yan)。
以上為嵌入式硬件(jian)與軟件(jian)的一些基礎知識，這(zhe)還遠遠不(bu)夠，重(zhong)頭戲(xi)來了：
嵌(qian)(qian)入(ru)式(shi)(shi)系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)(tong)一般由嵌(qian)(qian)入(ru)式(shi)(shi)微處(chu)理(li)器(qi)、外圍硬件(jian)設備(bei)、嵌(qian)(qian)入(ru)式(shi)(shi)操(cao)作系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)(tong)和應用(yong)(yong)程序組成，用(yong)(yong)于對其他設備(bei)的控(kong)(kong)(kong)(kong)制(zhi)(zhi)和監視或(huo)管(guan)理(li)等功能。應用(yong)(yong)舉(ju)例汽車(che)中嵌(qian)(qian)入(ru)式(shi)(shi)系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)(tong)包括，電(dian)(dian)子(zi)(zi)控(kong)(kong)(kong)(kong)制(zhi)(zhi)裝置(zhi)：車(che)燈控(kong)(kong)(kong)(kong)制(zhi)(zhi)，車(che)窗控(kong)(kong)(kong)(kong)制(zhi)(zhi)，門鎖集中控(kong)(kong)(kong)(kong)制(zhi)(zhi)，空調控(kong)(kong)(kong)(kong)制(zhi)(zhi)，電(dian)(dian)控(kong)(kong)(kong)(kong)剎(cha)車(che)，ABS控(kong)(kong)(kong)(kong)制(zhi)(zhi)，安全氣囊控(kong)(kong)(kong)(kong)制(zhi)(zhi)，發(fa)動(dong)(dong)機(ji)控(kong)(kong)(kong)(kong)制(zhi)(zhi)，AT控(kong)(kong)(kong)(kong)制(zhi)(zhi)(自動(dong)(dong)變(bian)速(su)器(qi))。自動(dong)(dong)泊車(che)系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)(tong)，自動(dong)(dong)巡航(hang)(hang)系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)(tong)，夜視系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)(tong)，自動(dong)(dong)駕駛。車(che)載(zai)電(dian)(dian)子(zi)(zi)裝置(zhi)：導航(hang)(hang)系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)(tong)，汽車(che)音響(xiang)，電(dian)(dian)子(zi)(zi)娛樂系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)(tong)，車(che)載(zai)通信系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)(tong)。
嵌入式最小硬件(jian)系統(tong)，嵌入式處理器，時鐘(zhong)電(dian)路，電(dian)源(yuan)電(dian)路，復位電(dian)路，存儲器，調試測試接口。前向通道(dao)，后向通道(dao)，人機交互(hu)(hu)通道(dao)，相互(hu)(hu)互(hu)(hu)聯通道(dao)，最小系統(tong)。
嵌(qian)入式處理器由存儲器、I/O設備(bei)、通(tong)信模塊(USB、UART、以(yi)太網、Iic、CAN、)和電源等組(zu)成。
嵌(qian)入式系(xi)統(tong)(tong)開發流程：需求分析->體(ti)系(xi)結構設(she)(she)計(ji)->機械系(xi)統(tong)(tong)設(she)(she)計(ji)、硬件設(she)(she)計(ji)、軟件設(she)(she)計(ji)->系(xi)統(tong)(tong)集成->系(xi)統(tong)(tong)測試。
嵌入(ru)式系統(tong)軟(ruan)(ruan)件(jian)結(jie)構(gou)：簡(jian)(jian)單輪詢(xun)結(jie)構(gou)(簡(jian)(jian)單循環，數(shu)字萬(wan)用(yong)(yong)表)，帶中斷的(de)輪詢(xun)結(jie)構(gou)(有中斷，洗衣機(ji))，監控式操(cao)作(zuo)系統(tong)+應用(yong)(yong)軟(ruan)(ruan)件(jian)的(de)結(jie)構(gou)(內核+多(duo)任(ren)務，車(che)載(zai)設(she)備)，通用(yong)(yong)嵌入(ru)式操(cao)作(zuo)系統(tong)+應用(yong)(yong)軟(ruan)(ruan)件(jian)的(de)結(jie)構(gou)(常(chang)用(yong)(yong)操(cao)作(zuo)系統(tong)+中間(jian)件(jian)+應用(yong)(yong)軟(ruan)(ruan)件(jian)，手機(ji))。
設(she)備驅動(dong)程(cheng)序：設(she)備的初(chu)始化(hua)，設(she)備的打開和(he)關閉，設(she)備的讀取(qu)和(he)寫(xie)入(ru)，設(she)備狀(zhuang)態的查詢和(he)設(she)備控制操作。
內核(he)(he)結構(gou)分為單內核(he)(he)和(he)微(wei)內核(he)(he)。單內核(he)(he)將各個模塊整(zheng)合在一起，模塊間(jian)的(de)(de)相互通(tong)信(xin)通(tong)過直接調用(yong)其他模塊的(de)(de)函數(shu)來(lai)實(shi)現，分為整(zheng)體結構(gou)和(he)分層結構(gou)。微(wei)內核(he)(he)僅將必須的(de)(de)基本功能(任務調度、任務間(jian)通(tong)信(xin)、低級存儲(chu)管理(li)(li)、中斷處(chu)理(li)(li)等(deng))放入內核(he)(he)，其他功能(文件管理(li)(li)服(fu)(fu)務、網絡通(tong)信(xin)服(fu)(fu)務、顯示(shi)服(fu)(fu)務等(deng))由在用(yong)戶運行的(de)(de)服(fu)(fu)務來(lai)實(shi)現。
所以(yi)嵌(qian)入式(shi)系統(tong)的(de)(de)(de)學(xue)習(xi)(xi)還是(shi)需要你把這(zhe)些(xie)都(dou)掌握好，只(zhi)有對這(zhe)些(xie)都(dou)了解，你才(cai)能進(jin)行(xing)對嵌(qian)入式(shi)進(jin)一步的(de)(de)(de)研究，這(zhe)些(xie)都(dou)是(shi)我(wo)學(xue)習(xi)(xi)過程(cheng)中(zhong)總結的(de)(de)(de)，可以(yi)學(xue)習(xi)(xi)借(jie)鑒(jian)哦(e)。還有不妨可以(yi)看(kan)看(kan)嵌(qian)入式(shi)學(xue)習(xi)(xi)路線，讓你的(de)(de)(de)思路更加的(de)(de)(de)清楚。
