arduino库文件建立方法.docx
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arduino库文件建立方法
WritingaLibraryforArduino
ThisdocumentexplainshowtocreatealibraryforArduino.ItstartswithasketchforflashingMorsecodeandexplainshowtoconvertitsfunctionsintoalibrary.Thisallowsotherpeopletoeasilyusethecodethatyou'vewrittenandtoeasilyupdateitasyouimprovethelibrary.
Formoreinformation,seethe APIStyleGuide forinformationonmakingagoodArduino-styleAPIforyourlibrary.
WestartwithasketchthatdoessimpleMorsecode:
int pin = 13;
void setup（）
{
pinMode（pin, OUTPUT）;
}
void loop（）
{
dot（）; dot（）; dot（）;
dash（）; dash（）; dash（）;
dot（）; dot（）; dot（）;
delay（3000）;
}
void dot（）
{
digitalWrite（pin, HIGH）;
delay（250）;
digitalWrite（pin, LOW）;
delay（250）;
}
void dash（）
{
digitalWrite（pin, HIGH）;
delay（1000）;
digitalWrite（pin, LOW）;
delay（250）;
}
[GetCode]
Ifyourunthissketch,itwillflashoutthecodeforSOS（adistresscall）onpin13.
Thesketchhasafewdifferentpartsthatwe'llneedtobringintoourlibrary.First,ofcourse,wehavethe dot（） anddash（） functionsthatdotheactualblinking.Second,there'sthe ledPin variablewhichthefunctionsusetodeterminewhichpintouse.Finally,there'sthecallto pinMode（） thatinitializesthepinasanoutput.
Let'sstartturningthesketchintoalibrary!
Youneedatleasttwofilesforalibrary:
aheaderfile（w/theextension.h）andthesourcefile（w/extension.cpp）.Theheaderfilehasdefinitionsforthelibrary:
basicallyalistingofeverythingthat'sinside;whilethesourcefilehastheactualcode.We'llcallourlibrary"Morse",soourheaderfilewillbeMorse.h.Let'stakealookatwhatgoesinit.Itmightseemabitstrangeatfirst,butitwillmakemoresenseonceyouseethesourcefilethatgoeswithit.
Thecoreoftheheaderfileconsistsofalineforeachfunctioninthelibrary,wrappedupinaclassalongwithanyvariablesyouneed:
class Morse
{
public:
Morse（int pin）;
void dot（）;
void dash（）;
private:
int _pin;
};
[GetCode]
Aclassissimplyacollectionoffunctionsandvariablesthatareallkepttogetherinoneplace.Thesefunctionsandvariablescanbe public,meaningthattheycanbeaccessedbypeopleusingyourlibrary,or private,meaningtheycanonlybeaccessedfromwithintheclassitself.Eachclasshasaspecialfunctionknownasa constructor,whichisusedtocreatean instance oftheclass.Theconstructorhasthesamenameastheclass,andnoreturntype.
Youneedacoupleofotherthingsintheheaderfile.Oneisan#includestatementthatgivesyouaccesstothestandardtypesandconstantsoftheArduinolanguage（thisisautomaticallyaddedtonormalsketches,butnottolibraries）.Itlookslikethis（andgoesabovetheclassdefinitiongivenpreviously）:
#include"Arduino.h"
[GetCode]
Finally,it'scommontowrapthewholeheaderfileupinaweirdlookingconstruct:
#ifndefMorse_h
#defineMorse_h
//the#includestatmentandcodegohere...
#endif
[GetCode]
Basically,thispreventsproblemsifsomeoneaccidently#include'syourlibrarytwice.
Finally,youusuallyputacommentatthetopofthelibrarywithitsname,ashortdescriptionofwhatitdoes,whowroteit,thedate,andthelicense.
Let'stakealookatthecompleteheaderfile:
/*
Morse.h-LibraryforflashingMorsecode.
CreatedbyDavidA.Mellis,November2,2007.
Releasedintothepublicdomain.
*/
#ifndefMorse_h
#defineMorse_h
#include"Arduino.h"
class Morse
{
public:
Morse（int pin）;
void dot（）;
void dash（）;
private:
int _pin;
};
#endif
[GetCode]
Nowlet'sgothroughthevariouspartsofthesourcefile,Morse.cpp.
Firstcomesacoupleof#includestatements.ThesegivetherestofthecodeaccesstothestandardArduinofunctions,andtothedefinitionsinyourheaderfile:
#include"Arduino.h"
#include"Morse.h"
[GetCode]
Thencomestheconstructor.Again,thisexplainswhatshouldhappenwhensomeonecreatesaninstanceofyourclass.Inthiscase,theuserspecifieswhichpintheywouldliketouse.Weconfigurethepinasanoutputsaveitintoaprivatevariableforuseintheotherfunctions:
Morse:
:
Morse（int pin）
{
pinMode（pin, OUTPUT）;
_pin = pin;
}
[GetCode]
Thereareacoupleofstrangethingsinthiscode.Firstisthe Morse:
:
beforethenameofthefunction.Thissaysthatthefunctionispartofthe Morse class.You'llseethisagainintheotherfunctionsintheclass.Thesecondunusualthingistheunderscoreinthenameofourprivatevariable, _pin.Thisvariablecanactuallyhaveanynameyouwant,aslongasitmatchesthedefinitionintheheaderfile.Addinganunderscoretothestartofthenameisacommonconventiontomakeitclearwhichvariablesareprivate,andalsotodistinguishthenamefromthatoftheargumenttothefunction（pin inthiscase）.
Nextcomestheactualcodefromthesketchthatyou'returningintoalibrary（finally!
）.Itlooksprettymuchthesame,exceptwith Morse:
:
infrontofthenamesofthefunctions,and _pin insteadof pin:
void Morse:
:
dot（）
{
digitalWrite（_pin, HIGH）;
delay（250）;
digitalWrite（_pin, LOW）;
delay（250）;
}
void Morse:
:
dash（）
{
digitalWrite（_pin, HIGH）;
delay（1000）;
digitalWrite（_pin, LOW）;
delay（250）;
}
[GetCode]
Finally,it'stypicaltoincludethecommentheaderatthetopofthesourcefileaswell.Let'sseethewholething:
/*
Morse.cpp-LibraryforflashingMorsecode.
CreatedbyDavidA.Mellis,November2,2007.
Releasedintothepublicdomain.
*/
#include"Arduino.h"
#include"Morse.h"
Morse:
:
Morse（int pin）
{
pinMode（pin, OUTPUT）;
_pin = pin;
}
void Morse:
:
dot（）
{
digitalWrite（_pin, HIGH）;
delay（250）;
digitalWrite（_pin, LOW）;
delay（250）;
}
void Morse:
:
dash（）
{
digitalWrite（_pin, HIGH）;
delay（1000）;
digitalWrite（_pin, LOW）;
delay（250）;
}
[GetCode]
Andthat'sallyouneed（there'ssomeotherniceoptionalstuff,butwe'lltalkaboutthatlater）.Let'sseehowyouusethelibrary.
First,makea Morse directoryinsideofthe libraries sub-directoryofyoursketchbookdirectory.CopyormovetheMorse.handMorse.cppfilesintothatdirectory.NowlaunchtheArduinoenvironment.Ifyouopenthe Sketch>ImportLibrary menu,youshouldseeMorseinside.Thelibrarywillbecompiledwithsketchesthatuseit.Ifthelibrarydoesn'tseemtobuild,makesurethatthefilesreallyendin.cppand.h（withnoextra.pdeor.txtextension,forexample）.
Let'sseehowwecanreplicateouroldSOSsketchusingthenewlibrary:
#include
Morsemorse（13）;
void setup（）
{
}
void loop（）
{
morse.dot（）; morse.dot（）; morse.dot（）;
morse.dash（）; morse.dash（）; morse.dash（）;
morse.dot（）; morse.dot（）; morse.dot（）;
delay（3000）;
}
[GetCode]
Thereareafewdifferencesfromtheoldsketch（besidesthefactthatsomeofthecodehasmovedtoalibrary）.
First,we'veaddedan#includestatementtothetopofthesketch.ThismakestheMorselibraryavailabletothesketchandincludesitinthecodesenttotheboard.Thatmeansifyounolongerneedalibraryinasketch,youshoulddeletethe#includestatementtosavespace.
Second,wenowcreateaninstanceoftheMorseclasscalled morse:
Morsemorse（13）;
[GetCode]
Whenthislinegetsexecuted（whichactuallyhappensevenbeforethe setup（） function）,theconstructorfortheMorseclasswillbecalled,andpassedtheargumentyou'vegivenhere（inthiscase,just 13）.
Noticethatour setup（） isnowempty;that'sbecausethecallto pinMode（） happensinsidethelibrary（whentheinstanceisconstructed）.
Finally,tocallthe dot（） and dash（） functions,weneedtoprefixthemwith morse. -thenameoftheinstancewewanttouse.WecouldhavemultipleinstancesoftheMorseclass,eachontheirownpinstoredinthe_pinprivatevariableofthatinstance.Bycallingafunctiononaparticularinstance,wespecifywhichinstance'svariablesshouldbeusedduringthatcalltoafunction.Thatis,ifwehadboth:
Morsemorse（13）;
Morsemorse2（12）;
[GetCode]
theninsideacallto morse2.dot（）, _pin wouldbe12.
Ifyoutriedthenewsketch,youprobablynoticedthatnothingfromourlibrarywasrecognizedbytheenvironmentandhighlightedincolor.Unfortunately,theArduinosoftwarecan'tautomaticallyfigureoutwhatyou'vedefineinyourlibrary（thoughitwouldbeanicefeaturetohave）,soyouhavetogiveitalittlehelp.Todothis,createafilecalledkeywords.txt intheMorsedirectory.Itshouldlooklikethis:
Morse KEYWORD1
dash KEYWORD2
dot KEYWORD2
[GetCode]
Eachlinehasthenameofthekeyword,followedbyatab（notspaces）,followedbythekindofkeyword.Classesshouldbe KEYWORD1 andarecoloredorange;functionsshouldbe KEYWORD2 andwillbebrown.You'llhavetorestarttheArduinoenvironmenttogetittorecognizethenewkeywords.
It'salsonicetoprovidepeoplewithanexamplesketchthatusesyourlibrary.Todothis,createan examples directoryinsidethe Morse directory.Then,moveorcopythedirectorycontainingthesketch（let'scallit SOS）wewroteaboveintotheexamplesdirectory.（Youcanfindthesketchusingthe Sketch>ShowSketchFolder command.）IfyourestarttheArduinoenvironment（thisisthelasttime,Ipromise）-you'llseea Library-Morse iteminsidethe File>Sketchbook>Examples menucontainingyourexample.Youmightwanttoaddsomecommentsthatbetterexplainhowtouseyourlibrary.
Ifyou'dliketocheckoutthecompletelibrary（withkeywordsandexample）,youcandownloadit:
Morse.zip.
That'sallfornowbutI'llprobablywriteanadvancedlibrarytutorialsoon.Inthemeantime,ifyouhaveanyproblemsorsuggestions,pleas
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