电机驱动板讲解

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1、UnderstandingtheAdafruitMotorShie...UnderstandingtheAdafruitMotorShieldLibraryI'verecentlybeenworkingonasmallroboticsprojectusingtheArduinoplatformwiththeAdafruitmotorshield.I'manexperiencedapplicationsprogrammerbutacompletenoviceatelectronicsandembeddedprogramming,soIfinditchallengingtou

2、nderstandhowthehardwaredesignandthecoderelatetoeachother.I'vebeengoingthroughthemotorshieldschematicandthecodelibrarytotrytounderstandthembothindetail,andIthoughtitmightbehelpfultootherbeginningArduinistsifIweretowriteupwhatI'vefiguredoutsofar.AtleastfornowIwillfocusonDCmotorcontrolbecaus

3、ethat'swhatI'vebeenworkingonandhavelearnedthemostabout.BasicDCMotorControlLet'ssetasidespeedcontrolforamomentandfirstwalkthroughhowthemotorsareturnedonandoff.TheMotorDriversandShiftRegisterThemotorshieldcancontroluptofourDCmotorsusingtwoL293DdualH-bridgemotordriverICs.Youcanreadthedatashe

4、etfordetails,butthemainthingtoknowisthateachIChasfourdigitalinputsandcancontroltwomotorsbidirectionally.Theinputsareinpairs,andeachpaircontrolsamotor.Forexample,ifpin2issethighandpin7issetlow,motor1isturnedon.Iftheinputsarereversed,themotorisagainonbutitsdirectionofrotationisreversed,andi

5、fbotharesetlowthenthemotorisoff.Thereareotherpossibleconfigurationsbutthisistheonesupportedbythemotorshield.SoobviouslythethingtodoiswireeightpinsfromtheArduinototheeightinputsonthetwoICs,right?That'swhatIimaginedatfirst,butit'sWRONG!!Pinsareascarceresource,andthemotorshielddesignmakesane

6、xtraefforttoconservethem.Theinputstothemotordriversareactuallywiredtotheoutputsofa74HCT595N8-bitshiftregister.ThisICletsyoufeedinbitsserially,butitthenpresentsthemasparalleloutputs.It'scontrolledbyfourdigitalinputs,soeffectivelyitletsyoucontroleightinputstothemotordrivers(thusfourmotors)u

7、singfourpinsoftheArduino.Atthispointwecanstarttolookatcode.HerearesomeconstantsdefinedinAFMotor.h:#defineMOTOR1_A2#defineMOTOR1_B3#defineMOTOR2_A1#defineMOTOR2_B4#defineMOTOR4_A0#defineMOTOR4_B6#defineMOTOR3_A5#defineMOTOR3_B7Clearly,MOTOR1_AandMOTOR1_Bhavetodowithc