LED驱动器和一个4x4键盘采样复用

ManyapplicationsrequiredrivingLEDsalongwithan

interfacetoakeypad.Implementingsuchdesigns

usuallyinvolvesusingupsignificantamountsofthe

processorsI/Olines.Thisapplicationnotedescribesa

methodwhichusesonly16I/OpinsofaPIC16C5X

microcontrollertosamplea4x4keypadmatrix,and

directlydrivefour7-segmentLEDs(Figure1).AN529MultiplexingLEDDriveanda4x4KeypadSamplingdriveoftheLEDsispossible,becauseofthehighsinkAuthor:StanD’SouzaandsourcecapabilitiesofPIC16C5Xmicrocontroller,MicrochipTechnologyInc.thuseliminatingtheuseofanexternaldrivetransistor,andresultsinareductioninbothcostandcomplexityofINTRODUCTIONtheoverallcircuit.TypicallyapplicationshavingLEDsa