Page 62 - Making PIC Microcontroller Instruments and Controllers

52 CO TNOLIING TI'IE OUTPUTAND READITG THE INPUI

,t:1 .ji6!iil:5;2:l Blinking eighl LEDS one aller lhe other on a bargraph
CLEAR
DEFIAIE OSC 4
LED-ID VA.R BYTE calL ouL the two variables
A VTR BYTE
TRISD =%00000000 ser PoRTD to a1L ourpurs

IIAINLOOP: this loop is executed forever
initialize Lhe counter to 1
F o R t E D t D = 1 T O I do it for the I LEDS
PORTD=A puts nunDer a. PURrU
PAUSE 1OO pause so you can see the display
nuLtipLy by 2 noves liL I-ED left 1

NEXT IJED ID go up and increnent counter
GO!!O MAIIIITOOP do it aLl forever
END always end with END

Dim and Brishten One LED

In Program 5.3, we demonstrate |hc ability to dim an LED (at PORTD.O) by larying
the duty cycle ofthe ON signal to the LED.

Turns on an LED and dims the one next to it (Doing il this wav leis
tlB!!0iai!.riltqiSil
the brightness ofthe two LEDS)
you compare
' . - L E a D
CLEAR r i 5 d > " o f 6 0 5 .
DEFINE OSC 4
ERISD = %11111100 set only PoRTD pin 0 and 1 to outpuLs
X VAR BYTE d e c L a r e x a s a v a r i a b l e
turned PORTD.I ON & conpare io PoRTD.o

I.OOP:
FOR x = 1 TO 255 SIEP 2 set up foop foi x
PIIM PORTD. O, X, 3 vary Lhe duty cycLe
PAUSE 200 /X pauses longer for the dimer values
NEXT X en.f of Loop for x
GOIO LOOP reLurn and do i! again
END all progxans Fith an END statenent
With the preceding programs, we learned that we can control theON OFF staie anci
the brightness on an LED. Controlling the brighhess will become relevan! when we
are conrolljng seven segmenl displays because the LEDS in them dre tuned ON one
at a time and thc duty cycle has to be managed pfoperly 10 get an acceptable display