Page 82 - Making PIC Microcontroller Instruments and Controllers

7' COX'ROIL|XG THE OUIDUI AIID READII{G THE IIIPI'T

the keyboard rows and columns)
lilBi!iii?!i:gil4::l Read keyboard (Reading
(Continuect)
l,OW PORTE.2 ; LCD R/ll low (!vrite)
PAUSE 500 ; waiL for LCD !o starL uP

RIIADING VAR BYTE ; define the variabLes
A',PEA \ITR BYTE
BI'FFER 1IAR BYTE
; seL up port B pu1l ups
OPEION-REC, ? = O ; enabLe PORTB prrlL ups to nake B4-B7 high
IRISB = %11110000 ; nake B7 B4 inputs, B3 B0 outputs
BUFFER=%11111111 ; no key has been pressed fot disPLaY
; ser up the inilial LcD readinqs
tcDoun $FE, 1 ; clear the LCD
ICDOUT $FE, 9C0, 'ROW='.BIN4 {EUTFER & SoF)," CO!=",
BIN4 BUFFER >>4

looP:
PORTB -%OOOO1I1O ; set line BQ Lot so we can read xow 1
FoR ar,PEA = 1 to 4 ; only need !o look at 4 rows
LCDOtM $FE, g8O, BIIIS POBEB,' SCAIIVIEW Ez ; see bits scanned
rF (POREB & sFO)$FO fEEN one of lhe bias in 84
; to 87 changes we imediaLely
; have !o store Lhe value of PoRTB
BUFFER =PoRTB ; in a safe Place.
GOSUB SIIOI'IKEYPRESS
EIJSE
ENDTF
PAUSE 50 ; pause lets us see the scan but
; iL also neans hold a keY down
; for over 50 usecs Lo hawe at
; register. Pause be renowed
; after You hawe seen Lhe bits
; scaming on the LcD
FORIB= PORTB <<1 ; nove bits left one place for nert
; line 1ow
PORTB= PORTB + 1 ; put 1 back in LSBit, the righ! biL
NE'<T AI.PHA
GOTO t OOP

SHOWKEYPRESS
!
gco, \Ro!'r=Z,
r,cDott! saE, BrN4 {BUFFER & soF),-
\ cor,=z, BtN4 BUFFER >>4
RETURN
END