SUMMARY PIC16CXXX ideally suited interface directly keypad applic
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AN552
SUMMARY
PIC16CXXX ideally suited interface directly keypad application. Built pull-up resistors very current consumption during sleep make very good candidate battery powered remote operations applications. Appendix provides example code. Performance: Code Size Used words bytes
Implementing Wake-up Stroke
Stan D'Souza Microchip Technology Inc.
INTRODUCTION
Microchip's PIC16CXXX microcontroller family ideally suited directly interface keypad. high 4-bits PORTB (RB7:RB4) have internal pull-ups trigger "change state" interrupt. This interrupt, enabled, will wake microcontroller from SLEEP. most battery powered applications, microcontroller exercised when pressed (e.g., remote keyless entry system). life battery extended using PIC16CXXX microcontrollers. This done putting PIC16CXXX microcontroller into SLEEP mode most time wake-up only when pressed.
FIGURE
INTERFACE PIC16CXXX
4x1k LED1 LED2 LED3 LED4 4x100
PIC16CXXX
IMPLEMENTATION
Figure depicts application where four keys connected RB7:RB4. Internal pull-ups used maintain high level these inputs. this example, LEDs connected RB3:RB0. When pressed, LED1 turned when pressed, LED2 turned PIC16CXXX normally SLEEP mode with "change state" interrupt enabled. When pressed, goes triggers interrupt. Since PIC16CXXX SLEEP, first wakes starts executing code interrupt vector. Note that global interrupt enabled, program execution after interrupt interrupt vector, global interrupt enabled, program starts executing first line code right after SLEEP instruction. After waking de-bounce delay executed which checks port and, depending which hit, associated turned LEDs used purely demonstration purposes. remote keyless entry application, remote code would transmitted when appropriate hit. Figure depicts keypad interface PIC16CXXX microcontroller. When using PIC16CXXX keypad application, internal pull-ups RB7:RB4 enabled, eliminating need external pull-up resistors. series resistors used Electrostatic Discharge (ESD) protection, recommended keypad interface applications.
Matrix
FIGURE
KEYPAD INTERFACE PIC16CXXX
8x100
PIC16CXXX
1997 Microchip Technology Inc.
DS00552E-page
AN552
Please check Microchip latest version source code. Microchip's Worldwide Address: www.microchip.com; Bulletin Board Support: MCHIPBBS using CompuServe® (CompuServe membership required).
APPENDIX WAKUP.ASMPASM 01.40 Released WAKUP.ASM 1-16-1997 16:04:19 PAGE
OBJECT CODE VALUE
LINE SOURCE TEXT
00000002 00000007 00000010 00000001 00000001
0000 0000 2805 0004 0004 2808
0005 0005 2024 0006 0006 0000 0007 2806 0008 0008 0009 000A 000B 000C
180B 280D 128B 110B 0008
00001 00002 00003 00004 00005 00006 00007 00008 00009 00010 00011 00012 00013 00014 00015 00016 00017 00018 00019 00020 00021 00022 00023 00024 00025 00026 00027 00028 00029 00030 00001 00002 00142 00031 00032 00033 00034 00035 00036 00037 00038 00039 00040 00041 00042 00043 00044 00045 00046 00047 00048 00049 00050 00051
;This program demonstrates wake-up Keystroke feature ;the PIC16C71. Port pins configured inputs with ;internal pull resistors, also interrupt associated with ;change input wake chip from ;sleep. global interrupt enabled just before sleep, ;program will vector interrupt vector (0004). not, chip ;will continue execution just after next instruction following ;sleep. this example code, port initialized input ;push-buttons RB7. configured drive LEDs ;corresponding which pushbutton (LED when ;hit on). Sleep executed. When hit, ;processor wakes jumps interrupt vector. ;corresponding turned after released, ;whole process repeated. Program: WAKEUP.ASM Revision Date: 1-16-97 Compatibility with MPASMWIN 1.40 LIST P=16C71 RBPU temp OptionReg include "p16c71.inc" LIST ;P16C71.INC Standard Header File, Version 1.00 Microchip Technology LIST goto start goto ServiceInterrupt start call InitPortB ;initialize port loop sleep ;sleep till goto loop ServiceInterrupt btfsc INTCON,RBIF ;change int? goto ServiceWakup ;yes then service INTCON,T0IE ;clear TMR0 mask INTCON,T0IF ;clear flag return
DS00552E-page
1997 Microchip Technology Inc.
AN552
00052 00053 00054 00055 00056 000D 00057 000D 118B 00058 000E 0906 00059 000F 100B 00060 0010 2035 00061 0011 0906 00062 0012 39F0 00063 0013 0090 00064 0014 0E10 00065 0015 0086 00066 0016 2018 00067 0017 0009 00068 00069 00070 00071 00072 0018 00073 0018 2035 00074 0019 0906 00075 001A 100B 00076 001B 158B 00077 001C 39F0 00078 001D 1903 00079 001E 0008 00080 001F 0063 00081 0020 118B 00082 0021 0906 00083 0022 100B 00084 0023 2818 00085 00086 00087 00088 0024 00089 0024 1683 00090 0025 3003 00091 Message[302]: Register 0026 0088 00092 0027 3000 00093 0028 0085 00094 0029 30F0 00095 002A 0086 00096 002B 1381 00097 002C 1283 00098 002D 0186 00099 002E 0185 00100 002F 1405 00101 0030 118B 00102 0031 0806 00103 0032 100B 00104 0033 158B 00105 0034 0009 00106 00107 00108 00109 0035 00110 0035 1683 00111 0036 3007 00112 0037 0081 00113 0038 1283 00114 0039 0181 00115 003A 110B 00116 ;This routine checks which lights ;corresponding associated with RB0's when ;RB4's pressed. Finally waits till keys have ;been released before returning form service routine. ServiceWakup INTCON,RBIE ;clear mask comf PORTB,W ;read PORTB INTCON,RBIF ;clear flag call delay16 de-bounce 16mSecs comf PORTB,W ;read port again andlw B'11110000' ;mask outputs movwf temp ;save temp swapf temp,W ;switch high movwf PORTB ;send outputs. call KeyRelease ;check release retfie ;This sub-routine, waits till have been released order save power, chip sleep mode till ;all keys released. KeyRelease call delay16 debounce comf PORTB,W ;read PORTB INTCON,RBIF ;clear flag INTCON,RBIE ;enable mask andlw B'11110000' ;clear outputs btfsc STATUS,z ;key still pressed? return then return sleep ;else save power INTCON,RBIE wake clear mask comf PORTB,W INTCON,RBIF ;clear flag goto KeyRelease ;try again ;This sub-routine, initializes PortB. InitPortB STATUS,RP0 ;select bank1 movlw B'00000011' ;Port_A digital operand bank Ensure that bank bits correct. movwf ADCON1 movlw movwf PORTA ;set port outputs movlw B'11110000' ;RB0-RB3 outputs movwf PORTB ;RB4-RB7 inputs OptionReg,RBPU ;enable pull STATUS,RP0 ;select page clrf PORTB ;init port clrf PORTA ;make port PORTA,0 ;make first high INTCON,RBIE ;disable mask movf PORTB,W ;read port INTCON,RBIF ;clear flag INTCON,RBIE ;enable mask retfie ;enable global return ;delay16 waits approx 16.4mSecs using TMR0 interrupts ;fosc speed 4Mhz. delay16 STATUS,RP0 ;select Bank1 movlw B'00000111' ;fosc/256 TMR0 movwf OptionReg STATUS,RP0 ;select Bank0 clrf TMR0 INTCON,T0IF ;clear flag
1997 Microchip Technology Inc.
DS00552E-page
AN552
003B 003C 003C 003D 003E 003F 0040 00117 INTCON,T0IE 00118 CheckAgain 1D0B 00119 btfss INTCON,T0IF 283C 00120 goto CheckAgain 128B 00121 INTCON,T0IE 110B 00122 INTCON,T0IF 0008 00123 return 00124 00125 MEMORY USAGE ('X' Used, Unused) 168B ;enable mask ;timer overflowed? check again ;else clear mask ;clear flag
0000 X-XXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX 0040 -All other memory blocks unused. Program Memory Words Used: Program Memory Words Free:
Errors Warnings Messages
reported, reported,
suppressed suppressed
DS00552E-page
1997 Microchip Technology Inc.
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rights reserved. 1999 Microchip Technology Incorporated. Printed USA. 11/99
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1999 Microchip Technology Inc.
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