please dont rip this site

PIC Microcontroler based Keyboards

4x4 Keypad with 1 A/D pin:

Dennis Crawley says:

The diagram below shows how this can be done, by connecting the row/column lines of the keypad to resistors so that each key (the X's in the diagram below) results in a different resistance value. This resistance is connected, along with a load resistor (the 22K shown below), in a voltage divider between Vcc and ground; each key gives a different voltage, thus a different A/D reading.

Observations:

  1. It requires 1% resistors, but it could be tested with normal 20% tolerance.
  2. It's very stable with voltage fluctuations.
  3. Since keyboards come with some resistance 80-100 ohms, and they tend to grow, the soft need some calibration as well as keyboard change over the time,...

Basically, the program transmit each key pressed to a terminal, so the programmer can see the key real value. Once he/she *calibrate* the range the pic is ready to use.

;**********************************************
        LIST    P=PIC16F873,F=INHX8M,R=DEC
        #INCLUDE P16F873.INC
        __CONFIG _HS_OSC&_WDT_OFF&_CP_OFF&_PWRTE_ON&_BODEN_ON&_LVP_OFF
        ERRORLEVEL 1,-302
;**********************************************
;Fosc 16Mhz
;First commented on PicList by Dave Dilatush
;Sat, 9 Feb 2002 20:43:39 GMT                                   
;Re: [PIC]: CHALLENGE: 4x4 keyboard and LCD with 1 port = 8 bits
;
;  X-------X-------X-------X----------+--Vcc      
;  |       |       |       |          |           
;  |       |       |       |          |           
;  X-------X-------X-------X---4.7K---+           
;  |       |       |       |          |           
;  |       |       |       |          |           
;  X-------X-------X-------X---10K----+           
;  |       |       |       |          |           
;  |       |       |       |          |           
;  X-------X-------X-------X---15K----+           
;  |       |       |       |                      
;  |     1.2K    2.4K    3.6K                     
;  |       |       |       |                      
;  +-------+-------+-------+--> To PIC A/D Input  
;                          |                      
;                         22K                     
;                          |                      
;                         GND                     
;
         CBLOCK 0X070            ;
BUFFER                           ;
LOOPS                            ;
LOOPS2                           ;
NIBBLE1                          ;
NIBBLE2                          ;
NIBBLE3                          ;
FILTER1                          ;
FILTER2                          ;
FILTER3                          ;
VECES                            ;
BUFFERKEY                        ;
        ENDC                     ;


        ORG     00               ;
        GOTO    INIT             ;
                                 ;
;Delay. @4Mhz-1ms.
RETARDO                          ;
        MOVWF   LOOPS            ;
TOP2    MOVLW   D'110'           ;
        MOVWF   LOOPS2           ;
TOP     NOP                      ;
        NOP                      ;
        NOP                      ;
        NOP                      ;
        NOP                      ;
        NOP                      ;
        DECFSZ  LOOPS2           ;
        GOTO    TOP              ;
        DECFSZ  LOOPS            ;
        GOTO    TOP2             ;
        RETURN                   ;

;ADC                                 
CONVER  BSF     ADCON0,GO        ;
CONSU   BTFSC   ADCON0,GO        ;
        GOTO    CONSU            ;
        RETURN                   ;
                                 
;Resistors and  Keys Resistances 
;may vary over the time 
;so we established ranges for
;each converted value with:
;addlw 255 - Hi                  
;addlw (Hi - Lo) + 1             
;for a good explanation go to:
;http://www.piclist.com/techref/microchip/rangechk.htm
;********************************;
PARSER                           ;
       CLRF   BUFFERKEY          ;Split de hexa into
       MOVLW  .3                 ;two nibbles. Test for
       XORWF  FILTER1,W          ;Hi nibble, If = 3
       BTFSS STATUS,Z            ;Test the low nibble
       GOTO   TWO                ;otherwise jump.
;3FC ---> real value got it from TOASCII routine                      
       MOVFW  FILTER2            ;
       ADDLW  255 - 0X0FE        ;
       ADDLW  (0X0FE - 0X0E8)+1  ;
       MOVLW  "1"                ;
       BTFSC STATUS,C            ;
       GOTO   SAVEKEY            ;
;3C4                       
       MOVFW  FILTER2            ;
       ADDLW  255 - 0X0C8        ;
       ADDLW  (0X0C8 - 0X0BF)+1  ;
       MOVLW  "2"                ;
       BTFSC STATUS,C            ;
       GOTO   SAVEKEY            ;
;39E                       
       MOVFW  FILTER2            ;
       ADDLW  255 - 0X0A2        ;
       ADDLW  (0X0A2 - 0X09A)+1  ;
       MOVLW  "3"                ;
       BTFSC  STATUS,C           ;
       GOTO   SAVEKEY            ;
;363                       
       MOVFW  FILTER2            ;
       ADDLW  255 - 0X067        ;
       ADDLW  (0X067 - 0X05E)+1  ;
       MOVLW  "S"                ;
       BTFSC STATUS,C            ;
       GOTO   SAVEKEY            ;
;345                       
       MOVFW  FILTER2            ;
       ADDLW  255 - 0X049        ;
       ADDLW  (0X049 - 0X041)+1  ;
       MOVLW  "4"                ;
       BTFSC STATUS,C            ;
       GOTO   SAVEKEY            ;
;31F                       
       MOVFW  FILTER2            ;
       ADDLW  255 - 0X023        ;
       ADDLW  (0X023 - 0X01B)+1  ;
       MOVLW  "5"                ;
       BTFSC STATUS,C            ;
       GOTO   SAVEKEY            ;
;305                       
       MOVFW  FILTER2            ;
       ADDLW  255 - 0X09         ;
       ADDLW  (0X009 - 0X01)+1   ;
       MOVLW  "6"                ;
       BTFSC STATUS,C            ;
       GOTO   SAVEKEY            ;

TWO                              ;Values with hi nibble
                                 ;equal to 2
;2DB 
       MOVFW  FILTER2            ;
       ADDLW  255 - 0X0E1        ;
       ADDLW  (0X0E1 - 0XD7)+1   ;
       MOVLW  "U"                ;U for UP
       BTFSC STATUS,C            ;
       GOTO   SAVEKEY            ;
;2BE
       MOVFW  FILTER2            ;
       ADDLW  255 - 0X0C2        ;
       ADDLW  (0X0C2 - 0XBA)+1   ;
       MOVLW  "7"                ;
       BTFSC STATUS,C            ;
       GOTO   SAVEKEY            ;
;2A3
       MOVFW  FILTER2            ;
       ADDLW  255 - 0X0A7        ;
       ADDLW  (0X0A7 - 0X9F)+1   ;
       MOVLW  "8"                ;
       BTFSC STATUS,C            ;
       GOTO   SAVEKEY            ;
;28E  
       MOVFW  FILTER2            ;
       ADDLW  255 - 0X092        ;
       ADDLW  (0X092 - 0X8A)+1   ;
       MOVLW  "9"                ;
       BTFSC STATUS,C            ;
       GOTO   SAVEKEY            ;
;271                       
       MOVFW  FILTER2            ;
       ADDLW  255 - 0X075        ;
       ADDLW  (0X075 - 0X06D)+1  ;
       MOVLW  "D"                ;D for Down
       BTFSC STATUS,C            ;
       GOTO   SAVEKEY            ;
;25C                       
       MOVFW  FILTER2            ;
       ADDLW  255 - 0X060        ;
       ADDLW  (0X060 - 0X058)+1  ;
       MOVLW  "P"                ;P for Program
       BTFSC STATUS,C            ;
       GOTO   SAVEKEY            ;
;248                       
       MOVFW  FILTER2            ;
       ADDLW  255 - 0X04C        ;
       ADDLW  (0X04C - 0X044)+1  ;
       MOVLW  "0"                ;
       BTFSC STATUS,C            ;
       GOTO   SAVEKEY            ;
;238                       
       MOVFW  FILTER2            ;
       ADDLW  255 - 0X03C        ;
       ADDLW  (0X03C - 0X34)+1   ;
       MOVLW  "B"                ;B for Backspace
       BTFSC STATUS,C            ;
       GOTO   SAVEKEY            ;
;222                       
       MOVFW  FILTER2            ;
       ADDLW  255 - 0X026        ;
       ADDLW  (0X026 - 0X1E)+1   ;
       MOVLW  "E"                ;E for Enter
       BTFSC STATUS,C            ;
       GOTO   SAVEKEY            ;

KEYBERROR2                       ;If some keys have      
       MOVLW  "#"                ;changed their values   
SAVEKEY                          ;the soft could handled 
       MOVWF  BUFFERKEY          ;the error              
       RETURN                    ;

;********************************;
TOASCII                          ;When is active,
        MOVF    FILTER1,W        ;this routine take the
        MOVWF   NIBBLE1          ;hex value and convert it
        MOVLW   30H              ;into three ascii values
        ADDWF   NIBBLE1          ;Basically check for
                                 ;ABCDEF1234567890
        MOVF    FILTER2,W        ;
        MOVWF   BUFFER           ;
        ANDLW   0FH              ;
        MOVWF   NIBBLE3          ;
        MOVLW   0AH              ;
        SUBWF   NIBBLE3,0        ;
        MOVLW   37H              ;
        BTFSS   STATUS,C         ;
        MOVLW   30H              ;
        ADDWF   NIBBLE3          ;
        SWAPF   BUFFER,0         ;
        ANDLW   0FH              ;
        MOVWF   NIBBLE2          ;
        MOVLW   0AH              ;
        SUBWF   NIBBLE2,0        ;
        MOVLW   37H              ;
        BTFSS   STATUS,C         ;
        MOVLW   30H              ;
        ADDWF   NIBBLE2          ;
        RETURN                   ;

;********************************;This routine add
FILTRO  CLRF    FILTER1          ;the converted value
        CLRF    FILTER2          ;into 3 registers.
        CLRF    FILTER3          ;256 times.
        CLRF    VECES            ;then divide by 256
REPEAT                           ;ignoring filter3.
        CALL    CONVER           ;ex:for 3FB 
        BSF     STATUS,RP0       ;filter1=0x003
        MOVF    ADRESL,W         ;filter2=0x0fb
        BCF     STATUS,RP0       ;
        ADDWF   FILTER3,1        ;
        BTFSS   STATUS,C         ;
        GOTO    FILT2            ;
        MOVLW   D'1'             ;
        ADDWF   FILTER2,1        ;
        BTFSS   STATUS,C         ;
        GOTO    FILT2            ;
        MOVLW   D'1'             ;
        ADDWF   FILTER1,1        ;
FILT2                            ;
        MOVF    ADRESH,W         ;
        ADDWF   FILTER2,1        ;
        BTFSC   STATUS,C         ;
        INCF    FILTER1          ;
        DECFSZ  VECES,1          ;
        GOTO    REPEAT           ;
                                 ;
        RETURN                   ;
                                 ;
                                 ;
                                 ;
TRASMI  BTFSS   PIR1,TXIF        ;
        GOTO    TRASMI           ;
        MOVWF   TXREG            ;
        NOP                      ;
TRASMI2 BTFSS   PIR1,TXIF        ;last bit is sent
        GOTO    TRASMI2          ;
        RETURN                   ;


;Main
INIT    BSF     STATUS,RP0       ;
        MOVLW   0FFH             ;
        MOVWF   TRISA            ;
        MOVWF   TRISB            ;
        MOVLW   B'11111111'      ;
        MOVWF   TRISC            ;
        MOVLW   B'00100110'      ;
        MOVWF   TXSTA            ;
        MOVLW   D'103'           ;16mhz crystal
        MOVWF   SPBRG            ;9600bps. If 4mhz is used,
        MOVLW   B'10000010'      ;change spbrg to (dec)25
        MOVWF   ADCON1           ;
        BCF     STATUS,RP0       ;
        MOVLW   B'10000001'      ;Fosc/32
        MOVWF   ADCON0           ;
        BSF     PIR1,TXIF        ;
        BCF     PIR1,RCIF        ;
        MOVLW   B'10010000'      ;
        MOVWF   RCSTA            ;
                                 ;
        MOVLW   "T"              ;welcom screen on pc
        CALL    TRASMI           ;
        MOVLW   "X"              ;
        CALL    TRASMI           ;
        MOVLW   " "              ;
        CALL    TRASMI           ;
        MOVLW   "O"              ;
        CALL    TRASMI           ;
        MOVLW   "K"              ;
        CALL    TRASMI           ;
        MOVLW   D'13'            ;
        CALL    TRASMI           ;
        MOVLW   D'10'            ;
        CALL    TRASMI           ;
                                 ;
                                 ;
CICLO                            ;
        CALL    FILTRO           ;check for pushed keys
        MOVLW   2                ;> than 2 in filter1
        SUBWF   FILTER1,W        ;
        BTFSS   STATUS,C         ;
        GOTO    CICLO            ;
                                 ;
        MOVLW   .83              ;almost 20 ms. 
        CALL    RETARDO          ;if 4mhz is used,
        CLRF    VECES            ;change to (dec)20
        CALL    FILTRO           ;
        MOVLW   2                ;
        SUBWF   FILTER1,W        ;
        BTFSS   STATUS,C         ;
        GOTO    CICLO            ;
;        CALL    TOASCII         ;un-comment this to see the 
        CALL    PARSER           ;key real value, so range can
RELEASE                          ;be adjusted
        CALL    FILTRO           ;check if key was released
        MOVLW   0X02             ;
        SUBWF   FILTER1,W        ;
        BC     RELEASE           ;
                                 ;
        MOVLW   ":"              ;
        CALL    TRASMI           ;
        MOVFW   BUFFERKEY        ;
        CALL    TRASMI           ;
;        MOVFW   NIBBLE1         ;un-comment to send keys
;        CALL    TRASMI          ;values to pc screen
;        MOVFW   NIBBLE2         ;
;        CALL    TRASMI          ;
;        MOVFW   NIBBLE3         ;
;        CALL    TRASMI          ;
        MOVLW   D'13'            ;
        CALL    TRASMI           ;
        MOVLW   D'10'            ;
        CALL    TRASMI           ;
                                 ;
        GOTO    CICLO            ;
                                 ;
        END

See also:

Comments:


file: /Techref/microchip/4x4key1ad7r.htm, 14KB, , updated: 2010/7/8 15:00, local time: 2024/12/22 22:54,
TOP NEW HELP FIND: 
3.16.212.203:LOG IN

 ©2024 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions?
Please DO link to this page! Digg it! / MAKE!

<A HREF="http://sxlist.com/Techref/microchip/4x4key1ad7r.htm"> PIC Microcontroler 4x4 Keypad with 1 A/D pin</A>

After you find an appropriate page, you are invited to your to this massmind site! (posts will be visible only to you before review) Just type a nice message (short messages are blocked as spam) in the box and press the Post button. (HTML welcomed, but not the <A tag: Instead, use the link box to link to another page. A tutorial is available Members can login to post directly, become page editors, and be credited for their posts.


Link? Put it here: 
if you want a response, please enter your email address: 
Attn spammers: All posts are reviewed before being made visible to anyone other than the poster.
Did you find what you needed?

 

Welcome to sxlist.com!


Site supported by
sales, advertizing,
& kind contributors
just like you!

Please don't rip/copy
(here's why

Copies of the site on CD
are available at minimal cost.
 

Welcome to sxlist.com!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  .