Quick 4x4 keypad matrix question
hello, quick question about keypad matrices.
I aquired a 4x4 matrix keypad for free and was trying to understand its operation in PBP. I started by using Bruce Reynolds code at: http://www.rentron.com/serkey16.htm.
All i am doing is waiting for a key to be pressed, then output the pressed key using HSEROUT on a PIC16F877@20Mhz.
I am using the schematic from rentron.
** The only change on my breadboard are resistors R1-R4 are 1k, not 270. **
The program kinda of works....sometimes when a button is pressed, the number sent via HSEROUT is actually the number below it.
i.e. Say the number "3" is pressed...most of the time the number "3" is displayed...but sometimes the number displayed will be "6", which is the button just below the "3" on the keypad.
Here is my slightly modified code...
Any help would be greatly appreciated. I have a strong feeling it is something simple. Thanks in advance.Code:'************************************************************ '* Name : serkey16.bas * '* Author : Reynolds Electronics * '* Date : 07/12/2001 * '* Version : 1.0 * '* Notes : PicBasic Pro program for 16-key serial keypad * '************************************************************ DEFINE OSC 20 '// Define Oscillator @ (X)mHz include "ansi.inc" Include "modedefs.bas" '--------------------------------------------------------------------- '---------- Define LCD Options --------------------------------------- '--------------------------------------------------------------------- Define LCD_DREG PORTD '// Define the data port define LCD_DBIT 0 '// Select port bit [0-lower or 4-upper] define LCD_RSREG PORTC '// Select RS port DEFINE LCD_RSBIT 4 '// Set RS bit (port number) define LCD_EREG PORTC '// Set E port define LCD_EBIT 5 '// Set E bit define LCD_BITS 4 '// 4 or 8 bit LCD '--------------------------------------------------------------------- '----------[Define HSEROUT Options]----------------------------------- '--------------------------------------------------------------------- DEFINE HSER_TXSTA 20h DEFINE HSER_RCSTA 90h DEFINE HSER_BAUD 9600 'DEFINE HSER_SPBRG 25 '// commented out to get 9600baud working col VAR BYTE '// Keypad column row VAR BYTE '// Keypad row key VAR BYTE '// Key value 'baud VAR PORTA.0 '// Baud select pin baud VAR bit '// let baud be compiler controlled trx_pin VAR PORTA.0 '// serial output pin mode var word 'CMCON = 7 '// PortA = digital I/O 'VRCON = 0 '// Voltage reference disabled 'TRISA = %00000001 '// PortA.0 = baud select pin OPTION_REG.7 = 0 '// Enable PORTB pull-ups mode = 16780 baud = 1 '// set initial baud rate. for testing pause 300 '// let LCD initialize @ ClearScr '// clear screen @ CurHome '// return cursor to home startup: lcdout $FE,1 lcdout "-Serial Keypad-" hserout ["------------------------------",10,13] hserout ["-----[Serial Keypad Demo]-----",10,13] hserout ["------------------------------",10,13,13,13,13] loop: GOSUB getkey 'Get key from keypad send: IF baud = 1 THEN fast'If baud = 1 then N9600,else N2400 hserout [10,13,dec key,10,13] 'SEROUT2 trx_pin,N2400,[key]'Send key value out PortA.1 GOTO loop fast: hserout [dec key,10,13] 'SEROUT serpin,N9600,[key] GOTO loop 'Do it forever getkey: PAUSE 100 'Debounce key-input getkeyu:' Wait for all keys up PORTB = 0 ' All output-pins low TRISB = $f0 ' Bottom 4-pins out, top 4-pins in IF ((PORTB >> 4) != $f) THEN getkeyu'If keys down, loop PAUSE 50 ' Debounce key-input getkeyp:' Wait for keypress FOR row = 0 TO 3 ' 4 rows in keypad PORTB = 0 ' All output-pins low TRISB = (DCD row) ^ $ff ' Set one row pin to output col = PORTB >> 4 ' Read columns IF col != $f THEN gotkey' If any keydown, exit NEXT row GOTO getkeyp ' No keys down, go look again gotkey: ' Change row and column to key number 1 - 16 key = (row * 4) + (NCD (col ^ $f)) 'NOTE: for 12-key keypad, change to key = (row * 3) RETURN ' Subroutine over END
Sean
It looks modified for all get out to me. 
.
Originally Posted by triton99
Re: Quick 4x4 keypad matrix question
Bookmarks