Inconsistent output on a 4x4 matrix keypad

[markcadcam]

Hi Peterdeco1,

I appreciate the feedback but unfortunately I have made a circuit board for this design which is already installed in a piece of equipment. If I cannot get this to work I’ll give your idea a try.

Thanks,
Mark

[mister_e]

Alternative...

include "C:\PBP_PROG\INCLUDE_ROUTINES\KeyPad.bas"

define OSC 20
DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_SPBRG 129 ' 9600 Baud @ 0.16%
DEFINE HSER_CLROERR 1 ' Clear overflow automatically

DEFINE KEYPAD_ROW        4        ' 4 ROW keypad       
DEFINE KEYPAD_ROW_PORT   PORTB    ' ROW port = PORTB
DEFINE KEYPAD_ROW_BIT    0        ' ROW0 = PORTB.4
DEFINE KEYPAD_COL        4        ' 4 COL keypad
DEFINE KEYPAD_COL_PORT   PORTB    ' COL port = PORTB
DEFINE KEYPAD_COL_BIT    4        ' COL0 = PORTB.0
DEFINE KEYPAD_DEBOUNCEMS 200      ' debounce delay = 200 mSec
DEFINE KEYPAD_AUTOREPEAT 1        ' use auto-repeat feature 

INTCON2.7=0
kKey    var byte

Start:
    @ READKEYPAD _kKey
    hserout ["Key=",dec kkey,13,10]
    goto start

Just modify the include to suite your requirement
kEYpAD.BAS... AVAILABLE BELLOW
http://www.picbasic.co.uk/forum/showthread.php?t=3250

and IN YOUR serout LINE...

SEROUT serpin,N2400,[#key,#B0]'Send key value out PortA.1

AND now that some know you experiment a Write/Read/Modify behaviour... use your existing code but modify it like

getkeyu:' Wait for all keys up
    LATB = 0 ' All output-pins low
    TRISB = $f0 ' Bottom 4-pins out, top 4-pins in
@   nop
    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
        LATB = 0 ' All output-pins low
        TRISB = (DCD row) ^ $ff ' Set one row pin to output
@       nop
        col = PORTB >> 4 ' Read columns
        IF col != $f THEN gotkey' If any keydown, exit
        NEXT row
    GOTO getkeyp ' No keys down, go look again

What happen now ?

[markcadcam]

I'll give it a try.

Thanks,
Mark

[Ioannis]

If you still have problem after Steve's suggestions, please check the circuits. Better send the circuit here to see how you connected the buttons to the PIC. I suspect noise from some lines.

Ioannis

[mister_e]

FYI, using his code, i had similar problem as markcadam, so i decide to use my 'easy to use' INCLUDE with the same PIC and crystal... confirm that my hardware was good (EasyPIC4 + Keypad 4X4 adapter). Worked with internal pull-up AND external (of course).

Then i worked around his code. Use LATB intead of PORTB to write to the port for safety sake. On a whole port write, it doesn't really matter.. but when you write to few bit .. it may cause some problem. In this case leaving PORTB AS IS, will work anyways.

Writing to PORT before TRIS is also for safety sake even if some don't believe it But if you leave it like this... it still working.. but sometimes you have some screwed values

BUT the real magic is in the @ nop. remove those lines and the readings are screwed up.. or intermittent. just by this famous PIC18Xxxxx feature called 'Read/Modify/write' behaviour.

18Fs are much noise sensitive.. so i would avoid to use internal weak-pull-ups... IMHO.. you know i hate those anyways

[mister_e]

mmm, just double/triple/quad check the whole thing...
it appear that the TRIS work better if before the PORT/LATB line ....DOH!

BUT if you want to use the 'Microchip says' approach (write to PORT before TRIS), replace @ nop by @ GOTO $+2

That way... it works ... a treat

M.F.Sorry!

[Ioannis]

Hi Steve. Doesn't @ GOTO $+2 being equal to jump to next instruction? Also the same as NOP. So whats the difference?

Ioannis