help with lcd/keypad interface

argmafia · 2006-03-01 15:16

need some help with schematic and code for the interface of an LCD and keypad (a 4x20 serial lcd and a 4x4 keypad)

Thank you

Jon Williams · 2006-03-01 15:21

This should help: http://www.parallax.com/dl/docs/cols/nv/vol4/col/nv97.pdf

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Jon Williams
Applications Engineer, Parallax

argmafia · 2006-03-01 17:17

what if we have a serial lcd, what then?

Jon Williams · 2006-03-01 17:26

No problem, just read the keyboard as shown in the article and send commands to your LCD on its own control pin (use the pin that was the LCD E line in the article). Easy.

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Jon Williams
Applications Engineer, Parallax

argmafia · 2006-03-01 19:41

are we going to use the same code??? or what needs to be changed???

argmafia · 2006-03-01 19:46

are we going to hook up all the wires(D0-D4 & data available) to the same LCD pin (pin E) in our serial LCD?

Jon Williams · 2006-03-01 20:07

Just remove the LCD and related code from that project; and now that P0 is free (was the E line), use that to send serial commands to your LCD.

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Jon Williams
Applications Engineer, Parallax

argmafia · 2006-03-01 21:46

But where do I connect the serial LCD and what code can I use?· Im sorry but I lack the programming ability and skills where maybe you could help me....

argmafia · 2006-03-01 21:53

you think maybe u can show me a schematic of how to hook it up and write the code where the lcd interfaces with the keypad???
thanks

argmafia · 2006-03-01 22:01

We are trying this code but we are unable to get the correct responses on the debug window. Are we doing something wrong??
Once I get the correct response, what commands do I need to send it to my LCD (initialization, baud rate... etc)?

' {$STAMP BS2}
' {$PBASIC 2.5}
' ========================================================================================

DIRL = %00001111 'p0 - p3 are outputs; p4-7 are inputs

x VAR Byte

DO
GOSUB scan 'go to subroutine scan
PAUSE 250 'pause for 250 ms
DEBUG x, CR 'output x to the screen
OUTA = 0 'set OUTA to be low
LOOP

scan: 'start of scan subroutine
DO
HIGH 0 'checking row one
IF (IN4 = 1) THEN one
IF (IN5 = 1) THEN two
IF (IN6 = 1) THEN three
IF (IN7 = 1) THEN A
LOW 0

HIGH 1 'checking row two
IF (IN4 = 1) THEN four
IF (IN5 = 1) THEN five
IF (IN6 = 1) THEN six
IF (IN7 = 1) THEN B
LOW 1

HIGH 2 'checking row three
IF (IN4 = 1) THEN seven
IF (IN5 = 1) THEN eight
IF (IN6 = 1) THEN nine
IF (IN7 = 1) THEN C
LOW 2

HIGH 3 'checking row four
IF (IN4 = 1) THEN asterisk
IF (IN5 = 1) THEN zero
IF (IN6 = 1) THEN pound
IF (IN7 = 1) THEN D
LOW 3
LOOP

one:
x = 49 'ascii for 1
RETURN

two:
x = 50 'ascii for 2
RETURN

three:
x = 51 'ascii for 3
RETURN

A:
x = 65 'ascii for A
RETURN

four:
x = 52 'ascii for 4
RETURN

five:
x = 53 'ascii for 5
RETURN

six:
x = 54 'ascii for 6
RETURN

B:
x = 66 'ascii for B
RETURN

seven:
x = 55 'ascii for 7
RETURN

eight:
x = 56 'ascii for 8
RETURN

nine:
x = 57 'ascii for 9
RETURN

C:
x = 67 'ascii for C
RETURN

asterisk:
x = 42 'ascii for *
RETURN

zero:
x = 48 'ascii for 0
RETURN

pound:
x = 35 'ascii for #
RETURN

x = 68 'ascii for D
RETURN

PJAllen · 2006-03-02 00:40

· In your Row Checking subroutines you're Branching to other subroutines (one, two, A, B, and so on) and terminating those same using "RETURN".
· Why?·
· RETURN only works if the Branch is the result of a GOSUB (not a GOTO).· I'm not sure where you want it to go to once you Detect a Key press and then you fetch the ASCII code (as you are.)· At present, you are IF...THEN GOTO'ing (when you don't write GOTO, it's implied that way.)· You can IF..THEN...GOSUB, but you have to write the GOSUB command.
· I suppose you could consider changing those RETURNs (e.g. GOTO Subr-Debug, or something.)

*****
Hope this Reply doesn't make me a Bad Guy.

Post Edited (PJ Allen) : 3/2/2006 12:48:18 AM GMT

help with lcd/keypad interface

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