Lpc2000

i m final year student of electronics engg

 i  m trying to interface 16x2 lcd display with lpc
2106 

io ports are connected as follows

D0-P0.21.........D7-P0.28
lcd enable-p0.29    RS-p0.30
R/W is grounded

i have sucessfully implimented clear disply command
but i m not able to write data

is it the problem of driving capcity or voltage levels

please give solution.......
 
 

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I have driven a 4x20 display off an lpc2106 without any problem. 

You only need 7 GPIO lines for these: DB4-DB7, E, data/cmd, and r/w. Because you can drive these devices in 4 bit mode - That way you use less micro lines and PCB real estate.

Another useful trick is sharing the 4 data lines with a keypad driver - possible because these line are usually 
in high impedance. 

The only interfacing hardware I used between the LCD module and the 2106 were 4 pull up resistors on the data lines - but this was nencessary for the keypad circuit not the LCD. 

You've probably got a code bug.

Have fun!

Owen Mooney


 
Message: 19        
   Date: Wed, 13 Apr 2005 08:48:37 +0100 (BST)

   From: rohan patil <iamrohanpatil@...>
Subject: 
I O Port driving capacity
  i m final year student of electronics engg

 i  m trying to interface 16x2 lcd display with lpc
2106 

io ports are connected as follows

D0-P0.21.........D7-P0.28
lcd enable-p0.29    RS-p0.30
R/W is grounded

i have sucessfully implimented clear disply command
but i m not able to write data

is it the problem of driving capcity or voltage levels

please give solution.......

A logical (EE's need this quality) analysis of your problem arrives at 
these facts:

1) D0-D7 are working (enough) as an instruction has been processed
2) lcd enable must be working as an instruction has been processed (so 
you say)
3) RS is certainly low to interpret an instruction

Conclusion-
1) RS could be stuck low or you are not allowing enough setup time 
before enable
    Data setup time =>195ns
    RS setup time => 60ns  (you can't just combine this with the enable 
signal)

2) You are not following the proper initialisation steps which are (for 
8-bit)
    1. wait 15ms after VCC rises to 4.5V
    2. Write instruction 30h      ;8-bit interface
    3. wait more than 4.1ms
    4. Write instruction 30h      ;mmmm, better make sure it's set to 8-bit
    5. wait more than 100us
    6. Write instruction 30h      ;do it again! (should be right now)
       + wait 40us                ; R/W tied low - assume max timeout
    7. Write instruction 38h      ;8-bit interface, 2 lines
       + wait 40us
    8. Write instruction 0Fh      ;display on, cursor and blinking (for 
test)
       + wait 40us
    9. Write instruction 01h      ;clear display
       + wait up to 5ms           ;!!! this is as fast as it will go
    10. Write instruction 06h     ;standard entry mode
       + wait 40us
    11. Write data + wait 40us etc


*Peter*

rohan patil wrote:

>  i m final year student of electronics engg
>
> i  m trying to interface 16x2 lcd display with lpc
>2106 
>
>io ports are connected as follows
>
>D0-P0.21.........D7-P0.28
>lcd enable-p0.29    RS-p0.30
>R/W is grounded
>
>i have sucessfully implimented clear disply command
>but i m not able to write data
>
>is it the problem of driving capcity or voltage levels
>
>please give solution.......
>

Oh, on a final note, note the subject of your query. You assume it is a 
port drive problem rather than what you should be stating; that you are 
having a problem writing to the lcd "but i m not able to write data". 
Correctly state what your problem IS rather than what you think the 
problem might be "is it the problem of driving capcity or voltage levels".

Stating the actual problem will help you not only in EE but also in your 
personal life etc etc :)

BTW, logic high on an LCD is at least 2.2V so 3.3V is no problem.

*Peter*


rohan patil wrote:

>  i m final year student of electronics engg
>
> i  m trying to interface 16x2 lcd display with lpc
>2106 
>
>io ports are connected as follows
>
>D0-P0.21.........D7-P0.28
>lcd enable-p0.29    RS-p0.30
>R/W is grounded
>
>i have sucessfully implimented clear disply command
>but i m not able to write data
>
>is it the problem of driving capcity or voltage levels
>
>please give solution.......
>
>