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Smart LCD usage

 
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Neckruin



Joined: 17 Jan 2006
Posts: 66

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Smart LCD usage
PostPosted: Thu Oct 12, 2006 1:50 am     Reply with quote
Hello all,
I'd like to ask for some suggestions about LCD usage. I'm developing a project in wich I have to use an LCD to show a big ammount of different messages, menus, scroll then, select options, etc. The problem is that this is the first ever time I use an LCD.
I'm using PIC16F877 and 20x4 LCD from Powertip. I have already found PCM's flex_lcd420.c and tried a bit, showing some messages and similar.
Now I'd like to ask you for suggestions on some topics that I have found while thinking about the problem. Let's go!

1st: I have to show a big ammount if different messages, so they can not be allocated in RAM, they must be constants on program memory. Is this the best option? In case it is... how can I force them to be allocated in PM?

2nd: Some of the messages I have to show are composed by a constant part and a variable one. For example: "Status = X", where X can be one of several strings like "OK" or "BUSY". How can I combine fixed and variable strings to show them in the best way to save as much memory as possible (16F877 has very few mmory)?

3rd: The menu. I have to show a menu and scroll it. Any suggestion about how to move the menu? I also have to know where the focus is, I mean, which option from the menu the user has selected and feedback him in some way (by showing that line different). How can I do that?

Well, at the moment I think this is all. I'm looking forward to hear your suggestions. If I find any extra trouble I'll post it here as well.

THANK YOU VERY MUCH IN ADVANCE!!!

Yours,

Juanma Very Happy
Mattr0



Joined: 27 Mar 2005
Posts: 30

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PostPosted: Fri Oct 13, 2006 10:17 am     Reply with quote
Juanma,

I have used many LCDD screens in my designs. I agree with you that you do not want to store the messages in ram. You want to define them as a constant like this.

Code:
const char  menu1[]="Option1";

this will store the string Option1 in PM memory. to get it to the LCD screen use the printf command

Code:
printf(LCD_PUTC, "%s",menu1);

this will print Option1 on the LCD.

also look at the LCD420.C it is included with the compiler. The printf command would be compatible with this driver.

The printf command is also how you would create varible strings
for example

Code:

int x = 57;
char good[] = "ok";
printf(LCD_PUTC, "%s %u %s",menu1,x,good);


this will print

Option1 57 ok

on the LCD screen

you should look at the printf command for more options

asfar as the menu goes make a state machine out of it. It will be the easiest way to handle it.

good luck
Neckruin



Joined: 17 Jan 2006
Posts: 66

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PostPosted: Sat Oct 14, 2006 4:05 am     Reply with quote
Thank you very much Mattr0 Very Happy

Your comments will be really useful for me.

Thanks a lot again.
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