Help with LCD's

Ductapemaster · 2007-12-13 07:18

I had a 20x4 LCD (parallel) laying around and this afternoon I was messing with it. I got it to initialize and display whatever cursor I specify and I am able to send data to it and have it display it. However, I want to be able to send a string a data to it instead of sending it character by character. I messed around with lookup tables (just input the string in a table, each character separated by a comma) and it works, but thats a really dumb solution...

So basically I'm asking if there is a way to split a string up into individual characters so I can output one, then move to the next, output it, etc, etc.

Anyone have a solution?

Thanks in advance!

-Dan

David B · 2007-12-13 15:57

Here's a way to do this with fixed strings, using assembly.

What I've been doing is to declare a string so it ends with a zero, like this -

hello dw 'Hello World! ',0

To display the string, write its address to the W register, then call the write_string routine -

mov W, #hello
call @lcd_write_string

The write_string routine copies the contents of W to an address pointer, which it then steps along, displaying each individual character until it reaches a zero -

_lcd_write_string

bank48 bank_LCD
mov string, W

:loop

bank48 bank_LCD
mov W,string
mov M, #0
iread ; reads value from 11-bit code address in M, W
test W
jz @:end
call @lcd_write_data

bank48 bank_LCD
inc string
jmp @:loop

:end
retp

Does that help?

David

Ductapemaster · 2007-12-13 22:01

Heh, I'm an SX/B person (plan on learning more assembly during the Christmas holiday) but I will decipher it. It's pretty simple and I get the overall workings of it, I just need to understand what each individual instruction does.

Thanks a lot!

-Dan

Sparks-R-Fun · 2007-12-13 22:44

You can find an example of one possible way to process text strings in the RFID Reader example of the SX/B help file. Look at the LCD_OUT subroutine. The example uses a serial LCD but this should not present a significant problem for you since you already have the basic parallel LCD communication routines working. Just replace the SEROUT statement in the example with whatever you presently use to send a byte to your parallel LCD.

The example also uses a zero byte to terminate a text string. This is a common practice. If you place the text of the string in quotes SX/B includes the terminating zero byte for you automatically in the generated code.

- Sparks

Bean · 2007-12-29 13:41

Assuming you already have an LCD_Char subroutine, do this:

 
tempW       VAR WORD
temp        VAR BYTE
 
LCD_Char    SUB 1 ' Pass character to print
LCD_Str     SUB 2 ' Pass string to print
 
Program Start
 
Start:
  LCD_Str "Hello there"
  LCD_Str Message1
END
 
SUB LCD_Char
  ' What ever code you need here
ENDSUB
 
SUB LCD_Str
  tempW = __WPARAM12
  DO
    READINC tempW, temp
    IF temp = 0 THEN EXIT
    LCD_Char temp
  LOOP
ENDSUB
 
Message1:
  Data "This is a message", 0  ' Don't forget the zero at the end

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Help with LCD's

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