Constants with BS2 and PBASIC 2.5

JimG

I want to be sure of what I am reading.· If I understand correctly you cannot define a CONSTANT that is a string, only a numeric value?· Is that any other method of pre-deining and naming a set of values short of setting up a variable for each one?



EX:



DoThisOrThat·· CON· "?f7"



Thanks,



Jim

Mike Green

The Stamp processors have very little string manipulation ability. They're basically treated as sequences of byte values. Only the various output statements can do anything useful with literal strings, so it makes little sense to have named string constants. What specifically are you trying to do?

JimG

Mike,

You again, huh? I am building a template to use to paint LCD's. It would be really nice if I could define all the various command strings with an English language Name. I can just put it all in as rem'ed text and pull out what I want...not as elegant but will work.

Ex:

MoveCursorRight CON "?i"



Jim

Mike Green

The other thing you can do is to have tiny subroutines for each command. If you have a serial LCD:

moveCursorRight:
  SEROUT lcdpin,baud,[noparse][[/noparse]"?i"]
  return

JimG

Mike,

What a great idea!! Doesn';t this consume lot of memory to store all the subs?

J

Mike Green

Sure, but program memory is relatively abundant on the Stamps.

allanlane5

Or you can declare your strings in "DATA" statements, then send them as "STR" variables.
Thus:

MyStr1 DATA "Hello", 0
MyStr2 DATA "Hello again", 0

SEROUT 16, 16864, [noparse][[/noparse]STR MyStr1, 13] ' Outputs "Hello" and CR, at 9600 baud, out programming port.
SEROUT 16, 16384, [noparse][[/noparse]STR MyStr2, 13] ' Outputs "Hello again" and CR

Your program is stored in EEPROM from 'top down', while DATA statements are stored in EEPROM from 'Bottom up' -- that is, address zero up.

JimG

Allan,

This might be a route to take too. Of course you have to be able to do simple math to use data staements and I am still on intermediate add and subtract.


Thanks,

Jim

Tracy Allen

The DATA statement doesn't take any math. It does however take a little subroutine to read and send the data:

MoveCursorRight DATA "?i",0  ' null terminated strings
Hello DATA "Hello", 0
Helloagain DATA "Hello again", 0

main:
DO
' ...
pointer = MoveCursorRight   ' reference by pointer
GOSUB LCDput
pointer=hello
GOSUB LCDPUT
' ...
LOOP

LCDput:
  DO
    READ pointer,char
    IF CHAR=0 THEN RETURN   ' null terminated DATA string
    SEROUT LCDpin, 16864, [noparse][[/noparse]char] 
    pointer=pointer+1
  LOOP

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Tracy Allen
www.emesystems.com

JimG

Maybe this is easier than I think it is. Let me chew on your sample for a little while. If I understand what you are saying, I can find the string on the EEPROM by name rather then having to figure out it's location, correct?

J

Tracy Allen

That's right, when you name some DATA, the name becomes the address of the data and you can use it in your program. For example,

MoveCursorRight CON "?i"
Debug DEC MoveCursorRight ' print the address
pointer = MoveCursorRight ' now pointer contains the address
READ pointer, char ' what's there, the first byte?
DEBUG TAB,HEX2 char '

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Tracy Allen
www.emesystems.com

JimG

I did a little more research in the book and think I understand.

Thanks,

Jim