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how to define a pointer to a large const array

 
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electrogen



Joined: 24 Feb 2009
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how to define a pointer to a large const array
PostPosted: Tue Mar 23, 2010 10:29 am     Reply with quote
I was interfacing an LCD with 18F458. I've a large array of char which has 1538 byte elements to store large fonts.

Does the compiler support pointer to an array of size more than 256 bytes??
if so, how can I define this pointer?
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PostPosted: Tue Mar 23, 2010 12:58 pm     Reply with quote
Look at the TEXT[][] arrays and the glcd_text57() function in this file:
Quote:

c:\program files\picc\drivers\glcd.c

Notice how the TEXT data is broken up into two arrays. That's done
because of the 'const' array limit of 256 bytes for the PCM compiler.
The PCH compiler (18F) doesn't have this size restriction. But the
glcd.c file is done this way so it will work with both compilers.

For example, with the PCH compiler, you can edit the TEXT and TEXT2
arrays, and combine them into one array. Then you don't have to do
a test on the input char value, to see which array to use. You could just
have one line to copy the 'const' font data to a RAM array. Example:
Code:

memcpy(pixelData, TEXT[textptr[i]-' '], 5);
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