I2CWRITE not writing anything on PIC18F45K80

[CuriousOne]

Found another bug/issue.

Here's simple code:

topline	var byte [16]  'top part of the screen array
botline var byte [16] 'bottom part of screen


arraywrite topline,["0123456789ABCDEF"]
arraywrite botline,["0123456789ABCDEF"]






FOR X=0 TO 30 step 2	'READ ARRAY INTO VARIABLE, ARRAY MEMBER CHAR=EEPROM OFFSET	
if X<=15  then
Y=(botline[x]-48)*8
Z=(botline[x+1]-48)*8 'READ  INTO VARIABLE AS TWINS
endif




FOR I=0 TO 7	'HELPER LOOP FOR CHARACTER READING
LCDOUT $FE,$80+c+i 'UPDATE Y POSITION
LCDOUT $FE,$80+x/2 'UPDATE X POSITION
READ Y+I,A 'READ EEPROM BYTES INTO VAR
READ Z+I,B


if topline[x]=32 or botline[x]=32 then a=0
if topline[x+1]=32 or botline[x+1]=32 then b=0 'blanker


if atrib=1 and X<16 then
a=A^%11111111
b=b^%11111111
endif


if a=$FE then a=0
if b=$fe then b=0




LCDOUT a
LCDOUT b 'WRITE TO SCREEN
NEXT I
NEXT X

It should display 0123456789ABCDEF on LCD screen. It does, but there's an issue.

If reading text from 1st declared array (topline), then it is displayed correctly. However, if reading from 2nd declared array (botline), one of characters will be randomly missing in displayed text. This is not issue of my code, because if I do not declare "topline" array, then "botline" reading works fine.

So what this means, 18F45K80 can't handle two 16 byte arrays at same time?

[tumbleweed]

Your arrays are declared as 'var byte[16]'

topline var byte [16]
botline var byte [16]

That means a valid array index is from 0-15

This code here will fail when x=15

if X<=15  then
Y=(botline[x]-48)*8
Z=(botline[x+1]-48)*8 'READ  INTO VARIABLE AS TWINS

Z will try and access botline[x+1] = botline[16], which is invalid

[CuriousOne]

X is being incremented in steps of 2, so it will never be 15.
I even modified code so that X will never exceed 14 - issue is still here, but there is some logic in it.

I tried to add code in loop and look at output.
it changes in the following way based on loop step:

012345 789ABCDEF
0123456789 BCDEF
012345678 ABCDEF
01234567 9ABCDE

[CuriousOne]

Did a test with various size of arrays.
If both arrays do not exceed 24 bytes total, then everything is fine. As they exceed 24 bytes, issues start to appear.

[tumbleweed]

Fair enough, but what about this when x >= 16

if topline[x]=32 or botline[x]=32 then a=0
if topline[x+1]=32 or botline[x+1]=32 then b=0 'blanker

[CuriousOne]

I don't see any relation
I modified code and X now changes from 0 to 14 - still same issue.

[tumbleweed]

You've been using x, y, and z to get values to set a and b.
You've been shoving invalid data out to the lcd and wondering why the display is wrong.

It's probably still wrong.

[CuriousOne]

LOL.
I'm trying to explain that if I add one extra array definition, another array gets screwed. How this is related to LCD?
I just wrote another code, which simply reads values of array and writes data on 1602LCD.
Issue still exists - data in array gets damaged, if total array length exceeds 24 bytes.