Bits, Bytes Words and Arrays

[wellyboot]

ok... I've built an 8x8x8 LED cube using 18F452, I have encountered a problem with my array

each of the 512 leds as 1 bit assigned to it from leddata array

0 = bottom corner
511 = the top corner of the cube


leddata VAR BYTE[64]
litled VAR WORD

litled = 511
leddata.0(lilted) = 1

the above 2 lines lights up an led half way down the cube (I think it would correspond to 255)

but if I write this:

leddata.0(511) = 1

the correct LED lights up at the top corner of the cube

Any ideas?

[Ioannis]

You have an error in the variable litled.

leddata.0(lilted) = 1

It appears as lilted.

Ioannis

[wellyboot]

awww that was an autocorrect on here, not in my code

changed litled to 'lit' still no change,

I've changed my code now to address each led using X,Y,Z
and it is working ok


xl = 7
zl = 7
yl = 7
GOSUB ledon

ledon:
ledonbyte = xl + (yl*8)
ledtemp = leddata[ledonbyte]
ledtemp.0(zl) = 1
leddata[ledonbyte] = ledtemp
RETURN

[HenrikOlsson]

Hi,
I had a similar issue a couple of years (5) ago. Like you I found that indexing using a constant works but indexing using a variable doesn't (for bits beyond 255). And you, just like me back then, didn't bother to check the manual...

7.6.4 Accessing Arrays as Multiple Variable-Types
It is possible for a single array to be declared with multiple names and for each name to be assigned a different variable type. Note that offsets for BITs are limited to a maximum value of 255.

So, I Think Melanies post where she indicates that using a WORD as the pointer for indexing bits in a BYTE Array really isn't correct.

Here's my thread.

/Henrik.

[wellyboot]

Thanks Henik

solved that one

[richard]

The other option is a bit of asm code.
note the code would be slightly different for a pic18