converting BCD question

KC8DKT

why does this not work

temp(1) = temp.NIB1(1)*10+temp.NIB0(1)

but this does

Temp = Temp(1)
Temp(1) = Temp.NIB1*10+Temp.NIB0

When converting BCD to DEC?· Not a big deal I know but its bugging me not knowing.

Jon Williams

You can't use variable modifiers with array elements -- but you can do this:

· temp(1) = (temp(1) >> 4 * 10) + (temp(1) & $0F)

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Jon Williams
Applications Engineer, Parallax

KC8DKT

debug myBytes.HIGHNIB(0)
debug myBytes.HIGHNIB(1)

I seen this in the help file and got the idea it would work with math, my bad, Thanks for the info and new formula.

Jon Williams

There is more than one way to skin this cat....· As it turns out, all of the RAM in the BASIC Stamp is considered an array and, usually, declaring an array is not the best thing to do.· Instead of:

time··· VAR···· Byte(3)

you can do this:

time··· VAR···· Byte
secs··· VAR···· time
mins··· VAR···· Byte
hrs···· VAR···· Byte

Using this strategy you can access secs as time(0), mins as time(1), and hrs as time(2).· But now you can do direct access as well.· So now you can use the BCD conversion:

· secs = (secs.NIB1 * 10) + secs.NIB0

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Jon Williams
Applications Engineer, Parallax

KC8DKT

Now that is sweat! Thanks...

Jon Williams

What I neglected to tell you is that you must declare your array elements in order with no breaks; that may be obvious but I think it's important to emphasize.

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Jon Williams
Applications Engineer, Parallax

KC8DKT

Yes it is.
After messing with this I rememberd reading about an array bug some where. Keep in mind that PBasic saves Large to small as well!

temp1 VAR Byte
temp2 var byte
temp3 var word

temp1(0) = 1
temp1(1) = 1
temp1(2) = 1
temp2 = 2
temp3 = 3

debug temp1(0) = 1
temp1(1) = 2
temp1(2) = 1 Word saved before byte. This would be the problem the bug could lead too.

No idea how this helps anyone but it was fun.

Bruce Bates

KC8DTK -

Quite regardless of whether there is an actual "bug" or not (which I rather doubt), your example leaves a bit of unfairness behind in its wake. Here's what I mean.

In total, your example works with FOUR bytes, TWO BYTES represented by temp1 and temp2 (one byte each) as well as TWO BYTES from temp3 (a WORD or two bytes), so it would make a good deal more sense to VIEW all FOUR bytes, after the fact, to examine their COMPLETE contents like this:

debug temp1(0), temp1(1), temp1(2), temp1(3)

or

debug temp1, temp2, temp3

Anything less than that hides some of the contents. Personally, in terms of proper and complete examination, I'd much rather see:

DEBUG IHEX? temp1, IHEX? temp2, IHEX4? temp3

but that's just the inherent bit-wacker in me talking

Regards,

Bruce Bates

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Jon Williams

I'm aware of no bugs in variable assignmet, KC,·and as you mention·-- by design -- the BASIC Stamp lays variables into memory largest to smallest:

Word
Byte
Nib
Bit

So your declaration:

temp1·· VAR··· ·Byte
temp2·· VAR··· ·Byte
temp3·· VAR··· ·Word

... would actually be stored in memory (as bytes) in this order:

temp3.LOWBYTE
temp3.HIGHBYTE
temp1
temp2

I guess another point I should have made absolutely clear is that implicit arrays only work with variables of the same type.

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Jon Williams
Applications Engineer, Parallax

KC8DKT

I said bug because I read somthing when I was working with the new BCD line. And after looking around I found it again.

A word of caution about arrays: If you're familiar with other BASICs and have used their arrays, you have probably run into the "subscript out of range" error. Subscript is another term for the index value. It is out-of-range when it exceeds the maximum value for the size of the array. For instance, in the example above, myBytes is a 10-cell array. Allowable index numbers are 0 through 9. If your program exceeds this range, PBASIC will not respond with an error message. Instead, it will access the next RAM location past the end of the array. If you are not careful about this, it can cause ALL SORTS OF BUGS.

Its in the new Help File for PBasic 2.2.5

Anyways, thanks for the new BCD line. Your new array(idx) fix worked out great for one small loop doing input & output converts too and from the RTC...

Jon Williams

To be clear, what you're referring to are programmer-induced errors, not bugs in the BASIC Stamp; let's just be very clear about that. And once one understands the operation of the BASIC Stamp memory, clever programmers can do a lot of neat tricks.

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Jon Williams
Applications Engineer, Parallax