Word Sized constant in Byte array

DynamoBen · 2009-05-17 04:11

I have several word sized constants that need to be place into a byte array which is subsequently sent via serial. For the life of me I can't figure out how to place both bytes into the array. I've tried bytemove, wordmove, constant.byte[noparse][[/noparse]x], but none of these seem to·work.

Can this be done? If so·how?

mctrivia · 2009-05-17 04:22

just use x>>8 to get the top half of the word.

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DynamoBen · 2009-05-17 04:35

Works perfect, thank you for the quick reply!

mctrivia · 2009-05-17 04:40

glad I could help.

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Need to upload large images or movies for use in the forum. you can do so at uploader.propmodule.com for free.

Beau Schwabe · 2009-05-17 04:50

DynamoBen,

Here is another "trick" that avoids using any shifting or math...

This demonstration uses the lights on the Propeller DEMO board.

CON
_clkmode          = xtal1 + pll16x                      
_xinfreq          = 5_000_000

PUB  MainProg
     L0 := %01100001_00110001_00011001_00001101
{               &#61600;        &#61600;        &#61600;        &#61600;
                &#9474;        &#9474;        &#9474;        &#9474;
           W1_highbyte   &#9474;   W0_highbyte   &#9474;                              
                         &#9474;                 &#9474;
                    W1_lowbyte        W0_lowbyte
}
     dira[noparse][[/noparse]16..23]~~
     repeat
       outa[noparse][[/noparse]16..23] := W0_lowbyte
       waitcnt(clkfreq*1+cnt)                           'Wait 1 second
       outa[noparse][[/noparse]16..23] := W0_highbyte
       waitcnt(clkfreq*1+cnt)                           'Wait 1 second
       outa[noparse][[/noparse]16..23] := W1_lowbyte
       waitcnt(clkfreq*1+cnt)                           'Wait 1 second
       outa[noparse][[/noparse]16..23] := W1_highbyte
       waitcnt(clkfreq*1+cnt)                           'Wait 1 second
DAT
L0            long
W0            word
W0_lowbyte    byte      0
W0_highbyte   byte      0
W1            word
W1_lowbyte    byte      0
W1_highbyte   byte      0

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

DynamoBen · 2009-05-17 05:31

Very interesting thanks Beau I may be able to use that.

Mike Huselton · 2009-05-17 08:53

This also provides an alternative scheme for coding data structures. I'll take any coding "tricks" that I can.

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JMH

Beau Schwabe · 2009-05-17 15:33

Just an additional note:
It isn't necessary to setup an entire variable array, you can just create one instance of a LONG defined in the DAT section like I have done...

DAT
L0            long
W0            word
W0_lowbyte    byte      0
W0_highbyte   byte      0
W1            word
W1_lowbyte    byte      0
W1_highbyte   byte      0

...·From there, if you need to determon what each byte is of a particular LONG, you can do something like ...

L0 := SomeOtherLongVariable
 
' W1_highbyte, W1_lowbyte, W0_highbyte, W0_lowbyte now hold the ordered bytes that are
' associated to SomeOtherLongVariable

... You can also use this method in reverse ...

W0_lowbyte  := %11001100
W0_highbyte := %10101010
W1_lowbyte  := %00110011
W1_highbyte := %01010101
 
' Causes L0 to equal... %01010101_00110011_10101010_11001100

· ... If you only wanted to affect the upper or lower WORD, then something like this would also work ...

W0 := %10111101_11100111
 
' This way, W0_highbyte equals %10111101 and W0_lowbyte equals 11100111

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Post Edited (Beau Schwabe (Parallax)) : 5/17/2009 3:46:58 PM GMT

MagIO2 · 2009-05-18 07:11

But that only works in DAT section, so if you want to write something for the ObjectExchange, please don't do it that way - or at least tell in the Header that this object can only be used as a singleton.

The way it should also work with variables is:

CON 
   word0 = $aaaa
   word1 = $1111
 
VAR
   myVar byte[noparse][[/noparse]10]
 
PUB main
 
   word[noparse][[/noparse] @myVar     ]:=word0
   word[noparse][[/noparse] @myVar + 2 ]:=word1

You only have to take care of the alignment of the byte array.

Word Sized constant in Byte array

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