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karlosguay
Joined: 12 Jun 2013
Posts: 20
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| Problem to convert array of bytes to array of bits |
 Posted: Wed Sep 11, 2013 2:08 am |
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Buenos días:
Estoy intentando hacer un programa donde tengo 19 bytes en una cadena (int telemando1[19]) y los intento leer y meter en otra bit a bit (int1 telemandobits[152]). El objetivo es que si tengo en la primera cadena los valores 8,7,.... pasen a la segunda cadena con los valores binarios 0,0,0,0,1,0,0,0, 0,0,0,0,0,1,1,1, ...
El código que tengo es:
| Code: |
int telemando1[19];
int1 telemandobits[152];
int i,z;
for (i=0;i==151;i++) //Aqui inicializo la cadena
{
telemandobits[i]=0;
}
//Estos son los datos que quiero pasar a la otra cadena bit a bit
telemando1[18]=8;
telemando1[17]=7;
telemando1[16]=6;
telemando1[15]=5;
telemando1[14]=4;
telemando1[13]=12;
telemando1[12]=0;
telemando1[11]=1;
telemando1[10]=17;
telemando1[9]=255;
telemando1[8]=255;
telemando1[7]=255;
telemando1[6]=255;
telemando1[5]=255;
telemando1[4]=255;
telemando1[3]=255;
telemando1[2]=255;
telemando1[1]=0;
telemando1[0]=0;
//Aquí creo una cadena de bits con todos los datos
for (i=18;i==0;i--)
{ for (z=0;z==7;z++)
{
telemandobits[((i+1)*8)-(8-z)]=(int1) telemando1[i];
telemando1[i]>>=1; // x>>=y, is the same as x=x>>y
}
}
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Luego leo la cadena telemandobits[] y no tengo los valores 0 y 1 esperados. La verdad es que creo que tiene que ser una tontería que no veo, pero me estoy volviendo loco. 
Alguna sugerencia??
Gracias |
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alan
Joined: 12 Nov 2012
Posts: 357
Location: South Africa
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| Posted: Wed Sep 11, 2013 2:11 am |
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Format are as follow for for loop
| Code: | | for (i=0; i<= 151, i++) { |
Regards |
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karlosguay
Joined: 12 Jun 2013
Posts: 20
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| Posted: Wed Sep 11, 2013 2:16 am |
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| Sorry Alan, I don´t understand |
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karlosguay
Joined: 12 Jun 2013
Posts: 20
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| Posted: Wed Sep 11, 2013 2:33 am |
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In English better
I need pass bytes in array "int telemando1[19]" to another array "int1 telemandobits[152]" bit to bit. If in the first array bytes are 8,7,6, ... I need in the second array 0,0,0,0,1,0,0,0, 0,0,0,0,0,1,1,1, 0,0,0,0,0,1,1,0, ....
| Code: | int telemando1[19];
int1 telemandobits[152];
int i,z;
for (i=0;i==151;i++) //Aqui inicializo la cadena
{
telemandobits[i]=0;
}
//Estos son los datos que quiero pasar a la otra cadena bit a bit
telemando1[18]=8;
telemando1[17]=7;
telemando1[16]=6;
telemando1[15]=5;
telemando1[14]=4;
telemando1[13]=12;
telemando1[12]=0;
telemando1[11]=1;
telemando1[10]=17;
telemando1[9]=255;
telemando1[8]=255;
telemando1[7]=255;
telemando1[6]=255;
telemando1[5]=255;
telemando1[4]=255;
telemando1[3]=255;
telemando1[2]=255;
telemando1[1]=0;
telemando1[0]=0;
//Aquí creo una cadena de bits con todos los datos
for (i=18;i==0;i--)
{ for (z=0;z==7;z++)
{
telemandobits[((i+1)*8)-(8-z)]=(int1) telemando1[i];
telemando1[i]>>=1; // x>>=y, is the same as x=x>>y
}
} |
But in "telemandobits" there are no correct values.
Any idea??
Thanks |
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alan
Joined: 12 Nov 2012
Posts: 357
Location: South Africa
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| Posted: Wed Sep 11, 2013 2:40 am |
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Yes your "for loop" never executes.
It set i = 0, then test if i == 152, and because it is not equal to 152 it exits the loop.
You have to test for i <= 152 and while this evaluates to TRUE, the for loop will execute. Sorry I am bad at explaining anything, but hope this helps.
Regards |
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karlosguay
Joined: 12 Jun 2013
Posts: 20
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| Posted: Wed Sep 11, 2013 2:53 am |
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OK Alan, you are a good teacher. 
regards |
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karlosguay
Joined: 12 Jun 2013
Posts: 20
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| Posted: Wed Sep 11, 2013 3:05 am |
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Now the code is
| Code: | for (i=0;i<=151;i++)
{
telemandobits[i]=0;
}
telemando1[18]=8;
telemando1[17]=7;
telemando1[16]=6;
telemando1[15]=5;
telemando1[14]=4;
telemando1[13]=12;
telemando1[12]=0;
telemando1[11]=1;
telemando1[10]=17;
telemando1[9]=255;
telemando1[8]=255;
telemando1[7]=255;
telemando1[6]=255;
telemando1[5]=255;
telemando1[4]=255;
telemando1[3]=255;
telemando1[2]=255;
telemando1[1]=0;
telemando1[0]=0;
//Aquí creo una cadena de bits con todos los datos
for (i=0;i<=18;i++)
{ for (z=0;z<=7;z++)
{
telemandobits[((i+1)*8)-(8-z)]=(int1) telemando1[i];
telemando1[i]>>=1; // x>>=y, is the same as x=x>>y
}
}
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But in "telemandobits" array i have 1,0,1,0,1,0,1,0,1,0,... |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19520
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| Posted: Wed Sep 11, 2013 3:34 am |
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>>=1, multiplies the value by 2. To get the next bit into the low bit you need <<=1. Explicitly test the low bit (=telemando1[i] & 1;). No cast needed.
However this is all basically not needed. You can create a union between the bits and the bytes, and the bits will all be there, with no copying needed. Instantaneous, versus a lot of code....
| Code: |
union {
int telemando1[19];
int1 telemandobits[152];
} val;
val.telemando1[18]=8;
val.telemando1[17]=7;
val.telemando1[16]=6;
val.telemando1[15]=5;
val.telemando1[14]=4;
val.telemando1[13]=12;
val.telemando1[12]=0;
val.telemando1[11]=1;
val.telemando1[10]=17;
val.telemando1[9]=255;
val.telemando1[8]=255;
val.telemando1[7]=255;
val.telemando1[6]=255;
val.telemando1[5]=255;
val.telemando1[4]=255;
val.telemando1[3]=255;
val.telemando1[2]=255;
val.telemando1[1]=0;
val.telemando1[0]=0;
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Then val.telemandobits[0] to [152], will contain the bits.
Best Wishes |
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karlosguay
Joined: 12 Jun 2013
Posts: 20
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| Posted: Wed Sep 11, 2013 3:47 am |
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Many thanks.
Never used "union", i go to use it. |
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alan
Joined: 12 Nov 2012
Posts: 357
Location: South Africa
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| Posted: Wed Sep 11, 2013 3:48 am |
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Hi Tthelmah, haven't you got it mixed. shift right >> divide and shift left << multiplies.
Regards
Alan |
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karlosguay
Joined: 12 Jun 2013
Posts: 20
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| Posted: Wed Sep 11, 2013 4:15 am |
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Using "union" runs ok.
then the code is better.
| Code: | union {
int telemando1[19];
int1 telemandobits[152];
} val;
// for (i=0;i<=151;i++)
// {
// telemandobits[i]=0;
// }
val.telemando1[18]=8;
val.telemando1[17]=7;
val.telemando1[16]=6;
val.telemando1[15]=5;
val.telemando1[14]=4;
val.telemando1[13]=12;
val.telemando1[12]=0;
val.telemando1[11]=1;
val.telemando1[10]=17;
val.telemando1[9]=255;
val.telemando1[8]=255;
val.telemando1[7]=255;
val.telemando1[6]=255;
val.telemando1[5]=255;
val.telemando1[4]=255;
val.telemando1[3]=255;
val.telemando1[2]=255;
val.telemando1[1]=0;
val.telemando1[0]=0;
//Aquí creo una cadena de bits con todos los datos
// for (i=0;i<=18;i++)
// { for (z=0;z<=7;z++)
// {
// telemandobits[((i+1)*8)-(8-z)]=(int1) telemando1[i];
// telemando1[i]>>=1; // x>>=y, is the same as x=x>>y
// }
// }
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Many thanks to all |
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