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Bit shifting

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Prefekt

Joined: 21 Oct 2010
Posts: 85

Bit shifting

Posted: Fri Oct 05, 2012 2:41 pm

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Hello,

I'm confused...

I have a char array

Code:

a[0] = '0';
a[1] = '1';

now I would like to set the output with the a[1] value...

for example:

Code:

a[1] = 3;
out = 00000100;

or

Code:

a[1] = 7;
out = 01000000;

I try:

Code:

out =1;
out = out << a[1];
output_d(out);

not working..

anybody an idea?

thanks

PCM programmer

Joined: 06 Sep 2003
Posts: 21708

Posted: Fri Oct 05, 2012 4:54 pm

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You want to convert a bit number to a bitmask. Use a lookup table.
With the following table placed above main(), you can now put in code
in main() to get the bitmask. Use a number from 0 to 7 as the index
to get the bitmask for bit number 0 to 7. For bit 0, you will get 0x01,
and for bit 7 you will get 0x80, etc.

Code:

int8 const bitmask_table[] = {0x01,0x02,0x04,0x08,0x10,0x20,0x40,0x80};

To use your incoming numbers as index values for this table, you will
need to convert them from ASCII characters to binary digits in the range
from 0 to 7.

This post may have some hints.
http://www.ccsinfo.com/forum/viewtopic.php?t=48590&start=3

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