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gautel
Joined: 04 Apr 2011
Posts: 3
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| help with writing "shift_right" in regular c langu |
 Posted: Mon Apr 04, 2011 8:01 am |
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Hello!
i have a problem with this function:
shift_right(RFbuffer+RFbuffer_index, 1, bitValue)
Can anyone please explain what it does? i understand that it should shift the bit's right, but not what happens when you write "RFbuffer+RFbuffer_index" as the variable.
I am currently working on a RFID reader using the CCS code for EM4095. And my problem is that i don't have very much experience using the CCS compiler, so i'm trying to write the code in knudsen C compiler.
I would be very grateful if someone could help me! 
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gautel
Joined: 04 Apr 2011
Posts: 3
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| Posted: Mon Apr 04, 2011 8:05 am |
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i should add that "RFbuffer" is an array, and "RFbuffer_index" is an integer!
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Ttelmah
Joined: 11 Mar 2010
Posts: 19553
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| Posted: Mon Apr 04, 2011 9:10 am |
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It shifts right the single byte at character location 'RFbuffer_index', in the array 'Rbuffer', shifting _in_ the value 'bitValue' to the vacated space, and returns the bit shifted out the bottom.
Since RFBuffer is int8, it'd be roughly equated in ANSI C by:
| Code: |
int8 shift_right(int8 *locn, int8 count, int8 val){
int8 rval=0
if (locn[count] & 1)
rval=1; //value to return
locn[count]/=2; //use division, since in C no guarantee that >>
//does not wrap.
if (val)
locn[count]|=128;
return rval;
}
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Best Wishes |
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gautel
Joined: 04 Apr 2011
Posts: 3
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| Posted: Mon Apr 04, 2011 9:29 am |
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Thank you very much for the help! 
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