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kda406
Joined: 17 Sep 2003
Posts: 97
Location: Atlanta, GA, USA
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| make8() not working |
 Posted: Thu Dec 09, 2010 2:02 pm |
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4.114, PIC18F8722
Make8() will not compile when a variable is used as the offset. Here is an example I created that will not compile: | Code: | void somefunction(void) {
int8 iData[4];
int32 lPortBit[] = { 0x00000010,0x000000020,0x00000040,0x00000080,0x00000100,
0x00000001,0x00000002,0x00000004,0x00000008 };
int8 iCnt,iOffset;
for(iCnt=0;iCnt<9;iCnt++) {
for(iOffset=0;iOffset<3;iOffset++) iData[iOffset] = make8(lPortBit[iCnt],iOffset);
fprintf(TERM,"%02X\n\r",iData[0]
}
} |
This would make iData[3] contain the MSB and iData[0] contain the LSB of the int32.
| Quote: | | *** Error 108 "AB12-IO.c" Line 121(39,46): Invalid parameters to built in function :: |
where line 121 is the line with make8() in it.
The CCS manual does not indicate if offset must be a constant. Am I doing something wrong?
Thanks,
Kyle |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Dec 09, 2010 2:12 pm |
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| I don't think a variable parameter is supported for the offset. |
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kda406
Joined: 17 Sep 2003
Posts: 97
Location: Atlanta, GA, USA
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| Posted: Thu Dec 09, 2010 2:32 pm |
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Thanks, that was my conclusion, but I don't see why they would not. It seems sophomoric to do: | Code: | iData[0] = make8(lPortBit[iCnt],0);
iData[1] = make8(lPortBit[iCnt],1);
iData[2] = make8(lPortBit[iCnt],2);
iData[3] = make8(lPortBit[iCnt],3); |
My professors would have laughed at me for forgetting how to do loops. 
Thanks,
Kyle |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19506
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| Posted: Thu Dec 09, 2010 3:52 pm |
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The problem is down to the nature of the function. It uses the simplest approach, to select the byte _efficiently_ at compile time. You can do it with a loop, using a union, or casting an int8 pointer to the memory you want to transfer, _but_ the variable version, will probably be about 3 or 4 times the size of all four of the single byte transfers, and slower too...
Best Wishes |
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