My program is going off into the weeds, and in an odd fashion. I hope someone can spot my error. I have a table of sine values stored as a const in flash. The table is 2048 16-bit entries. Here is the routine that uses the table:
unsigned int ConvertToSin(unsigned long thisPhase)
{
unsigned int quarterPhase;
unsigned int thisQuarter;
unsigned int thisSample;
unsigned int dummySample;
quarterPhase = (thisPhase>>19) & 0x7FF; //bottom 11 bits please
thisQuarter = thisPhase>>30; //top two bits is the quarter
thisQuarter = thisQuarter & 0x03; //limit to 2 bits
switch(thisQuarter) {
case 0:
thisSample=sine_table[quarterPhase];
break;
case 1:
thisSample=sine_table[(0x7FF-quarterPhase)];
break;
case 2:
thisSample=0xFFF-sine_table[quarterPhase];
break;
case 3:
thisSample=0xFFF-sine_table[(0x7FF-quarterPhase)];
break;
default:
thisSample = 0;
}
return thisSample;
//return 0;
}Here is the sine table declaration:
const __flash uint16_t sine_table[] = {
0x0800,
0x0801,
0x0803,
0x0804,
..
..
0x0FFF,
0x0FFF,
0x0FFF,
0x0FFF }; // 2048 entries
When this routine gets executed my target stops running, and when I pause the debugger the program counter is in the sine table!
If I remove the references to quarterPhase in the sine_table reads and use constants it works. I don't see how running off the end of an array would cause what I am seeing.
I have tried using PROGMEM instead of __flash with the same results. Also I have another table that is the same size but is 1K of long words and it works just fine.
Any help would be appreciated.
--tr
