Motorola USB08 - Manual (Page 118)

Designer Reference Manual USB08 Evaluation Board
118 Source Code Files MOTOROLA
Source Code Files
// *** calibration cycle ***
PTD &= ~0x78; // PTD[3..6] = L
DDRD |= 0x78; // Output
PTE |= 0x07; // PTE[0..2] = H;
DDRE |= 0x07; // Output
for(zz=0;zz<1000;zz--) ;
DDRE &= ~0x07; // PTE HiZ (Input)
t0 = TCNT;
while((PTE & channel) != 0) ;
t1 = TCNT;
t1 -= t0;
// *** acquisition cycle ***
DDRD &= ~0x38; // PTD[3..5] = HiZ
DDRE |= 0x07; // Output
for(zz=0;zz<1000;zz--) ;
DDRE &= ~0x07; // PTE HiZ (Input)
t0 = TCNT;
while((PTE & channel) != 0) ;
t2 = TCNT;
t2 = t2 - t0 - t1 - 100;
if(t2 > 50000u) t2=0; // underflow
if(t2 >= t1) t2 = t1-1; // overflow
// *** calculate scaled result ***
t2 = scaleSADC(t1,t2);
return t2;
}
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