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Fix for #415 sin/cos integer overflow on 16-bit CPUs #416

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merged 7 commits into from
Jul 18, 2024
Merged

Fix for #415 sin/cos integer overflow on 16-bit CPUs #416

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241e8c0
LinearHall improvements and move to main repository
dekutree64 Jan 14, 2024
aeb9238
Minor formatting/comment edits
dekutree64 Jan 14, 2024
41de6b6
Moving LinearHall back to drivers repository
dekutree64 Feb 14, 2024
3a84021
Moving LinearHall back to drivers repository
dekutree64 Feb 14, 2024
e81af5d
Fix for #415 sin/cos integer overflow on 16-bit CPUs
dekutree64 Jun 29, 2024
bf75d20
Removed accidental addition of LinearHall.h
dekutree64 Jun 29, 2024
b203b83
Merge branch 'dev' into dev
dekutree64 Jun 29, 2024
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11 changes: 6 additions & 5 deletions src/common/foc_utils.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9,20 +9,21 @@ __attribute__((weak)) float _sin(float a){
// 16 bit precision on sine value, 8 bit fractional value for interpolation, 6bit LUT size
// resulting precision compared to stdlib sine is 0.00006480 (RMS difference in range -PI,PI for 3217 steps)
static uint16_t sine_array[65] = {0,804,1608,2411,3212,4011,4808,5602,6393,7180,7962,8740,9512,10279,11039,11793,12540,13279,14010,14733,15447,16151,16846,17531,18205,18868,19520,20160,20788,21403,22006,22595,23170,23732,24279,24812,25330,25833,26320,26791,27246,27684,28106,28511,28899,29269,29622,29957,30274,30572,30853,31114,31357,31581,31786,31972,32138,32286,32413,32522,32610,32679,32729,32758,32768};
int32_t t1, t2;
unsigned int i = (unsigned int)(a * (64*4*256.0f/_2PI));
int t1, t2, frac = i & 0xff;
int frac = i & 0xff;
i = (i >> 8) & 0xff;
if (i < 64) {
t1 = sine_array[i]; t2 = sine_array[i+1];
t1 = (int32_t)sine_array[i]; t2 = (int32_t)sine_array[i+1];
}
else if(i < 128) {
t1 = sine_array[128 - i]; t2 = sine_array[127 - i];
t1 = (int32_t)sine_array[128 - i]; t2 = (int32_t)sine_array[127 - i];
}
else if(i < 192) {
t1 = -sine_array[-128 + i]; t2 = -sine_array[-127 + i];
t1 = -(int32_t)sine_array[-128 + i]; t2 = -(int32_t)sine_array[-127 + i];
}
else {
t1 = -sine_array[256 - i]; t2 = -sine_array[255 - i];
t1 = -(int32_t)sine_array[256 - i]; t2 = -(int32_t)sine_array[255 - i];
}
return (1.0f/32768.0f) * (t1 + (((t2 - t1) * frac) >> 8));
}
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