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Shrink sensors code size by 5k using local pow

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This commit is contained in:
Theo Arends 2020-05-15 14:17:11 +02:00
parent 6573802f83
commit bafe8a137f
1 changed files with 95 additions and 71 deletions
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40
lib/Mutichannel_Gas_Sensor/src/MutichannelGasSensor.cpp
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@ -327,6 +327,30 @@ int16_t MutichannelGasSensor::readR(void)
** Returns: ** Returns:
float value - concentration of the gas float value - concentration of the gas
*********************************************************************************************************/ *********************************************************************************************************/
float MutichannelGasSensor_pow(float a, float b)
{
// https://martin.ankerl.com/2012/01/25/optimized-approximative-pow-in-c-and-cpp/
// calculate approximation with fraction of the exponent
int e = abs((int)b);
union {
double d;
int x[2];
} u = { a };
u.x[1] = (int)((b - e) * (u.x[1] - 1072632447) + 1072632447);
u.x[0] = 0;
// exponentiation by squaring with the exponent's integer part
// double r = u.d makes everything much slower, not sure why
double r = 1.0;
while (e) {
if (e & 1) {
r *= a;
}
a *= a;
e >>= 1;
}
return r * u.d;
}
float MutichannelGasSensor::calcGas(int gas) float MutichannelGasSensor::calcGas(int gas)
{ {
@ -370,42 +394,42 @@ float MutichannelGasSensor::calcGas(int gas)
{ {
case CO: case CO:
{ {
c = pow(ratio1, -1.179)*4.385; //mod by jack c = MutichannelGasSensor_pow(ratio1, -1.179)*4.385; //mod by jack
break; break;
} }
case NO2: case NO2:
{ {
c = pow(ratio2, 1.007)/6.855; //mod by jack c = MutichannelGasSensor_pow(ratio2, 1.007)/6.855; //mod by jack
break; break;
} }
case NH3: case NH3:
{ {
c = pow(ratio0, -1.67)/1.47; //modi by jack c = MutichannelGasSensor_pow(ratio0, -1.67)/1.47; //modi by jack
break; break;
} }
case C3H8: //add by jack case C3H8: //add by jack
{ {
c = pow(ratio0, -2.518)*570.164; c = MutichannelGasSensor_pow(ratio0, -2.518)*570.164;
break; break;
} }
case C4H10: //add by jack case C4H10: //add by jack
{ {
c = pow(ratio0, -2.138)*398.107; c = MutichannelGasSensor_pow(ratio0, -2.138)*398.107;
break; break;
} }
case GAS_CH4: //add by jack case GAS_CH4: //add by jack
{ {
c = pow(ratio1, -4.363)*630.957; c = MutichannelGasSensor_pow(ratio1, -4.363)*630.957;
break; break;
} }
case H2: //add by jack case H2: //add by jack
{ {
c = pow(ratio1, -1.8)*0.73; c = MutichannelGasSensor_pow(ratio1, -1.8)*0.73;
break; break;
} }
case C2H5OH: //add by jack case C2H5OH: //add by jack
{ {
c = pow(ratio1, -1.552)*1.622; c = MutichannelGasSensor_pow(ratio1, -1.552)*1.622;
break; break;
} }
default: default: