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Save 1k code space by using TaylorSeries log function 

Save 1k code space by using TaylorSeries log function
This commit is contained in:
Theo Arends 2019-05-18 18:24:17 +02:00
parent 5515a97be6
commit 052cfbc11d
2 changed files with 19 additions and 1 deletions
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18
sonoff/support.ino
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@ -680,6 +680,24 @@ float FastPrecisePowf(const float x, const float y)
return (float)FastPrecisePow(x, y);
}
double TaylorLog(double x)
{
// https://stackoverflow.com/questions/46879166/finding-the-natural-logarithm-of-a-number-using-taylor-series-in-c
double z = (x + 1) / (x - 1); // We start from power -1, to make sure we get the right power in each iteration;
double step = ((x - 1) * (x - 1)) / ((x + 1) * (x + 1)); // Store step to not have to calculate it each time
double totalValue = 0;
double powe = 1;
double y;
for (int count = 0; count < 10; count++) {
z *= step;
y = (1 / powe) * z;
totalValue = totalValue + y;
powe = powe + 2;
}
return 2 * totalValue;
}
uint32_t SqrtInt(uint32_t num)
{
if (num <= 1) {

2
sonoff/xsns_02_analog.ino
View File

@ -100,7 +100,7 @@ void AdcEverySecond(void)
int adc = AdcRead(2);
// Steinhart-Hart equation for thermistor as temperature sensor
double Rt = (adc * ANALOG_NTC_BRIDGE_RESISTANCE) / (1024.0 * ANALOG_V33 - (double)adc);
double T = ANALOG_NTC_B_COEFFICIENT / (ANALOG_NTC_B_COEFFICIENT / ANALOG_T0 + log(Rt / ANALOG_NTC_RESISTANCE));
double T = ANALOG_NTC_B_COEFFICIENT / (ANALOG_NTC_B_COEFFICIENT / ANALOG_T0 + TaylorLog(Rt / ANALOG_NTC_RESISTANCE));
adc_temp = ConvertTemp(TO_CELSIUS(T));
}
}