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add private pow function in lib for future use 

alternate pow function for future use in Tasmota to calculate normalized Lux and normalized white values.
This commit is contained in:
device111 2020-05-24 12:28:08 +02:00
parent 43b999600e
commit ebbbd37865
2 changed files with 31 additions and 2 deletions
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27
lib/Adafruit_VEML7700/Adafruit_VEML7700.cpp
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@ -76,6 +76,29 @@ boolean Adafruit_VEML7700::begin(TwoWire *theWire) {
return true;
}
float Adafruit_VEML7700::alternate_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 Adafruit_VEML7700::normalize_resolution(float value) {
// adjust for gain (1x is normalized)
@ -123,7 +146,7 @@ float Adafruit_VEML7700::readLuxNormalized() {
// user-provided correction for non-linearities at high lux/white values:
// https://forums.adafruit.com/viewtopic.php?f=19&t=152997&p=758582#p759346
if ((getGain() == VEML7700_GAIN_1_8) && (getIntegrationTime() == VEML7700_IT_25MS)){
lux = 6.0135e-13*pow(lux,4) - 9.3924e-9*pow(lux,3) + 8.1488e-5*pow(lux,2) + 1.0023*lux;
lux = 6.0135e-13*alternate_pow(lux,4) - 9.3924e-9*alternate_pow(lux,3) + 8.1488e-5*alternate_pow(lux,2) + 1.0023*lux;
}
return lux;
@ -156,7 +179,7 @@ float Adafruit_VEML7700::readWhiteNormalized() {
// user-provided correction for non-linearities at high lux values:
// https://forums.adafruit.com/viewtopic.php?f=19&t=152997&p=758582#p759346
if ((getGain() == VEML7700_GAIN_1_8) && (getIntegrationTime() == VEML7700_IT_25MS)){
white = 2E-15*pow(white,4) + 4E-12*pow(white,3) + 9E-06*pow(white,2) + 1.0179*white - 11.052;
white = 2E-15*alternate_pow(white,4) + 4E-12*alternate_pow(white,3) + 9E-06*alternate_pow(white,2) + 1.0179*white - 11.052;
}
return white;

6
lib/Adafruit_VEML7700/Adafruit_VEML7700.h
View File

@ -14,6 +14,11 @@
* BSD license (see license.txt)
*/
/*
* change from device111 for Tasmota
* Add alternativ Pow function for readLuxNormalized() and readWhiteNormalized()
*/
#ifndef _ADAFRUIT_VEML7700_H
#define _ADAFRUIT_VEML7700_H
@ -105,6 +110,7 @@ private:
*PowerSave_Enable, *PowerSave_Mode;
float normalize_resolution(float value);
float alternate_pow(float a, float b);
Adafruit_I2CDevice *i2c_dev;