DHT library error

[pbecchi]

I get a compilation error using dht.h lib:

Arduino:1.6.5 (Windows 8.1), Scheda:"NodeMCU 0.9 (ESP-12 Module), 80 MHz, 115200"

d:/users/pbecc/appdata/roaming/arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/1.20.0-26-gb404fb9/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libm.a(lib_a-w_sqrt.o):(.literal+0x8): undefined reference to __ieee754_sqrt' d:/users/pbecc/appdata/roaming/arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/1.20.0-26-gb404fb9/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libm.a(lib_a-w_sqrt.o): In functionsqrt':
d:\ivan\projects\arduinoesp\toolchain\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libm\math/../../../../../newlib/libm/math/w_sqrt.c:63: undefined reference to `__ieee754_sqrt'
collect2.exe: error: ld returned 1 exit status

The library call the sqrt() math function : this give the error( no error commenting out the line!)

[ebeechsrc]

The compiler doesn't support sqrt, log or pow which are used in the dew point part of this library. If you remove the dewpoint.h and reference the DHT11.h directly to get the relative humidity and temperature it will work.

I believe a less precise approximation of dew point temperature in Centigrade is temp - ((100 - relative humidity)/5)

[asetyde]

My dht library on nodemcu 1.0 work perfectly . My library not call sqrt

[pbecchi]

The DHT library contain a module:

float DHT::computeHeatIndex(....
This module call sqrt and pow math function.
Of course if you don't use it there is no problem with unsupported math!

As 10to7 said, there is simpler way to calculate dew point that don't involve the use of those functions.

I used the library example that call "computeHeatIndex" : I dont normally use this function.

To simplify the library it may be possible to rewrite Dewpoint calculation and also to use integer ( in term of 0,1 °F or °C) rather than floating values!!

[asetyde]

i use heatindex on bodemcu with dht library , with 0 problems

On 04 nov 2015, at 18:00, pbecchi notifications@github.com wrote:

The DHT library contain a module:

float DHT::computeHeatIndex(....
This module call sqrt and pow math function.
Of course if you don't use it there is no problem with unsupported math!

As 10to7 said, there is simpler way to calculate dew point that don't involve the use of those functions.

I used the library example that call "computeHeatIndex" : I dont normally use this function.

To simplify the library it may be possible to rewrite Dewpoint calculation and also to use integer ( in term of 0,1 °F or °C) rather than floating values!!

—
Reply to this email directly or view it on GitHub #940 (comment).

[pbecchi]

I use the Adafruit DHT library! It look like this:

float DHT::computeHeatIndex(float temperature, float percentHumidity, bool isFahrenheit) {
// Using both Rothfusz and Steadman's equations
// http://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml
float hi;

if (!isFahrenheit)
temperature = convertCtoF(temperature);

hi = 0.5 * (temperature + 61.0 + ((temperature - 68.0) * 1.2) + (percentHumidity * 0.094));

if (hi > 79) {
hi = -42.379 +
2.04901523 * temperature +
10.14333127 * percentHumidity +
-0.22475541 * temperature_percentHumidity +
-0.00683783 * pow(temperature, 2) +
-0.05481717 * pow(percentHumidity, 2) +
0.00122874 * pow(temperature, 2) * percentHumidity +
0.00085282 * temperature_pow(percentHumidity, 2) +
-0.00000199 * pow(temperature, 2) * pow(percentHumidity, 2);

if((percentHumidity < 13) && (temperature >= 80.0) && (temperature <= 112.0))
  hi -= ((13.0 - percentHumidity) * 0.25) */* sqrt*/((17.0 - abs(temperature - 95.0)) * 0.05882);

else if((percentHumidity > 85.0) && (temperature >= 80.0) && (temperature <= 87.0))
  hi += ((percentHumidity - 85.0) * 0.1) * ((87.0 - temperature) * 0.2);

}

return isFahrenheit ? hi : convertFtoC(hi);
}

[asetyde]

do you use last version ?

On 04 nov 2015, at 18:06, pbecchi notifications@github.com wrote:

I use the Adafruit DHT library! It look like this:

float DHT::computeHeatIndex(float temperature, float percentHumidity, bool isFahrenheit) {
// Using both Rothfusz and Steadman's equations
// http://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml http://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml
float hi;

if (!isFahrenheit)
temperature = convertCtoF(temperature);

hi = 0.5 * (temperature + 61.0 + ((temperature - 68.0) * 1.2) + (percentHumidity * 0.094));

if (hi > 79) {
hi = -42.379 +
2.04901523 * temperature +
10.14333127 * percentHumidity +
-0.22475541 * temperaturepercentHumidity +
-0.00683783 * pow(temperature, 2) +
-0.05481717 * pow(percentHumidity, 2) +
0.00122874 * pow(temperature, 2) * percentHumidity +
0.00085282 * temperaturepow(percentHumidity, 2) +
-0.00000199 * pow(temperature, 2) * pow(percentHumidity, 2);

if((percentHumidity < 13) && (temperature >= 80.0) && (temperature <= 112.0))
hi -= ((13.0 - percentHumidity) * 0.25) / sqrt*/((17.0 - abs(temperature - 95.0)) * 0.05882);

else if((percentHumidity > 85.0) && (temperature >= 80.0) && (temperature <= 87.0))
hi += ((percentHumidity - 85.0) * 0.1) * ((87.0 - temperature) * 0.2);
}

return isFahrenheit ? hi : convertFtoC(hi);
}

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[pbecchi]

Your library is probably different..... look at the your source!

[asetyde]

Use version 1.1.1 and i think ti will go

On 04 nov 2015, at 18:11, pbecchi notifications@github.com wrote:

Your library is probably different..... look at the your source!

—
Reply to this email directly or view it on GitHub #940 (comment).

[pbecchi]

Thank's!!
It is important to know that those math functions cannot be used!

[asetyde]

ok start from this and go up , after says to community ( i don’t try because in my 3000 lines of code i’m afraid :)) but if some new version work is a good idea upgrade

On 04 nov 2015, at 18:15, pbecchi notifications@github.com wrote:

Thank's!!
It is important to know that those math functions cannot be used!

—
Reply to this email directly or view it on GitHub #940 (comment).

[asetyde]

adafruit/DHT-sensor-library#45

[asetyde]

last supported release 1.2.0 , at now i ll try to find a solution

[asetyde]

please reopen issue