Error compiling DHT11

Using Arduino Programming Questions
1

Hi All, Not sure if this is posted in the right forum?
I'm getting the following errors, any help would be appreciated :slight_smile:

"C:\Users\Scott\AppData\Local\Temp\ccVZ3FeX.ltrans0.ltrans.o: In function `loop':"

"C:\Users\Scott\Downloads\dht11A/dht11A.ino:80: undefined reference to `dht11::read(int)'

collect2.exe:"
error: ld returned 1 exit status

exit status 1
Error compiling for board Arduino/Genuino Uno.

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.
Arduino: 1.8.3 (Windows 10), Board: "Arduino/Genuino Uno"

Here is the my sketch:

//
// FILE: dht11_test1.pde
// PURPOSE: DHT11 library test sketch for Arduino
//

//Celsius to Fahrenheit conversion
double Fahrenheit(double celsius)
{
return 1.8 * celsius + 32;
}

// fast integer version with rounding
//int Celcius2Fahrenheit(int celcius)
//{
// return (celsius * 18 + 5)/10 + 32;
//}

//Celsius to Kelvin conversion
double Kelvin(double celsius)
{
return celsius + 273.15;
}

// dewPoint function NOAA
// reference (1) : Algorithms - Schlatter and Baker
// reference (2) : http://www.colorado.edu/geography/weather_station/Geog_site/about.htm
//
double dewPoint(double celsius, double humidity)
{
// (1) Saturation Vapor Pressure = ESGG(T)
double RATIO = 373.15 / (273.15 + celsius);
double RHS = -7.90298 * (RATIO - 1);
RHS += 5.02808 * log10(RATIO);
RHS += -1.3816e-7 * (pow(10, (11.344 * (1 - 1/RATIO ))) - 1) ;
RHS += 8.1328e-3 * (pow(10, (-3.49149 * (RATIO - 1))) - 1) ;
RHS += log10(1013.246);

// factor -3 is to adjust units - Vapor Pressure SVP * humidity
double VP = pow(10, RHS - 3) * humidity;

// (2) DEWPOINT = F(Vapor Pressure)
double T = log(VP/0.61078); // temp var
return (241.88 * T) / (17.558 - T);
}

// delta max = 0.6544 wrt dewPoint()
// 6.9 x faster than dewPoint()
// reference: Dew point - Wikipedia
double dewPointFast(double celsius, double humidity)
{
double a = 17.271;
double b = 237.7;
double temp = (a * celsius) / (b + celsius) + log(humidity*0.01);
double Td = (b * temp) / (a - temp);
return Td;
}

#include <dht11.h>

dht11 DHT11;

#define DHT11PIN 2

void setup()
{
Serial.begin(115200);
Serial.println("DHT11 TEST PROGRAM ");
Serial.print("LIBRARY VERSION: ");
Serial.println(DHT11LIB_VERSION);
Serial.println();
}

void loop()
{
Serial.println("\n");

int chk = DHT11.read(DHT11PIN);

Serial.print("Read sensor: ");
switch (chk)
{
case DHTLIB_OK:
Serial.println("OK");
break;
case DHTLIB_ERROR_CHECKSUM:
Serial.println("Checksum error");
break;
case DHTLIB_ERROR_TIMEOUT:
Serial.println("Time out error");
break;
default:
Serial.println("Unknown error");
break;
}

Serial.print("Humidity (%): ");
Serial.println((float)DHT11.humidity, 2);

Serial.print("Temperature (°C): ");
Serial.println((float)DHT11.temperature, 2);

Serial.print("Temperature (°F): ");
Serial.println(Fahrenheit(DHT11.temperature), 2);

Serial.print("Temperature (°K): ");
Serial.println(Kelvin(DHT11.temperature), 2);

Serial.print("Dew Point (°C): ");
Serial.println(dewPoint(DHT11.temperature, DHT11.humidity));

Serial.print("Dew PointFast (°C): ");
Serial.println(dewPointFast(DHT11.temperature, DHT11.humidity));

delay(2000);
}
//
// END OF FILE
//

2

Please put your code in code tags, it's hurting my eyes. Also, it's a general convention that you should put the "#include" and variable definitions at the top of your code, not at the bottom. I had to do a Ctrl+F to find the #include line. From your error message it appears that the function "read(int)" doesn't exist in the library. I'd suggest using this guide which has a link to the Adafruit DHT sensor library, which is extremely easy to use. Your code seems awfully complicated.