Arduino 1.0 and DHT22 library

Projects Programming
1

I tried to set up such a sensor with the library from GitHub - nethoncho/Arduino-DHT22: Arduino library for the DHT22 humidity and temperature sensor. First had to change the inclusion of WConstants.h to Arduino.h since I understood it has changed in recent Arduino versions.
But the example still wont compile, I get these error messages:

In file included from /home/jskata/arduino-1.0/hardware/arduino/cores/arduino/Arduino.h:191,
                 from /home/jskata/arduino-1.0/libraries/DHT22/DHT22.cpp:47:
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/WString.h:116: error: declaration of C function ‘StringSumHelper& operator+(const StringSumHelper&, const char*)’ conflicts with
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/WString.h:115: error: previous declaration ‘StringSumHelper& operator+(const StringSumHelper&, const String&)’ here
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/WString.h:117: error: declaration of C function ‘StringSumHelper& operator+(const StringSumHelper&, char)’ conflicts with
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/WString.h:116: error: previous declaration ‘StringSumHelper& operator+(const StringSumHelper&, const char*)’ here
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/WString.h:118: error: declaration of C function ‘StringSumHelper& operator+(const StringSumHelper&, unsigned char)’ conflicts with
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/WString.h:117: error: previous declaration ‘StringSumHelper& operator+(const StringSumHelper&, char)’ here
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/WString.h:119: error: declaration of C function ‘StringSumHelper& operator+(const StringSumHelper&, int)’ conflicts with
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/WString.h:118: error: previous declaration ‘StringSumHelper& operator+(const StringSumHelper&, unsigned char)’ here
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/WString.h:120: error: declaration of C function ‘StringSumHelper& operator+(const StringSumHelper&, unsigned int)’ conflicts with
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/WString.h:119: error: previous declaration ‘StringSumHelper& operator+(const StringSumHelper&, int)’ here
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/WString.h:121: error: declaration of C function ‘StringSumHelper& operator+(const StringSumHelper&, long int)’ conflicts with
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/WString.h:120: error: previous declaration ‘StringSumHelper& operator+(const StringSumHelper&, unsigned int)’ here
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/WString.h:122: error: declaration of C function ‘StringSumHelper& operator+(const StringSumHelper&, long unsigned int)’ conflicts with
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/WString.h:121: error: previous declaration ‘StringSumHelper& operator+(const StringSumHelper&, long int)’ here
In file included from /home/jskata/arduino-1.0/libraries/DHT22/DHT22.cpp:47:
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/Arduino.h:195: error: declaration of C function ‘uint16_t makeWord(byte, byte)’ conflicts with
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/Arduino.h:194: error: previous declaration ‘uint16_t makeWord(uint16_t)’ here
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/Arduino.h:205: error: declaration of C function ‘long int random(long int)’ conflicts with
/usr/lib/gcc/avr/4.3.5/../../../avr/include/stdlib.h:504: error: previous declaration ‘long int random()’ here
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/Arduino.h:206: error: declaration of C function ‘long int random(long int, long int)’ conflicts with
/home/jskata/arduino-1.0/hardware/arduino/cores/arduino/Arduino.h:205: error: previous declaration ‘long int random(long int)’ here

This is under KUbuntu with an Uno.

2

First had to change the inclusion of WConstants.h to Arduino.h since I understood it has changed in recent Arduino versions.
But the example still wont compile, I get these error messages:

No. WProgram.h was renamed to Arduino.h.

3

This post does say it is replaced by Arduino.h: Google Code Archive - Long-term storage for Google Code Project Hosting.

4

Got it working.
Changed in DHT22.cpp

extern "C" {
#include "WConstants.h"
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/pgmspace.h>
}

into

#include "Arduino.h"
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/pgmspace.h>
5

Thank you. I have been searching for the solution for most of the night.

6

I have a problem of showing the temperature and humidity online in a web page. The example bellow works perfectly outputing data to serial doesn't work printing data to web clients. How should I format the output to be usable for html. The temperature and humidity are float types. The way I print now makes the web page to crash and show error on loading.

DHT22_ERROR_t errorCode;
              delay(2000);
              errorCode = myDHT22.readData();
              switch(errorCode)
              {
                case DHT_ERROR_NONE:
                  client.print("<tr><td>Temperature</td><td>D</td><td>");
                  client.print(digitalChannel);
                  client.print("</td><td>");
                  client.write(myDHT22.getTemperatureC());
                  client.print(" C</td></tr>");
                  client.print("<tr><td>Humidity</td><td>D</td><td>");
                  client.print(digitalChannel);
                  client.print("</td><td>");
                  client.write(myDHT22.getHumidity());
                  client.print(" %</td></tr>");
               ....
            }
7

What values do myDHT22.getTemperatureC() and myDHT22.getHumidity() return. Where I am at the moment, the temperature is 18 degrees C. You are using client.write(), which sends the byte unaltered. If you send ASCII 18 (Device Control 2) to a web-browser, how should it display it?

8

If you send ASCII 18 (Device Control 2) to a web-browser, how should it display it?

Sending "18" (ASCII 18) should not be a problem. That is NOT what the code is sending, though. It is sending the binary value of 18 to the client. Clients rarely understand what to do with binary data.

OP: You should most likely NOT be using client.write(). You should be using client.print() to send the temperature and humidity as strings.

9

What's the difference between the ascii character DC2 (0x12, Decimal 18) and binary value 18 (0x12)? I didn't say "18", I said Device Control 2.

10

What's the difference between

Nothing. I was just trying to point out that print() converts 18 to "18" to send, but that write() does not, in a little less subtle way than you did.

11

Problem solved. Seems that all it was necessary was a hard reset of the arduino. Afterwards all works fine as for the output.