DHT22 (sensor) to Pachube via Arduino with Ethernet shield error - networking

Question

I'm trying to connect a DHT22 sensor to the Pachube online service.
I am understanding the code and have everything wired up correctly but I get this error:
DHT22 Library Demo
Requesting data at 6335
Sync Timeout
What does sync timeout mean? Is is a network problem?
How could I fix this?
Here is my code anyway:
/* Feed temperature and humidity to Pachube.
Based on the following examples:
Sample code from nethoncho's DHT22 library:
https://github.com/nethoncho/Arduino-DHT22
Tom Igoe's PachubeClient:
http://arduino.cc/en/Tutorial/PachubeCient
*/
#include <DHT22.h>
#include <SPI.h>
#include <Ethernet.h>
// Data wire is plugged into port 7 on the Arduino
// Connect a 4.7K resistor between VCC and the data pin (strong pullup)
#define DHT22_PIN 2
// Setup a DHT22 instance
DHT22 myDHT22(DHT22_PIN);
static unsigned long lWaitMillis;
// assign a MAC address for the ethernet controller.
// fill in your address here:
byte mac[] = {
0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED};
// assign an IP address for the controller:
byte ip[] = {
192,168,0,30 };
byte gateway[] = {
192,168,1,2};
byte subnet[] = {
255, 255, 255, 0 };
// The address of the server you want to connect to (pachube.com):
byte server[] = {
173,203,98,29 };
// initialize the library instance:
Client client(server, 80);
boolean lastConnected = false; // state of the connection last time through the main loop
const long postingInterval = 180000; //delay between updates to Pachube.com
int backoff = 0;
void setup(void)
{
// start serial port
Serial.begin(9600);
Serial.println("DHT22 Library Demo");
// start the ethernet connection:
Ethernet.begin(mac, ip);
// give the ethernet module time to boot up:
delay(1000);
lWaitMillis = millis() + 5000;
}
void loop() {
// if there's incoming data from the net connection.
// send it out the serial port. This is for debugging
// purposes only:
if (client.available()) {
char c = client.read();
Serial.print(c);
}
// if there's no net connection, but there was one last time
// through the loop, then stop the client:
if (!client.connected() && lastConnected) {
Serial.println();
Serial.println("disconnecting.");
client.stop();
while(client.status() != 0) {
Serial.print("Client status: ");
Serial.println(client.status());
delay(5);
}
}
// if you're not connected, and ten seconds have passed since
// your last connection, then connect again and send data:
if(!client.connected() && (long)( millis() - lWaitMillis ) >= 0 ) {
if (readData()) {
int temp = myDHT22.getTemperatureC();
int humidity = myDHT22.getHumidity() + .5;
sendData(temp, humidity);
}
lWaitMillis += postingInterval;
if (lWaitMillis < millis()) {
lWaitMillis = millis() + postingInterval;
}
Serial.print("Next attempt at ");
Serial.println(lWaitMillis);
Serial.println();
}
// store the state of the connection for next time through
// the loop:
lastConnected = client.connected();
}
boolean readData()
{
DHT22_ERROR_t errorCode;
Serial.print("Requesting data at ");
Serial.println(millis());
errorCode = myDHT22.readData();
switch(errorCode)
{
case DHT_ERROR_NONE:
Serial.print("Got Data ");
Serial.print(myDHT22.getTemperatureC());
Serial.print("C ");
Serial.print(myDHT22.getHumidity());
Serial.println("%");
return true;
break;
case DHT_ERROR_CHECKSUM:
Serial.print("check sum error ");
Serial.print(myDHT22.getTemperatureC());
Serial.print("C ");
Serial.print(myDHT22.getHumidity());
Serial.println("%");
break;
case DHT_BUS_HUNG:
Serial.println("BUS Hung ");
break;
case DHT_ERROR_NOT_PRESENT:
Serial.println("Not Present ");
break;
case DHT_ERROR_ACK_TOO_LONG:
Serial.println("ACK time out ");
break;
case DHT_ERROR_SYNC_TIMEOUT:
Serial.println("Sync Timeout ");
break;
case DHT_ERROR_DATA_TIMEOUT:
Serial.println("Data Timeout ");
break;
case DHT_ERROR_TOOQUICK:
Serial.println("Polled too quick ");
break;
}
return false;
}
// this method makes a HTTP connection to the server:
void sendData(int temp, int humidity) {
// if there's a successful connection:
if (client.connect()) {
backoff = 0;
Serial.println("connecting...");
// send the HTTP PUT request.
// fill in your feed address here:
client.print("PUT /v2/feeds/36800.csv HTTP/1.1\n");
client.print("Host: api.pachube.com\n");
// fill in your Pachube API key here:
client.print("X-PachubeApiKey: a6714b6a217827edadfd003843c03c259a08add554eda3871b844612eddc6819\n");
client.print("Content-Length: ");
// calculate the length of the sensor reading in bytes:
int thisLength = 2 + getLength(temp) + 2 + 2 + getLength(humidity);
client.println(thisLength, DEC);
// last pieces of the HTTP PUT request:
client.print("Content-Type: text/csv\n");
client.println("Connection: close\n");
// here's the actual content of the PUT request:
client.print(0, DEC);
client.print(",");
client.println(temp, DEC);
client.print(1, DEC);
client.print(",");
client.println(humidity, DEC);
}
else {
// if you couldn't make a connection:
Serial.println("connection failed, resetting.");
Ethernet.begin(mac, ip);
delay(1000);
client.stop();
delay(1000);
}
}
// This method calculates the number of digits in the
// sensor reading. Since each digit of the ASCII decimal
// representation is a byte, the number of digits equals
// the number of bytes:
int getLength(int someValue) {
// there's at least one byte:
int digits = 1;
// continually divide the value by ten,
// adding one to the digit count for each
// time you divide, until you're at 0:
int dividend = someValue /10;
while (dividend > 0) {
dividend = dividend /10;
digits++;
}
// return the number of digits:
return digits;
}

Answer 1

You're running into DHT_ERROR_SYNC_TIMEOUT sensor error, that means that the DHT sensor is running into some sync problem, I guess.
What arduino are you using? Is your board's frequence 8 or 16Mhz?
Give a try to the edit described here, too. If it still doesn't work, I would try using sensor itself (i.e. without connecting to patchube) with some test sketch you can easily find for DHT22, just to make sure the sensor is working properly.

Answer 2

I had similar problem when using Arduino Nano v3.0 + ENC28J60 Ethernet shield. I tried to connect RF receiver to digital PIN #2 but this never worked.
Then I used different pin for the RF module (PIN #4 in my case) and everything worked fine.