Sending and receiving data from DHT11 sensor

[EnMon]

Hi,
So let me state early on that I'm pretty new to Arduino and Programming in general.

Background
I have been able to test the Node and Gateway examples on my Moteino (Node) and Moteino USB(gateway), and it worked.
I also tried to run a sample code to read Temp and Humidity data from my DHT11 sensor(code attached) and I could view the information on the serial monitor of my Node.

Challenge: I am trying to send the 'Temp and Humidity' data from my Node to Gateway.



What I have done: I tried to merge the code for the "DHT11 test" (found sample code online) with the code for the "Node" in order to transmit the info to the "Gateway", but I keep getting the same "123  ABCDE..." data (that has been pre-coded for the gateway)on the serial monitor.

I need help modifying the sample codes for the "DHT11",  "Node" and "Gateway" in order to read the data from the serial monitor of my Gateway port.

PS: Any reference to past posts that have solved this issue would be appreciated, though I tried my best to read through lots of pages before asking for help.

Code Select Expand

//
//    FILE: dht11_test.ino
//  AUTHOR: Rob Tillaart
// VERSION: 0.1.00
// PURPOSE: DHT library test sketch for DHT11 && Arduino
//     URL:
//
// Released to the public domain
//

#include <dht.h>

dht DHT;

#define DHT11_PIN 5

void setup()
{
  Serial.begin(115200);
  Serial.println("DHT TEST PROGRAM ");
  Serial.print("LIBRARY VERSION: ");
  Serial.println(DHT_LIB_VERSION);
  Serial.println();
  Serial.println("Type,\tstatus,\tHumidity (%),\tTemperature (C)");
}

void loop()
{
  // READ DATA
  Serial.print("DHT11, \t");
  int chk = DHT.read11(DHT11_PIN);
  switch (chk)
  {
    case DHTLIB_OK:  
		Serial.print("OK,\t"); 
		break;
    case DHTLIB_ERROR_CHECKSUM: 
		Serial.print("Checksum error,\t"); 
		break;
    case DHTLIB_ERROR_TIMEOUT: 
		Serial.print("Time out error,\t"); 
		break;
    default: 
		Serial.print("Unknown error,\t"); 
		break;
  }
  // DISPLAY DATA
  Serial.print(DHT.humidity, 1);
  Serial.print(",\t");
  Serial.println(DHT.temperature, 1);

  delay(2000);
}
//
// END OF FILE
//

[Felix]

I never used DHT11 but looking briefly at the dht.h header, looks like the readings are doubles. So you have to sprintf those into a string and send them to your gateway moteino that way.

Here's a snippet of code from the WeatherNode example which does just that:

Code Select Expand

    char Pstr[10];     //<---- this holds your "double" as a string
    P = getPressure();
    P*=0.0295333727; //transform to inHg
    dtostrf(P, 3,2, Pstr);     //<------ convert double to a string with 2 decimals
    sprintf(buffer, "BAT:%sv F:%d H:%d P:%s", BATstr, weatherShield_SI7021.getFahrenheitHundredths(), weatherShield_SI7021.getHumidityPercent(), Pstr);

    sendLen = strlen(buffer);
    radio.sendWithRetry(GATEWAYID, buffer, sendLen, 1); //retry one time

The interesting lines are the dtostrf and sprintf, those are functions that package your various complex variables (strings, numbers) into a single buffer string, which then gets sent via radio. Hope this helps.

[EnMon]

Thanks Felix,
That was an eye opener for me(newbie in programming).
However I am experiencing error while compiling after making the changes you suggested.

Is there something I am doing wrong?

Code Select Expand

// Sample RFM69 sender/node sketch, with ACK and optional encryption, and Automatic Transmission Control
// Sends periodic messages of increasing length to gateway (id=1)
// It also looks for an onboard FLASH chip, if present
// RFM69 library and sample code by Felix Rusu - http://LowPowerLab.com/contact
// Copyright Felix Rusu (2015)

#include <RFM69.h>    //get it here: https://www.github.com/lowpowerlab/rfm69
#include <RFM69_ATC.h>//get it here: https://www.github.com/lowpowerlab/rfm69
#include <SPI.h>
#include <SPIFlash.h> //get it here: https://www.github.com/lowpowerlab/spiflash
#include <DHT.h>

#define DHTPIN 5     // what digital pin we're connected to
//*********************************************************************************************
//************ IMPORTANT SETTINGS - YOU MUST CHANGE/CONFIGURE TO FIT YOUR HARDWARE *************
//*********************************************************************************************
#define NODEID        2    //must be unique for each node on same network (range up to 254, 255 is used for broadcast)
#define NETWORKID     100  //the same on all nodes that talk to each other (range up to 255)
#define GATEWAYID     1
//Match frequency to the hardware version of the radio on your Moteino (uncomment one):
//#define FREQUENCY   RF69_433MHZ
//#define FREQUENCY   RF69_868MHZ
#define FREQUENCY     RF69_915MHZ
#define ENCRYPTKEY    "sampleEncryptKey" //exactly the same 16 characters/bytes on all nodes!
//#define IS_RFM69HW    //uncomment only for RFM69HW! Leave out if you have RFM69W!
#define ENABLE_ATC    //comment out this line to disable AUTO TRANSMISSION CONTROL
//*********************************************************************************************

#ifdef __AVR_ATmega1284P__
  #define LED           15 // Moteino MEGAs have LEDs on D15
  #define FLASH_SS      23 // and FLASH SS on D23
#else
  #define LED           9 // Moteinos have LEDs on D9
  #define FLASH_SS      8 // and FLASH SS on D8
#endif

#define DHTTYPE DHT11   // DHT 11
#define SERIAL_BAUD   115200


int TRANSMITPERIOD = 150; //transmit a packet to gateway so often (in ms)
char Tstr[10];
char buff[50];
byte sendSize=0;
byte sendLen=0;
boolean requestACK = false;
SPIFlash flash(FLASH_SS, 0xEF30); //EF30 for 4mbit  Windbond chip (W25X40CL)

#ifdef ENABLE_ATC
  RFM69_ATC radio;
#else
  RFM69 radio;
#endif

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(SERIAL_BAUD);
  Serial.println("DHTxx test!");

  dht.begin();
  radio.initialize(FREQUENCY,NODEID,NETWORKID);
#ifdef IS_RFM69HW
  radio.setHighPower(); //uncomment only for RFM69HW!
#endif
  radio.encrypt(ENCRYPTKEY);
  //radio.setFrequency(919000000); //set frequency to some custom frequency

//Auto Transmission Control - dials down transmit power to save battery (-100 is the noise floor, -90 is still pretty good)
//For indoor nodes that are pretty static and at pretty stable temperatures (like a MotionMote) -90dBm is quite safe
//For more variable nodes that can expect to move or experience larger temp drifts a lower margin like -70 to -80 would probably be better
//Always test your ATC mote in the edge cases in your own environment to ensure ATC will perform as you expect
#ifdef ENABLE_ATC
  radio.enableAutoPower(-70);
#endif

  char buffer[50];
  sprintf(buffer, "\nTransmitting at %d Mhz...", FREQUENCY==RF69_433MHZ ? 433 : FREQUENCY==RF69_868MHZ ? 868 : 915);
  Serial.println(buff);

  if (flash.initialize())
  {
    Serial.print("SPI Flash Init OK ... UniqueID (MAC): ");
    flash.readUniqueId();
    for (byte i=0;i<8;i++)
    {
      Serial.print(flash.UNIQUEID[i], HEX);
      Serial.print(' ');
    }
    Serial.println();
  }
  else
    Serial.println("SPI Flash MEM not found (is chip soldered?)...");

#ifdef ENABLE_ATC
  Serial.println("RFM69_ATC Enabled (Auto Transmission Control)\n");
#endif
}

void Blink(byte PIN, int DELAY_MS)
{
  pinMode(PIN, OUTPUT);
  digitalWrite(PIN,HIGH);
  delay(DELAY_MS);
  digitalWrite(PIN,LOW);
}

long lastPeriod = 0;


void loop() {
 
  float T = dht.readTemperature(true);
  // Read temperature as Fahrenheit (isFahrenheit = true)
  //float f = dht.readTemperature(true);

  // Check if any reads failed and exit early (to try again).
 // if (isnan(h) || isnan(t) || isnan(f)) {
  if (isnan(T)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  
    T = dht.readTemperature();
    dtostrf(T, 7,3, Tstr);
    sprintf(buffer,"T:%f",Tstr);

    sendLen = strlen(buffer);
    radio.sendWithRetry(GATEWAYID, buffer, sendLen, 1); //retry one time
    DEBUG(buffer); DEBUG(" (packet length:"); DEBUG(sendLen); DEBUGln(")");


 
  //process any serial input
  if (Serial.available() > 0)
  {
    char input = Serial.read();
    if (input >= 48 && input <= 57) //[0,9]
    {
      TRANSMITPERIOD = 100 * (input-48);
      if (TRANSMITPERIOD == 0) TRANSMITPERIOD = 1000;
      Serial.print("\nChanging delay to ");
      Serial.print(TRANSMITPERIOD);
      Serial.println("ms\n");
    }

    if (input == 'r') //d=dump register values
      radio.readAllRegs();
    //if (input == 'E') //E=enable encryption
    //  radio.encrypt(KEY);
    //if (input == 'e') //e=disable encryption
    //  radio.encrypt(null);

    if (input == 'd') //d=dump flash area
    {
      Serial.println("Flash content:");
      uint16_t counter = 0;

      Serial.print("0-256: ");
      while(counter<=256){
        Serial.print(flash.readByte(counter++), HEX);
        Serial.print('.');
      }
      while(flash.busy());
      Serial.println();
    }
    if (input == 'e')
    {
      Serial.print("Erasing Flash chip ... ");
      flash.chipErase();
      while(flash.busy());
      Serial.println("DONE");
    }
    if (input == 'i')
    {
      Serial.print("DeviceID: ");
      word jedecid = flash.readDeviceId();
      Serial.println(jedecid, HEX);
    }
  }

  //check for any received packets
  if (radio.receiveDone())
  {
    Serial.print('[');Serial.print(radio.SENDERID, DEC);Serial.print("] ");
    for (byte i = 0; i < radio.DATALEN; i++)
      Serial.print((char)radio.DATA[i]);
    Serial.print("   [RX_RSSI:");Serial.print(radio.RSSI);Serial.print("]");

    if (radio.ACKRequested())
    {
      radio.sendACK();
      Serial.print(" - ACK sent");
    }
    Blink(LED,3);
    Serial.println();
  }

  int currPeriod = millis()/TRANSMITPERIOD;
  if (currPeriod != lastPeriod)
  {
    lastPeriod=currPeriod;

    //send FLASH id
    if(sendSize==0)
    {
      sprintf(buff, "FLASH_MEM_ID:0x%X", flash.readDeviceId());
      byte buffLen=strlen(buff);
      if (radio.sendWithRetry(GATEWAYID, buff, buffLen))
        Serial.print(" ok!");
      else Serial.print(" nothing...");
      //sendSize = (sendSize + 1) % 31;
    }
    else
    {
      Serial.print("Sending[");
      Serial.print(sendSize);
      Serial.print("]: ");
      for(byte i = 0; i < sendSize; i++)
        Serial.print((char)Tstr[i]);

      if (radio.sendWithRetry(GATEWAYID, Tstr , sendSize))
       Serial.print(" ok!");
      else Serial.print(" nothing...");
    }
    sendSize = (sendSize + 1) % 31;
    Serial.println();
    Blink(LED,3);
  }
}

Error messages:

Node_editable:132: error: 'sendLen' was not declared in this scope

     sendLen = strlen(buffer);

     ^

Node_editable:132: error: 'buffer' was not declared in this scope

     sendLen = strlen(buffer);

                      ^

Node_editable:134: error: 'DEBUG' was not declared in this scope

     DEBUG(buffer); DEBUG(" (packet length:"); DEBUG(sendLen); DEBUGln(")");

                 ^

Node_editable:134: error: 'DEBUGln' was not declared in this scope

     DEBUG(buffer); DEBUG(" (packet length:"); DEBUG(sendLen); DEBUGln(")");

                                                                          ^

Thanks for your help!

[Felix]

You need to declare sendLen and buffer.

[EnMon]

Hello Felix,
I finally figured it out.  I found a way to convert the values to string before transmitting to the gateway.

Thanks for your response.
Really appreciate!

[Felix]

Great, I would suggest sharing your overall project and setup if you have the time, photos would be cool, so others like you would be encouraged to build similar nodes 

[EnMon]

Yes I plan to share as soon as everything is set.
Still working on some other parts of the project.