Slim Node Si7021 sensor example

[m26872]

@rsachoc Why don't you just solder some wires to pins you need ? The "in cicuit serial programming" concept would let you do it with almost anything attached.

[rsachoc]

@m26872 said:

@rsachoc Why don't you just solder some wires to pins you need ? The "in cicuit serial programming" concept would let you do it with almost anything attached.

I might as well attempt that! I'm waiting for a breadboard, so I'll try and attempt it when that arrives.

[rsachoc]

Some of my tips (noob alert) that I've gathered in my travels so far for this temp Slim node

1. Burn the bootloader onto the ATMega328 first! (here is a guide for Arduino as ISP)
2. Check the capacitor polarity before you solder it (the 4.7uF electrolytic capacitor, the others don't matter)
3. I prefer using strips for the Atmega (see here) as you'll have more clearance for the capacitors which sit underneath (there is a caveat to this however, in that if you're not sure if you've got/burnt a bootloader onto the ATMega, using strips there is no going back, whereas with the chip socket, you can remove the ATMega). Update I think, for me anyway, if you're confident that the ATMega has been bootloaded successfully, I still prefer strips, however if you're unsure what you can do is use the socket and just sit it higher in it's position to get a decent clearance.
4. The bill of materials (BOM) is here and also helps with figuring out which pieces go where
5. Solder the capacitors, wires for Si7021 (with si7021 attached) and FTDI pins to the board first, then the strips + AtMega328p (see below), then the NRF last to the board. I found that the FTDI pins facing straight up were best for the box I was going to put it in
6. Solder the strips to the ATMega first, then to the board
7. Check the size of the box/fitting you are going to mount this in before you do all the above!
8. Check that you are putting the ATMega chip the right way on the board, the notch should be facing the pins for the FTDI.
9. Check continuity of the pins from the ATMega to the board pins underneath, I found the ATMega to strips were the most difficult to solder, and after I tested continuity I found a single pin which didn't have connection, so I added some more solder to this pin.
10. Don't forget the resistor at R1 (I soldered this to the underside of the board, less by choice and more by the fact that I forgot about it, but I guess the preference would be the same side as the capacitors)
11. I strongly advise buying the 3.3v ready si7021 temp sensor (here) as the modification to the 5v version is quite difficult for a newbie (the components are quite small) and you'll probably mess it up like I did.

General soldering tips
12) Practice soldering first, some of the joins are a little challenging and it took me a few attempts to get the hang of it
13) Get a decent size tip, my first was a bit large

[GertSanders]

@rsachoc As a great man once said: "most bananas grow bent, and yet everyone loves them. There is nothing strange about the diversity of routes to success"

[rsachoc]

Thanks all, I'm sure I will be adding to it, as I'm now trying to compile and upload the sketch. However, I'm getting the following error:

   #error No forward link or gateway feature activated. This means nowhere to send messages! Pretty pointless.

    ^

exit status 1
Error compiling.

I'm using the W5100 MQTT gateway sketch (which I believe is on the development branch), so I'm not sure if that's what's causing the error? I've tried deleting the Arduino IDE, the mysensors development branch from my PC, and reinstalling and redownloading the mysensors dev branch, but the same thing happens?

[rsachoc]

OK, so it seems that it was because I was using the dev branch that I'm getting that error. I switched over to stable and the sketch compiles, although I do get a warning.

WARNING: Category '' in library UIPEthernet is not valid. Setting to 'Uncategorized'

But I also can't upload the sketch above:

avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x18

I noted above that something needed to be changed in terms of the baud rate, mine is set at 115200 in myconfig.h and I can't seem to find a reference in mysensor.h

[m26872]

@rsachoc I sorry, but there seems to be an error in the sketch in the first post. Baud rate should be 9600 everywhere if you use the common Slim Node fuses and bootloader. Upload (board.txt), MyConfig.h (not MySensor.h since v1.5), Debug-prints and Arduino IDE serial monitor.

[rsachoc]

Thanks, I've updated the sketch that I downloaded, also myconfig.h so that should be good. What do I need to select in the Arduino IDE for board type? I searched in the slim node thread and didn't see a reference to any changes?

[m26872]

@rsachoc No changes. It is that boards.txt entry you should use.

[rsachoc]

Hmmm ok, that's what I thought...still no luck, I've modified the boards.txt with the text from the slim node thread, and now it still has the same error message.

To confirm, my FTDI adaptor is attached to the board pins as follows:

FTDI <-> board
GND <-> first pin (i.e bottom left of board when looking at board laying long side horizontal and NRF radio on the other side)
CTS <-> board marked GND
PWR <-> board marked VCC
TXO <-> next up i.e. 4th pin
RXI <-> next up i.e. 5th pin
DTR <-> next up i.e. last pin

Other than that, I guess it may be something wrong with the way I made the board? If so, what's the best way to troubleshoot? Could it be a bad bootloader flash? Is there a way to check if the ATMega has a bootloader?

edit in fact, it could be because I don't have the Si7021 connected? Could this be the reason a sketch is not uploading successfully? :worried:

[m26872]

@rsachoc Start simple. Try on a board without nRF and sensors. Remove everything in the sketch and make it to just print "Hello world" back to serial monitor.

[rsachoc]

Thanks, I haven't actually built a new node, but have been double checking everything on my current node. One thing I wanted to confirm, the 4.7uf capacitor, does the negative leg have to be on the corner of the board, as this is the way I have it currently? I think looking at the board layout in the main slim node thread, it should be the positive leg on the corner and the negative leg on the side of the board (the short side of the board)?

[m26872]

@rsachoc I don't have it in front of me rigth now... but, there should be an arc and a super-small "+"-sign next to the positive pad. Maybe it just look like a dot.

[rsachoc]

Ok so that may be the problem then! Let me solder it the right way and see if that helps otherwise I'm going to create a bare bones slim mode as suggested

edit to confirm the positive leg of the capacitor goes to the positive marked plus sign hole on the board?

[rsachoc]

OK so I changed the polarity of the 4.7uf capacitor and I'm still receiving the same error. So I built a barebones one without sensor and without NRF. I am still getting the same error when uploading the sketch via the FTDI adaptor. I tried uploading a sketch to a Sensebender I have and it worked fine, so that rules out the FTDI adaptor.

Some pics in case someone can spot something obvious.

http://i.imgur.com/1SV0qO2.jpg

http://i.imgur.com/mUp87hB.jpg

http://i.imgur.com/oCqcDpo.jpg

So I can only think that it must be related to the ATMega bootloader? In the how to burn a bootloader thread, I received the following when trying to burn the bootloader, so I assumed it uploaded correctly?

C:\Users\James\Desktop\RPi Openhab\arduino-1.6.7-windows\hardware\tools\avr/bin/avrdude -CC:\Users\James\Desktop\RPi Openhab\arduino-1.6.7-windows\hardware\tools\avr/etc/avrdude.conf -v -patmega328p -cstk500v1 -PCOM5 -b19200 -e -Ulock:w:0x3F:m -Uefuse:w:0x05:m -Uhfuse:w:0xDE:m -Ulfuse:w:0xFF:m 

avrdude: Version 6.0.1, compiled on Apr 15 2015 at 19:59:58
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2009 Joerg Wunsch

         System wide configuration file is "C:\Users\James\Desktop\RPi Openhab\arduino-1.6.7-windows\hardware\tools\avr/etc/avrdude.conf"

         Using Port                    : COM5
         Using Programmer              : stk500v1
         Overriding Baud Rate          : 19200
         AVR Part                      : ATmega328P
         Chip Erase delay              : 9000 us
         PAGEL                         : PD7
         BS2                           : PC2
         RESET disposition             : dedicated
         RETRY pulse                   : SCK
         serial program mode           : yes
         parallel program mode         : yes
         Timeout                       : 200
         StabDelay                     : 100
         CmdexeDelay                   : 25
         SyncLoops                     : 32
         ByteDelay                     : 0
         PollIndex                     : 3
         PollValue                     : 0x53
         Memory Detail                 :

                                  Block Poll               Page                       Polled
           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack
           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
           eeprom        65    20     4    0 no       1024    4      0  3600  3600 0xff 0xff
           flash         65     6   128    0 yes     32768  128    256  4500  4500 0xff 0xff
           lfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           hfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           efuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           lock           0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           calibration    0     0     0    0 no          1    0      0     0     0 0x00 0x00
           signature      0     0     0    0 no          3    0      0     0     0 0x00 0x00

         Programmer Type : STK500
         Description     : Atmel STK500 Version 1.x firmware
         Hardware Version: 2
         Firmware Version: 1.18
         Topcard         : Unknown
         Vtarget         : 0.0 V
         Varef           : 0.0 V
         Oscillator      : Off
         SCK period      : 0.1 us

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.02s

avrdude: Device signature = 0x1e950f
avrdude: erasing chip
avrdude: reading input file "0x3F"
avrdude: writing lock (1 bytes):

Writing | ################################################## | 100% 0.01s

avrdude: 1 bytes of lock written
avrdude: verifying lock memory against 0x3F:
avrdude: load data lock data from input file 0x3F:
avrdude: input file 0x3F contains 1 bytes
avrdude: reading on-chip lock data:

C:\Users\James\Desktop\RPi Openhab\arduino-1.6.7-windows\hardware\tools\avr/bin/avrdude -CC:\Users\James\Desktop\RPi Openhab\arduino-1.6.7-windows\hardware\tools\avr/etc/avrdude.conf -v -patmega328p -cstk500v1 -PCOM5 -b19200 -Uflash:w:C:\Users\James\Desktop\RPi Openhab\arduino-1.6.7-windows\hardware\arduino\avr/bootloaders/optiboot/optiboot_atmega328.hex:i -Ulock:w:0x0F:m 
Reading | ################################################## | 100% 0.01s

avrdude: verifying ...
avrdude: 1 bytes of lock verified
avrdude: reading input file "0x05"
avrdude: writing efuse (1 bytes):

Writing | ################################################## | 100% 0.01s

avrdude: 1 bytes of efuse written
avrdude: verifying efuse memory against 0x05:
avrdude: load data efuse data from input file 0x05:
avrdude: input file 0x05 contains 1 bytes
avrdude: reading on-chip efuse data:

Reading | ################################################## | 100% 0.01s

avrdude: verifying ...
avrdude: 1 bytes of efuse verified
avrdude: reading input file "0xDE"
avrdude: writing hfuse (1 bytes):

Writing | ################################################## | 100% 0.01s

avrdude: 1 bytes of hfuse written
avrdude: verifying hfuse memory against 0xDE:
avrdude: load data hfuse data from input file 0xDE:
avrdude: input file 0xDE contains 1 bytes
avrdude: reading on-chip hfuse data:

Reading | ################################################## | 100% 0.01s

avrdude: verifying ...
avrdude: 1 bytes of hfuse verified
avrdude: reading input file "0xFF"
avrdude: writing lfuse (1 bytes):

Writing | ################################################## | 100% 0.01s

avrdude: 1 bytes of lfuse written
avrdude: verifying lfuse memory against 0xFF:
avrdude: load data lfuse data from input file 0xFF:
avrdude: input file 0xFF contains 1 bytes
avrdude: reading on-chip lfuse data:

Reading | ################################################## | 100% 0.01s

avrdude: verifying ...
avrdude: 1 bytes of lfuse verified

avrdude done.  Thank you.


avrdude: Version 6.0.1, compiled on Apr 15 2015 at 19:59:58
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2009 Joerg Wunsch

         System wide configuration file is "C:\Users\James\Desktop\RPi Openhab\arduino-1.6.7-windows\hardware\tools\avr/etc/avrdude.conf"

         Using Port                    : COM5
         Using Programmer              : stk500v1
         Overriding Baud Rate          : 19200
         AVR Part                      : ATmega328P
         Chip Erase delay              : 9000 us
         PAGEL                         : PD7
         BS2                           : PC2
         RESET disposition             : dedicated
         RETRY pulse                   : SCK
         serial program mode           : yes
         parallel program mode         : yes
         Timeout                       : 200
         StabDelay                     : 100
         CmdexeDelay                   : 25
         SyncLoops                     : 32
         ByteDelay                     : 0
         PollIndex                     : 3
         PollValue                     : 0x53
         Memory Detail                 :

                                  Block Poll               Page                       Polled
           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack
           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
           eeprom        65    20     4    0 no       1024    4      0  3600  3600 0xff 0xff
           flash         65     6   128    0 yes     32768  128    256  4500  4500 0xff 0xff
           lfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           hfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           efuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           lock           0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           calibration    0     0     0    0 no          1    0      0     0     0 0x00 0x00
           signature      0     0     0    0 no          3    0      0     0     0 0x00 0x00

         Programmer Type : STK500
         Description     : Atmel STK500 Version 1.x firmware
         Hardware Version: 2
         Firmware Version: 1.18
         Topcard         : Unknown
         Vtarget         : 0.0 V
         Varef           : 0.0 V
         Oscillator      : Off
         SCK period      : 0.1 us

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.02s

avrdude: Device signature = 0x1e950f
avrdude: NOTE: "flash" memory has been specified, an erase cycle will be performed
         To disable this feature, specify the -D option.
avrdude: erasing chip
avrdude: reading input file "C:\Users\James\Desktop\RPi Openhab\arduino-1.6.7-windows\hardware\arduino\avr/bootloaders/optiboot/optiboot_atmega328.hex"
avrdude: writing flash (32768 bytes):

Writing | ################################################## | 100% 0.00s

avrdude: 32768 bytes of flash written
avrdude: verifying flash memory against C:\Users\James\Desktop\RPi Openhab\arduino-1.6.7-windows\hardware\arduino\avr/bootloaders/optiboot/optiboot_atmega328.hex:
avrdude: load data flash data from input file C:\Users\James\Desktop\RPi Openhab\arduino-1.6.7-windows\hardware\arduino\avr/bootloaders/optiboot/optiboot_atmega328.hex:
avrdude: input file C:\Users\James\Desktop\RPi Openhab\arduino-1.6.7-windows\hardware\arduino\avr/bootloaders/optiboot/optiboot_atmega328.hex contains 32768 bytes
avrdude: reading on-chip flash data:

Reading | ################################################## | 100% -0.00s

avrdude: verifying ...
avrdude: 32768 bytes of flash verified
avrdude: reading input file "0x0F"
avrdude: writing lock (1 bytes):

Writing | ################################################## | 100% 0.02s

avrdude: 1 bytes of lock written
avrdude: verifying lock memory against 0x0F:
avrdude: load data lock data from input file 0x0F:
avrdude: input file 0x0F contains 1 bytes
avrdude: reading on-chip lock data:

Reading | ################################################## | 100% 0.01s

avrdude: verifying ...
avrdude: 1 bytes of lock verified

avrdude done.  Thank you.

[m26872]

@rsachoc Looks like you're missing the R1 resistor?

[rsachoc]

@m26872 well that is probably it! I didn't even realise I needed that, oops! Sorry :disappointed: ! Let me try and get one (I think I have some already) and get soldering

[rsachoc]

It lives! Well the one node I created does at least! I'll troubleshoot it, but the problem was the R1 resistor, which I (noobishly) forgot about! But very pleased, and thanks to m26872 especially and everyone else who helped.

I've updated the lessons learn post too!

[rsachoc]

I just received my non-3.3v Si7021, and have now updated the lessons learnt post, as this board is tiny and I managed to mess up the soldering completely. Ordered the 3.3 ready version now, another month wait...

[siod]

@carlierd said:

@ar91 Please find the code I used in 3 different nodes. The good thing with the playground lib is that there is error message if dialog with DHT22 failed.

/**
 * The MySensors Arduino library handles the wireless radio link and protocol
 * between your home built sensors/actuators and HA controller of choice.
 * The sensors forms a self healing radio network with optional repeaters. Each
 * repeater and gateway builds a routing tables in EEPROM which keeps track of the
 * network topology allowing messages to be routed to nodes.
 *
 * Created by Henrik Ekblad <henrik.ekblad@mysensors.org>
 * Copyright (C) 2013-2015 Sensnology AB
 * Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
 *
 * Documentation: http://www.mysensors.org
 * Support Forum: http://forum.mysensors.org
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 */

/**************************************************************************************/
/* Temperature, humidity and luminosity measurements.                                 */
/*                                                                                    */
/* Version     : 1.1.6                                                                */
/* Date        : 10/01/2016                                                           */
/* Modified by : David Carlier                                                        */
/**************************************************************************************/
/*                                ---------------                                     */
/*                            RST |             |  A5                                 */
/*                            RX  |             |  A4                                 */
/*                            TX  |   ARDUINO   |  A3                                 */
/*     RFM69 (DIO0) --------- D2  |     UNO     |  A2                                 */
/*            DHT22 --------- D3  |             |  A1                                 */
/*            Power --------- D4  | ATMEGA 328p |  A0 --------- Light dep. resistor   */
/*              +3v --------- VCC |             | GND --------- GND                   */
/*              GND --------- GND |  8MHz int.  | REF                                 */
/*                            OSC |             | VCC --------- +3v                   */
/*                            OSC |             | D13 --------- RFM69 (SCK)           */
/*                            D5  |             | D12 --------- RFM69 (MISO)          */
/*                            D6  |             | D11 --------- RFM69 (MOSI)          */
/*                            D7  |             | D10 --------- RFM69 (NSS)           */
/*                            D8  |             |  D9                                 */
/*                                ---------------                                     */
/*                                                                                    */
/* Power = Vcc for LDR.                                                               */
/* +3v = 2*AA                                                                         */
/*                                                                                    */
/**************************************************************************************/

#include <SPI.h>
#include <MySensor.h>
#include <dht.h>
#include <MyTransportRFM69.h>
#include <MySigningAtsha204Soft.h>

#define CHILD_ID_HUM 0
#define CHILD_ID_TEMP 1
#define CHILD_ID_LIGHT 2
#define CHILD_ID_VOLTAGE 3
#define LIGHT_SENSOR_ANALOG_PIN 0
#define HUMIDITY_SENSOR_DIGITAL_PIN 3
#define POWER_PIN 4
//unsigned long SLEEP_TIME = 850000; // Sleep time between reads (in milliseconds) (close to 15')
unsigned long SLEEP_TIME = 275000; // Sleep time between reads (in milliseconds) (close to 5')

//Construct MySensors library
MySigningAtsha204Soft signer;
MyHwATMega328 hw;
MyTransportRFM69 transport;
MySensor gw(transport, hw, signer);
dht DHT;
MyMessage msgHum(CHILD_ID_HUM, V_HUM);
MyMessage msgTemp(CHILD_ID_TEMP, V_TEMP);
MyMessage msgLum(CHILD_ID_LIGHT, V_LEVEL);
MyMessage msgVolt(CHILD_ID_VOLTAGE, V_VOLTAGE);

/**************************************************************************************/
/* Initialization                                                                     */
/**************************************************************************************/
void setup()
  {
  //Get time (for setup duration)
  #ifdef DEBUG
    unsigned long startTime = millis();
  #endif

  //Start MySensors
  gw.begin();

  //Send the Sketch Version Information to the Gateway
  gw.sendSketchInfo("GHAS sensor", "1.1.5");

  //Register all sensors to gw (they will be created as child devices)
  gw.present(CHILD_ID_HUM, S_HUM);
  gw.present(CHILD_ID_TEMP, S_TEMP);
  gw.present(CHILD_ID_LIGHT, S_LIGHT_LEVEL);
  gw.present(CHILD_ID_VOLTAGE, S_MULTIMETER);

  //Delay for DHT22
  delay(1500);

  //Print setup debug
  #ifdef DEBUG
    int duration = millis() - startTime;
    Serial.print("[Setup duration: "); Serial.print(duration, DEC); Serial.println(" ms]");
  #endif
  }

/**************************************************************************************/
/* Main loop                                                                          */
/**************************************************************************************/
void loop()
  {
  //Get time (for a complete loop)
  #ifdef DEBUG
    unsigned long startTime = millis();
  #endif

  //Power on
  powerOnPeripherals();

  //Get DHT22 data
  int dht22Result = DHT.read22(HUMIDITY_SENSOR_DIGITAL_PIN);
  switch (dht22Result)
    {
    case DHTLIB_OK:  
                //Serial.println("OK,\t");
                break;
    case DHTLIB_ERROR_CHECKSUM:
                #ifdef DEBUG
                  Serial.println("Checksum error,\t");
                #endif
                break;
    case DHTLIB_ERROR_TIMEOUT:
                #ifdef DEBUG
                  Serial.println("Time out error,\t");
                #endif
                break;
    case DHTLIB_ERROR_CONNECT:
                #ifdef DEBUG
                  Serial.println("Connect error,\t");
                #endif
                break;
    case DHTLIB_ERROR_ACK_L:
                #ifdef DEBUG
                  Serial.println("Ack Low error,\t");
                #endif
                break;
    case DHTLIB_ERROR_ACK_H:
                #ifdef DEBUG
                  Serial.println("Ack High error,\t");
                #endif
                break;
    default:
                #ifdef DEBUG
                  Serial.println("Unknown error,\t");
                #endif
                break;
    }

  //Get temperature and humidity
  float temperature = 0;
  float humidity = 0;
  if (dht22Result == DHTLIB_OK)
    {
    temperature = DHT.temperature;
    humidity = DHT.humidity;
    }

  //Get power before luminosity to use real voltage
  float realVoltage = getVoltage() / 100.0;
  int batteryPcnt = realVoltage * 100 / 3.0;
  if (batteryPcnt > 100) {batteryPcnt = 100;}
  int lux = computeIlluminance(realVoltage);

  //Power off
  powerOffPeripherals();

  //Send data to gateway
  gw.send(msgHum.set(humidity, 1));
  gw.send(msgTemp.set(temperature, 1));
  gw.send(msgLum.set(lux));
  gw.send(msgVolt.set(realVoltage, 2));
  gw.sendBatteryLevel(batteryPcnt);

  //Print debug
  #ifdef DEBUG
    Serial.print(temperature, 1);
    Serial.print(" degC");
    Serial.print("   ");
    Serial.print(humidity, 1);
    Serial.print(" %");
    Serial.print("   ");
    Serial.print(lux);
    Serial.print(" lx");
    Serial.print("   ");
    Serial.print(realVoltage);
    Serial.print(" v");
    int duration = millis() - startTime;
    Serial.print("   ");
    Serial.print("["); Serial.print(duration, DEC); Serial.println(" ms]");
    Serial.flush();
  #endif

  //Sleep
  gw.sleep(SLEEP_TIME);
  }

/**************************************************************************************/
/* Allows to compute illuminance (in LUX) from LIGHT_SENSOR_ANALOG_PIN.               */
/**************************************************************************************/
int computeIlluminance(float realVoltage)
  {
  //Get luminosity
  int luminosity = analogRead(LIGHT_SENSOR_ANALOG_PIN);
  //Calculating the voltage in the input of the ADC
  double voltage = realVoltage * ((double)luminosity / 1024.0);
  //Calculating the resistance of the photoresistor in the voltage divider
  double resistance = (10.0 * realVoltage) / voltage - 10.0;
  //Calculating the intensity of light in lux and return it
  int illuminance = 255.84 * pow(resistance, -10/9);
  return illuminance;
  }

/**************************************************************************************/
/* Allows to get the real Vcc (return value * 100).                                   */
/**************************************************************************************/
int getVoltage()
  {
  const long InternalReferenceVoltage = 1056L;
  ADMUX = (0<<REFS1) | (1<<REFS0) | (0<<ADLAR) | (1<<MUX3) | (1<<MUX2) | (1<<MUX1) | (0<<MUX0);
  delay(50);  // Let mux settle a little to get a more stable A/D conversion
  //Start a conversion  
  ADCSRA |= _BV( ADSC );
  //Wait for it to complete
  while (((ADCSRA & (1<<ADSC)) != 0));
  //Scale the value
  int result = (((InternalReferenceVoltage * 1023L) / ADC) + 5L) / 10L;
  return result;
  }

/**************************************************************************************/
/* Allows to power ON peripherals.                                                    */
/**************************************************************************************/
void powerOnPeripherals()
  {
  //Power-up
  pinMode (POWER_PIN, OUTPUT);
  digitalWrite (POWER_PIN, HIGH);
  delay(1);
  }

/**************************************************************************************/
/* Allows to power OFF peripherals.                                                   */
/**************************************************************************************/
void powerOffPeripherals()
  {
  //Power off
  digitalWrite (HUMIDITY_SENSOR_DIGITAL_PIN, LOW);
  digitalWrite (POWER_PIN, LOW);
  pinMode (HUMIDITY_SENSOR_DIGITAL_PIN, INPUT);
  pinMode (POWER_PIN, INPUT);
  }

Hope it helps !

David.

So the DHT22 works at 1MHz with 2 AAs and your code you´ve posted? No physical differnces?