DHT22, AM2302 and pic18F2320

[Demon]

Well this guy got it working in C after playing with delays so it's most likely a timing issue.

18F2320 can run at 40MHz internally, I'd try that first. Others mention waiting at least 2 seconds between samples.

http://forum.43oh.com/topic/2239-sol...or-on-energia/

Robert

[bitmaniac]

SUCCESS!!!

After trying to increase crystal to 25Mhz and also 40Mhz I had the same problem of grabing only the first 21 pulses.... (problems with PULSIN speed...hmm....)

Finally the solution was just to use PULSIN 40 times! in my code and not use the FOR NEXT LOOP !

So there was timming speed problems and had to improve my code for speed - a little...

Now I am getting correct results

Here is the final code (the only thing left is to check checksum for errors!) ENJOY.

'***************************************
'*  Name    : 18f2320_DHT22_AM2302.BAS *
'*  Author  : bitmaniac   Alexandros Z.*
'*  Notice  : Copyright (c) 2013       *
'*  Date    : 5/4/2013                 *
'***************************************

;include "ALLDIGITAL.pbp"
;@ __CONFIG _CONFIG1H, _INTIO2_OSC_1H & _IESO_OFF_1H ' use internal osc
@ __CONFIG _CONFIG1H, _HS_OSC_1H & _IESO_OFF_1H ' use internal osc
@ __CONFIG _CONFIG2L, _PWRT_OFF_2L & _BOR_OFF_2L
@ __CONFIG _CONFIG2H, _WDT_OFF_2H & _WDTPS_512_2H
@ __CONFIG _CONFIG3H, _MCLRE_OFF_3H & _PBAD_DIG_3H ;& _CCP2MX_OFF_3H
@ __CONFIG _CONFIG4L, _LVP_OFF_4L

DEFINE  LCD_DREG        PORTC	' LCD Data Port
DEFINE  LCD_DBIT        4		' Starting Data Bit
DEFINE  LCD_RSREG       PORTC	' Register Select Port
DEFINE  LCD_RSBIT       2		' Register Select Bit
DEFINE  LCD_RWREG       PORTC   ' LCD read/write port 
DEFINE  LCD_RWBIT       1       ' LCD read/write bit 
DEFINE  LCD_EREG        PORTC	' Enable Port
DEFINE  LCD_EBIT        0		' Enable Bit
DEFINE  LCD_BITS		4		' Data Bus Size
DEFINE  LCD_LINES		2		' Number of Lines on LCD
DEFINE  LCD_COMMANDUS 2000
DEFINE  LCD_DATAUS 50
pause 300

define osc 4

ADCON0=0 
ADCON1=00001111                  'All digital
CMCON=7                          'Comparators OFF
INTCON2.7=0                      'RBPU =0 , TURN ON PORTB PULL-UPS

TRISA=%00000000
TRISB=%00001111

PORTA=0
PORTB=0

humread     var word             '16-bit var to store humidity
tmpread     var word             '16-bit var to store temperature
checksum    var BYTE             '8-bit var to store checksum
x           var byte             'general var
pulse       var byte [81]        'store pulse var
p           var bit [81]         'store pulse var

led         var LATA.0
dht_port    var PORTB.4

clear
high dht_port
high led

;---------- main program -------------
high led
LCDout $FE,$01,"DHT-22"
LCDout $FE,$C0,"testing..."
pause 2000

start:
;---- check_DHT22 ----
;-== send StartSignal ==-
TRISB.4 = 0                      'Data port is output
high dht_port
pauseus 10                       'send 10uS high pulse
low dht_port                     
pause 1                          'send 1mS high pulse
high dht_port
;-== wait response from Sensor ==-
TRISB.4 = 1                      'Data port is input
while dht_port=1:wend            'wait for low from DHT
while dht_port=0:wend            'wait for high FROM DHT
high led
;-== Grab 40bits data from DHT22 ==-
pulsin PORTB.4,1,pulse(1)        'Humidity HighBit data
pulsin PORTB.4,1,pulse(2)
pulsin PORTB.4,1,pulse(3)
pulsin PORTB.4,1,pulse(4)
pulsin DHT_port,1,pulse(5)
pulsin DHT_port,1,pulse(6)
pulsin DHT_port,1,pulse(7)
pulsin DHT_port,1,pulse(8)
pulsin DHT_port,1,pulse(9)
pulsin DHT_port,1,pulse(10)
pulsin DHT_port,1,pulse(11)
pulsin DHT_port,1,pulse(12)
pulsin DHT_port,1,pulse(13)
pulsin DHT_port,1,pulse(14)
pulsin DHT_port,1,pulse(15)
pulsin DHT_port,1,pulse(16)      'Humidity LowBit data
pulsin DHT_port,1,pulse(17)      'Temperature HighBit data (1 means below 0 degree!)
pulsin DHT_port,1,pulse(18)
pulsin DHT_port,1,pulse(19)
pulsin DHT_port,1,pulse(20)
pulsin DHT_port,1,pulse(21)
pulsin DHT_port,1,pulse(22)
pulsin DHT_port,1,pulse(23)
pulsin DHT_port,1,pulse(24)
pulsin DHT_port,1,pulse(25)
pulsin DHT_port,1,pulse(26)
pulsin DHT_port,1,pulse(27)
pulsin DHT_port,1,pulse(28)
pulsin DHT_port,1,pulse(29)
pulsin DHT_port,1,pulse(30)
pulsin DHT_port,1,pulse(31)
pulsin DHT_port,1,pulse(32)      'Temperature LowBit data
;pulsin DHT_port,1,pulse(33)     'Checksum HighBit
;pulsin DHT_port,1,pulse(34)
;pulsin DHT_port,1,pulse(35)
;pulsin DHT_port,1,pulse(36)
;pulsin DHT_port,1,pulse(37)
;pulsin DHT_port,1,pulse(38)
;pulsin DHT_port,1,pulse(39)
;pulsin DHT_port,1,pulse(40)     'Checksum LowBit
;-== convert to '0' & '1' ==-
for x=1 to 40
if pulse(x)>=2 and pulse(x)<=4 then p(x)=0 'if pulsewidth between 20 and 40uS then read as '0' 
if pulse(x)>=6 and pulse(x)<=8 then p(x)=1 'if pulsewidth between 60 and 80uS then read as '1'
next x
;-== convert bin to dec ==-
humread=32768*p(1)+16384*p(2)+8192*p(3)+4096*p(4)+2048*p(5)+1024*p(6)+512*p(7)+256*p(8)+128*p(9)+64*p(10)+32*p(11)+16*p(12)+8*p(13)+4*p(14)+2*p(15)+1*p(16)
tmpread=16384*p(18)+8192*p(19)+4096*p(20)+2048*p(21)+1024*p(22)+512*p(23)+256*p(24)+128*p(25)+64*p(26)+32*p(27)+16*p(28)+8*p(29)+4*p(30)+2*p(31)+1*p(32)
;checksum=128*p(33)+64*p(34)+32*p(35)+16*p(36)+8*p(37)+4*p(38)+2*p(39)+1*p(40)
;-== show real values ==-
LCDout $FE,$01,"RHdata  Tdata"
LCDout $FE,$C0,dec humread/10,".",dec humread//10,"%   ",dec tmpread/10,".",dec tmpread//10,"oC" 'print integral part only
low led
pause 2000                       'give some time to DHT to stabilize!....
goto start
END

Finnally I would like to say A BIG THANK YOU to demon for sending me the correct infos to search about that helped me to pinpoint my problem!

[Demon]

Congrats! Did you comfirm the readings with another device? Looks a little hot and dry where you live.

Robert

[Acetronics2]

Hi, Alexandros

did you find this one?
http://embedded-lab.com/blog/?p=4333

interesting explanations there.

BTW ... How are you ???

Alain

[bitmaniac]

@ Demon I have not yet tested with another device... The photo wa taken before sensor given time to settle (as soon as I switched on!)

@Acetronics Hi! my good friend! There has been a looong time since my last visit here! (Actually for the last year I was working on my retro collection hobby with local retro-exchibitions etc!)
Yes I have seen this site infos....

[rodrik]

Hi,

I want to use those codes to read values each 15 minutes via serial port. I need two sensors to read. One on board , the second 10 meters of wire. To replace LCD codes to serial is very easy. I wonder the include "ALLDIGITAL.pbp" not shown here . Finally what's is oscillator frequency ?

The last version of PBP codes, seems from 5'th April 2013

Thanks

[Archangel]

Get it here: http://www.picbasic.co.uk/forum/cont...54-All-Digital

First post OSC 4