DHT22, AM2302 and pic18F2320

[bitmaniac]

P is defined as byte, but referred as bit?

It should be byte as it stores the width of the pulse (in uS) PULSIN receives.
Then it simply stores on itself the value of '1' or '0' according the width of this pulse.

Edit: what if you display the data you receive, pause a few seconds, then continue. Confirm you're getting data as you expect it.

Hmm! I will give it a try and let you knoiw ....Good thoughts my friend!

Edit 2: Does your array start at 0 or 1? (Haven't coded in a while).

I don't think is matter... Arrays start at 0.

Only 17 entries for temp, missing #17.

I just try to not capture the higher bit of temp (1 means temp is below 0 degrees Celsius) for the moment just testing....

Robert Thank you very much for replying

As I can see no example ANYWHERE in the net for DHT22 and picbasic , when completed it would be a good starting point for experiments with this low cost sensor!

[bitmaniac]

In order to find out what pulsin really grabs I used serout data to debug...
Here are the results so far -after reading the sensor 3 times.... :
NOTE I changed the code a little bit so I can capture all data (included the start transmit 1bit before each 'bit')

* * * START * * *
01=> 50uS  bit_val= 1
02=> 20uS  bit_val= 0
03=> 50uS  bit_val= 1
04=> 30uS  bit_val= 1
05=> 50uS  bit_val= 1
06=> 70uS  bit_val= 1
07=> 50uS  bit_val= 1
08=> 70uS  bit_val= 1
09=> 50uS  bit_val= 1
10=> 20uS  bit_val= 0
11=> 50uS  bit_val= 1
12=> 30uS  bit_val= 1
13=> 50uS  bit_val= 1
14=> 20uS  bit_val= 0
15=> 50uS  bit_val= 1
16=> 30uS  bit_val= 1
17=> 70uS  bit_val= 1
18=> 20uS  bit_val= 0
19=> 50uS  bit_val= 1
20=> 60uS  bit_val= 0
21=> 50uS  bit_val= 1
22=> 70uS  bit_val= 1
23=> 50uS  bit_val= 1
24=> 30uS  bit_val= 1
25=> 50uS  bit_val= 1
26=> 20uS  bit_val= 0
27=> 50uS  bit_val= 1
28=> 0uS  bit_val= 0
29=> 0uS  bit_val= 0
30=> 0uS  bit_val= 0
31=> 0uS  bit_val= 0
32=> 0uS  bit_val= 0
33=> 0uS  bit_val= 0
34=> 0uS  bit_val= 0
35=> 0uS  bit_val= 0
36=> 0uS  bit_val= 0
37=> 0uS  bit_val= 0
38=> 0uS  bit_val= 0
39=> 0uS  bit_val= 0
40=> 0uS  bit_val= 0
41=> 0uS  bit_val= 0
42=> 0uS  bit_val= 0
43=> 0uS  bit_val= 0
44=> 0uS  bit_val= 0
45=> 0uS  bit_val= 0
46=> 0uS  bit_val= 0
47=> 0uS  bit_val= 0
48=> 0uS  bit_val= 0
49=> 0uS  bit_val= 0
50=> 0uS  bit_val= 0
51=> 0uS  bit_val= 0
52=> 0uS  bit_val= 0
53=> 0uS  bit_val= 0
54=> 0uS  bit_val= 0
55=> 0uS  bit_val= 0
56=> 0uS  bit_val= 0
57=> 0uS  bit_val= 0
58=> 0uS  bit_val= 0
59=> 0uS  bit_val= 0
60=> 0uS  bit_val= 0
61=> 0uS  bit_val= 0
62=> 0uS  bit_val= 0
63=> 0uS  bit_val= 0
64=> 0uS  bit_val= 0
65=> 0uS  bit_val= 0
66=> 0uS  bit_val= 0
67=> 0uS  bit_val= 0
68=> 0uS  bit_val= 0
69=> 0uS  bit_val= 0
70=> 0uS  bit_val= 0
71=> 0uS  bit_val= 0
72=> 0uS  bit_val= 0
73=> 0uS  bit_val= 0
74=> 0uS  bit_val= 0
75=> 0uS  bit_val= 0
76=> 0uS  bit_val= 0
77=> 0uS  bit_val= 0
78=> 0uS  bit_val= 0
79=> 0uS  bit_val= 0
80=> 0uS  bit_val= 0
* * * END * * *

* * * START * * *
01=> 50uS  bit_val= 1
02=> 20uS  bit_val= 0
03=> 50uS  bit_val= 1
04=> 30uS  bit_val= 1
05=> 50uS  bit_val= 1
06=> 70uS  bit_val= 1
07=> 50uS  bit_val= 1
08=> 70uS  bit_val= 1
09=> 50uS  bit_val= 1
10=> 20uS  bit_val= 0
11=> 50uS  bit_val= 1
12=> 30uS  bit_val= 1
13=> 50uS  bit_val= 1
14=> 20uS  bit_val= 0
15=> 50uS  bit_val= 1
16=> 20uS  bit_val= 0
17=> 70uS  bit_val= 1
18=> 20uS  bit_val= 0
19=> 50uS  bit_val= 1
20=> 70uS  bit_val= 1
21=> 50uS  bit_val= 1
22=> 60uS  bit_val= 0
23=> 50uS  bit_val= 1
24=> 30uS  bit_val= 1
25=> 50uS  bit_val= 1
26=> 20uS  bit_val= 0
27=> 50uS  bit_val= 1
28=> 0uS  bit_val= 0
29=> 0uS  bit_val= 0
30=> 0uS  bit_val= 0
31=> 0uS  bit_val= 0
32=> 0uS  bit_val= 0
33=> 0uS  bit_val= 0
34=> 0uS  bit_val= 0
35=> 0uS  bit_val= 0
36=> 0uS  bit_val= 0
37=> 0uS  bit_val= 0
38=> 0uS  bit_val= 0
39=> 0uS  bit_val= 0
40=> 0uS  bit_val= 0
41=> 0uS  bit_val= 0
42=> 0uS  bit_val= 0
43=> 0uS  bit_val= 0
44=> 0uS  bit_val= 0
45=> 0uS  bit_val= 0
46=> 0uS  bit_val= 0
47=> 0uS  bit_val= 0
48=> 0uS  bit_val= 0
49=> 0uS  bit_val= 0
50=> 0uS  bit_val= 0
51=> 0uS  bit_val= 0
52=> 0uS  bit_val= 0
53=> 0uS  bit_val= 0
54=> 0uS  bit_val= 0
55=> 0uS  bit_val= 0
56=> 0uS  bit_val= 0
57=> 0uS  bit_val= 0
58=> 0uS  bit_val= 0
59=> 0uS  bit_val= 0
60=> 0uS  bit_val= 0
61=> 0uS  bit_val= 0
62=> 0uS  bit_val= 0
63=> 0uS  bit_val= 0
64=> 0uS  bit_val= 0
65=> 0uS  bit_val= 0
66=> 0uS  bit_val= 0
67=> 0uS  bit_val= 0
68=> 0uS  bit_val= 0
69=> 0uS  bit_val= 0
70=> 0uS  bit_val= 0
71=> 0uS  bit_val= 0
72=> 0uS  bit_val= 0
73=> 0uS  bit_val= 0
74=> 0uS  bit_val= 0
75=> 0uS  bit_val= 0
76=> 0uS  bit_val= 0
77=> 0uS  bit_val= 0
78=> 0uS  bit_val= 0
79=> 0uS  bit_val= 0
80=> 0uS  bit_val= 0
* * * END * * *

...remember that I use a 4Mhz crystal so the pulse width is returned in 10us increments.

Acoording to the above dubugging infos we can see a 50uS pulse wich according to datasheet is the pulse before each "0" or "1" pulse!

One weird thing is also tha after pulse number 27 I read no pulses!!

[Demon]

Did you use 100nF capacitor as mentionned in DHT22 datasheet?

Edit: there's a guy here that gets only 21 elements, sounds like a similar issue:
http://www.picaxeforum.co.uk/showthr...22-Please-Help

Edit 2: this is in C, but read the blog at top. Has several interesting comments.
http://blog.ringerc.id.au/2012/01/us...ht-22.html?m=1

Can you run faster than 4mhz? Can you use internal osc instead? 18F generally can go quite fast.

Robert

[bitmaniac]

Thanks for trying to help my problem out my friend!

Yes, I tried with 100nf on power.

I am searching over the net for a week now and came across 2 different datasheet of the same sensor...DHT22 and sites with code in C e.t.c I have read most of them and trying to use picbasic instead!

I will examine carefully your links (VERY good infos!!!) and come back....

[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