Dht11 - 16f877a

[bitmaniac]

@Thanasis ...if you want to keep 20Mhz try to change

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'

to this one

if pulse(x)>=9 and pulse(x)<=21 then p(x)=0 'if pulsewidth between 20 and 40uS then read as '0'
if pulse(x)>=29 and pulse(x)<=41 then p(x)=1 'if pulsewidth between 60 and 80uS then read as '1'

and let me know

[Scampy]

@

and let me know

OK an old post I know, but I received a DHT11 today and had a play. This works fine on an 18F2520 running with a 20mhz crystal.

ASM 
  __CONFIG    _CONFIG1H, _OSC_HS_1H
  __CONFIG    _CONFIG2L, _PWRT_ON_2L  
  __CONFIG    _CONFIG2H, _WDT_ON_2H & _WDTPS_512_2H
  __CONFIG    _CONFIG3H, _MCLRE_ON_3H & _LPT1OSC_OFF_3H & _PBADEN_OFF_3H  
  __CONFIG    _CONFIG4L, _LVP_OFF_4L & _XINST_OFF_4L
ENDASM


'*******************************************************************************
' LCD (20 x 4) set up
'*******************************************************************************

DEFINE LCD_DREG  PORTB                  ' LCD Data port
DEFINE LCD_DBIT  0                      ' starting Data bit (0 or 4)
DEFINE LCD_EREG  PORTB                  ' LCD Enable port
DEFINE LCD_EBIT  5                      '     Enable bit  (on EasyPIC 5 LCD)
DEFINE LCD_RSREG PORTB                  ' LCD Register Select port
DEFINE LCD_RSBIT 4                      '     Register Select bit   (on EasyPIC 5 LCD)
DEFINE LCD_BITS  4                      ' LCD bus size (4 or 8 bits)
DEFINE LCD_LINES 4                      ' number of lines on LCD
DEFINE LCD_COMMANDUS 2000               ' Command delay time in us 
DEFINE LCD_DATAUS 50                    ' Data delay time in us 

'*******************************************************************************
' Defines Statements
'*******************************************************************************

DEFINE  OSC 20                          ' 18F4520 / 18F2520, 20mhz crystal
ADCON1 = $0F
clear    

'*******************************************************************************
'Analog and Comparator settings
'*******************************************************************************

ADCON0 = %00000000                      'AD converter module disabled
ADCON1 = %00001111                      'All Digital
ADCON2 = %00000000
CMCON = 7                               'Disable Comparators

'*******************************************************************************
'Port and Register settings  (interrupts)
'*******************************************************************************
    
TRISA  = %00010111              
TRISB  = %00000011               
T0CON  = %11000111

T1CON = %00000001                               ; free-running, 1:1 prescaler
TMR1H = %11111111
TMR1L = %11111011


'*******************************************************************************

LCDOUT $FE,1:FLAGS=0:PAUSE 250:LCDOUT $FE,1:PAUSE 250 ' Initialize LCD

'*******************************************************************************

dht var byte[32]
humidite var byte
haut var byte
bas var byte
temp var byte
x var byte
dht11 var portA.5

'*******************************************************************************
start:
TRISA.5 = 0 '
high dht11
pause 2000 ' wait 2 sec
low dht11 : pause 18' send 20ms low
high dht11 : pauseus 30 ' send 40us hi
TRISA.5 = 0
PulsIn PORTA.5, 1, haut
if haut < 15 then goto start
for x = 31 to 0 step-1
PulsIn PORTA.5, 1, dht[x] ' 1
next x
For x = 31 to 0 step-1
if dht(x)>=9 and dht(x)<=21 then dht(x)=0 'if pulsewidth between 20 and 40uS then read as '0'
if dht(x)>=29 and dht(x)<=41 then dht(x)=1 'if pulsewidth between 60 and 80uS then read as '1'
next x
humidite=dht[31]*128+dht[30]*64+dht[29]*32+dht[28]*16+dht[27]*8+dht[26]*4+dht[25]*2+dht[24]*1
temp=dht[15]*128+ dht[14]*64+dht[13]*32+dht[12]*16+dht[11]*8+dht[10]*4+dht[9]*2+dht[8]*1
lcdout  $FE,1 
lcdout  $FE,$C0,"Humidite = ",#humidite,"% "
lcdout  $FE,$80,"Temperature = ",#temp,$DF,"C"
goto start

I've used Port A, pin 5 as the data line as I used an EasyPIC5 development board, and has the readings displayed on an 4 x 20 LCD rather than serial out.