'######################## DHT-22 Humidity & Temperatur Sensor ##################
' DHT-22
'
' |-----o-- Vcc
' | |
' | -
' | 10k
' | -
' | |
' |-----o-- Data ~~~ PC0 (µC)
' |
' |-------- NC
' |
' |-------- GND
'
' Timings: Bit = 0 ~ 28 µs / Bit = 1 ~ 70 µs
' Min_time = 28 µs < TCNT0 Value (ticks) < 70 µs (in ticks)
' every time > Min_time >>> Bit = 1
' every time < Min_time >>> Bit = 0
'
' Min_time ~ 20 (ticks) for 3.6864 MHz
'
' ~ ticks for Bit = 0: 26 µs * $crystal (in MHz) / Prescale
' ~ ticks for Bit = 1: 70 µs * $crystal (in MHz) / Prescale
'
'######################## DHT-22 Humidity & Temperature Sensor##################
$regfile = "m168def.dat"
$crystal = 16000000
$baud = 115200
$hwstack = 64
$swstack = 64
$framesize = 64
'#####################################
Config Pind.4 = Input
Config Timer0 = Timer , Prescale = 8
'#####################################
Const Min_time = 95 'Wert je nach Quarzfrequenz anpassen (siehe ticks)
Dim Count As Byte
Dim Signaltime(43) As Byte
Dim Humidityw As Word
Dim Temperaturew As Word
Dim Humsens_chksum As Byte
Dim Humiditys As String * 16
Dim Temperatures As String * 16
Dim Strstring As String * 14
Dim Ib As Byte
'-------------------------------------------------------------------------------
'Definieren der LCD-Pins inkl. SPI
'
Config Portc.2 = Output
Lcdndc Alias Portc.2
Config Portc.1 = Output
Lcdnce Alias Portc.1
Config Portc.0 = Output
Lcdnre Alias Portc.0
Config Portc.5 = Output
Lcdnbl Alias Portc.5
'Konfiguriern SPI in Soft-Mode
Config Spi = Soft , Dout = Portc.3 , Ss = None , Clock = Portc.4
'Initialise Spi
Spiinit
'-------------------------------------------------------------------------------
'###############################################################################
Declare Sub Read_timings
Declare Sub Humtemp_values
Declare Function Compare_chksum(byval Hsens_humidity As Word , Byval Hsens_temperature As Word , Byval Hsens_chksum As Byte) As Byte
'###############################################################################
' Haupt-Programm
$include "lcdn_init.inc"
'Initialisiern des Nokia-LCD's
Lcdn_reset
Lcdn_init
Lcdn_clear
'Startsequez: Backlight blinkt 3x
'For Ib = 1 To 3
' Toggle Lcdnbl
' Waitms 500
'Next Ib
Set Lcdnbl
Lcdn_position 0 , 0
Lcdn_print "Test DHT22 mit"
Lcdn_position 0 , 1
Lcdn_print "ATmega168"
Do
Call Humtemp_values
If Compare_chksum(humidityw , Temperaturew , Humsens_chksum) = 1 Then
Humiditys = Str(humidityw)
Temperatures = Str(temperaturew)
Strstring = "Humi: " + Format(humiditys , "0.0")
'Strstring = Humiditys
Lcdn_position 0 , 3
Lcdn_print Strstring
Strstring = "Temp: " + Format(temperatures , "0.0")
'Strstring = Temperatures
Lcdn_position 0 , 4
Lcdn_print Strstring
Else
Strstring = "DHT Read-Error"
Lcdn_position 0 , 5
Lcdn_print Strstring
End If
Wait 3
Loop
End
'###############################################################################
' Read timings
' measure time (in ticks) for signal = high (Start / Stop TIMER0)
' 1st two measurements do not contain sensor values
Sub Read_timings
Count = 1
Config Pind.4 = Output : Portd.4 = 0 ' request data
Waitms 20 ' wait 20 ms
Config Pind.4 = Input ' wait for data, receive data
While Count < 43 'collect 42 timings / signals
Bitwait Pind.4 , Set 'signal goes high > start timer
Start Timer0
Bitwait Pind.4 , Reset 'signal goes low > stop timer
Stop Timer0
Signaltime(count) = Tcnt0 'store number of ticks per signal in Signaltime byte
Tcnt0 = 0
Incr Count
Wend
End Sub
'###############################################################################
'Humidity and temperature values
' transform timings into bits (40 timings > 40 Bits)
' every time (in ticks) > Min_time >>> Bit = 1
' every time (in ticks) < Min_time >>> Bit = 0
' first word contains humidity
' second word contains temperature
' last byte contains checksum
Sub Humtemp_values
Local X As Byte
Humidityw = 0
Temperaturew = 0
Humsens_chksum = 0
Call Read_timings
For Count = 3 To 42 ' Erste zwei Bits überspringen
Select Case Count
Case 3 To 18
X = 18 - Count
If Signaltime(count) > Min_time Then Toggle Humidityw.x
Case 19 To 34
X = 34 - Count
If Signaltime(count) > Min_time Then Toggle Temperaturew.x
Case 34 To 42
X = 42 - Count
If Signaltime(count) > Min_time Then Toggle Humsens_chksum.x
End Select
Next
End Sub
'###############################################################################
' Calculate Checksum and compare with trasnmitted value
Function Compare_chksum(byval Hsens_humidity As Word , Byval Hsens_temperature As Word , Byval Hsens_chksum As Byte) As Byte
Local Chksum As Byte
Chksum = Low(hsens_humidity ) + High(hsens_humidity )
Chksum = Chksum + Low(hsens_temperature)
Chksum = Chksum + High(hsens_temperature)
If Chksum = Hsens_chksum Then
Compare_chksum = 1
Else
Compare_chksum = 0
End If
End Function
$include "lcdn_sub.inc"
:bye
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