$regfile = "M8def.dat"
$crystal = 3686400
$baud = 9600
$lib "i2c_twi.lbx"

Dim B1 As Byte
Dim B2 As Byte
Dim B3 As Byte
Dim B4 As Byte
Dim X As String * 10
Dim Y As Integer
Dim Z As Byte

Dim Ctr As Byte
Dim Dataword As Word
Dim Command As Byte
Dim Dis As String * 20

Dim Calc As Single
Dim Calc2 As Single
Dim Rhlinear As Single
Dim Rhlintemp As Single
Dim Tempc As Single
Dim Tempf As Single

Const C1 = -4
Const C2 = 0.0405
Const C3 = -0.0000028
Const T1c = .01
Const T2 = .00008
Const T1f = .018
Y = 0
Z = 0

Declare Sub Getit()

Config Timer1 = Timer , Prescale = 256
On Timer1 On_timer1
Enable Timer1
Enable Interrupts
Timer1 = 51135


Do

   If Z = 3 Then
      Sck Alias Portc.5
      Dataout Alias Portc.4
      Datain Alias Pinc.4

      Ddrc = &B11111111
      Config Pinc.5 = Output
      Config Pinc.4 = Output

      Set Dataout
      For Ctr = 1 To 12
             Set Sck
             Waitus 2
             Reset Sck
             Waitus 2
      Next Ctr

     Command = &B00000011
     Call Getit

     Tempf = T1f * Dataword
     Tempf = Tempf - 39.35

     Tempc = T1c * Dataword
     Tempc = Tempc - 39.66

     Dis = Fusing(tempc , "###.##")
     Print "Temperatur = " ; Dis ; " (C)"

     Command = &B00000101
     Call Getit
     Calc = C2 * Dataword
     Calc2 = Dataword * Dataword
     Calc2 = C3 * Calc2
     Calc = Calc + C1
     Rhlinear = Calc + Calc2


     Calc = T2 * Dataword
     Calc = Calc + T1c
     Calc2 = Tempc - 25
     Calc = Calc2 * Calc
     Rhlintemp = Calc + Rhlinear

     Dis = Fusing(rhlintemp , "##.##")
     Print "relative Feuchte  = " ; Dis ; " (rF%)" ;

     Z = 4
   End If

   If Z = 7 Then
   Gosub Co2messen
   Z = 0
   End If

Loop


On_timer1:
   Z = Z + 1
   Timer1 = 51135
Return


Co2messen:
   I2cinit
   Config Twi = 50000
   Config Scl = Portc.5
   Config Sda = Portc.4

  I2cstart                                                  ' Send start sequence: Fallende SDA-Flanke wenn SCL high
  I2cwbyte &HD0                                             ' Adresse 0x68 mit R/W low = HD0. Read/Write bit0 encoding Read = 1, Write = 0.
  I2cwbyte &H22                                             ' command read ram and number of databytes
  I2cwbyte &H00                                             ' ram address (for command register?)
  I2cwbyte &H08                                             ' ram address
  I2cwbyte &H2A                                             ' Checksum is calculated as sum of byte 2, 3 and 4.
  Print
  I2cstop

  Waitus 350

  I2cstart                                                  ' restart
    I2cwbyte &HD1                                           ' senden der Slaveadresse mit R/W bit0 = 1
  I2crbyte B1 , Ack                                         ' Slave sendet Byte: operation status, where bit 0 tells us if the read command was successfully executed.
  I2crbyte B2 , Ack                                         ' CO2 value high byte
  I2crbyte B3 , Ack                                         ' CO2 value low byte
  I2crbyte B4 , Nack                                        ' beinhaltet checksum
  I2cstop                                                   ' Steigende SDA-Flanke wenn SCL low

  Waitus 350

  X = Hex(b2)
  X = X + Hex(b3)
  Y = Hexval(x)

  Print "CO2-Wert: "; Y ; " (ppm)" ;
  Y = 0
Return


Sub Getit()
   Local Datavalue As Word
   Local Databyte As Byte


   Set Sck
   Reset Dataout
   Reset Sck
   Set Sck
   Set Dataout
   Reset Sck


   Shiftout Dataout , Sck , Command , 1

   Ddrc = &B11101111
   Config Pinc.4 = Input
   Set Sck
   Reset Sck
   Waitus 10
   Bitwait Pinc.4 , Reset

   Shiftin Datain , Sck , Databyte , 1
   Datavalue = Databyte

   Ddrc = &B11111111
   Config Pinc.4 = Output

   Reset Dataout
   Set Sck
   Reset Sck

   Ddrc = &B11101111
   Config Pinc.4 = Input

   Shiftin Datain , Sck , Databyte , 1
   Shift Datavalue , Left , 8
   Datavalue = Datavalue Or Databyte

   Dataword = Datavalue

   Ddrc = &B11111111
   Config Pinc.4 = Output

   Reset Dataout
   Set Sck
   Reset Sck

   Ddrc = &B11101111
   Config Pinc.4 = Input

   Shiftin Datain , Sck , Databyte , 1


   Ddrc = &B11111111
   Config Pinc.4 = Output

   Set Dataout
   Set Sck
   Reset Sck
End Sub
Return

End