AVR Microcontroller Projects

This project displays the temperature on an LCD display with an resolution of 0.06degrees. DS1820 is used for sensing the temperature. It can measure temperature range from -55deg to +125deg. But i take care of only the possitive temperature.

There are 3 switches to change the alarm temperature, the user can increment the Alarm temperature by pressing the UP button and they can decrease the Alarm temperature by pressing the Down button. The Enter button is used to store the Alarm temperature on the microcontroller EEPROM. So that the value retains even after power failure.

Circuit Diagram

Program

'-----------------------------------------------------------------------------------------
'copyright                : (c) 2008-2009, AVRprojects.info
'purpose                  : DS1820 / DS18S20 Temperature Indicator
'-----------------------------------------------------------------------------------------

$regfile = "m8515.dat"                                      ' specify the used micro
$crystal = 8000000                                          ' used crystal frequency


Declare Sub Read1820

Config 1wire = Portd.7
Config Lcd = 16 * 2
Config Lcdpin = Pin , Db4 = Porta.2 , Db5 = Porta.3 , Db6 = Porta.4 , Db7 = Porta.5 , E = Porta.1 , Rs = Porta.0

Upbtn Alias Pinb.5
Downbtn Alias Pinb.6
Enterbtn Alias Pinb.7
Alarm Alias Pinc.3
Config Upbtn = Input
Config Downbtn = Input
Config Enterbtn = Input
Config Portc = Output

'Temp variables
Dim Bd1 As Byte
Dim Bd2 As Byte
Dim Bd7 As Byte
Dim Bd8 As Byte
Dim Alrmtemp As Byte

Dim I As Byte , Tmp As Byte
Dim T As Integer , T1 As Integer
Dim Bd(9) As Byte                                           'Scratchpad 0-8 72 bits incl CRC, explanations for DS1820
'Sc(1)  'Temperature LSB
'Sc(2) 'Temperature MSB
'Sc(3) 'TH/user byte 1 also SRAM
'Sc(4) 'TL/user byte 2 also SRAM
'Sc(5) 'config  also SRAM x R1 R0 1 1 1 1 1 - the r1 r0 are config for resolution - write FF to byte for 12 bit - others dont care
'Sc(6) 'res
'Sc(7) 'res
'Sc(8) 'res
'Sc(9) '8 CRC

'DALLAS DS1820 ROM and scratchpad commands''''''''''''''''''''''''''1wwrite....
'&H 33 read rom - single sensor
'&H CC skip rom
'&H BE read scratchpad
'&H 44 convert T

' Main loop
Cls
Cursor Off
'Read the alarm temperature from EEPROM
Readeeprom Alrmtemp , 10
If Alrmtemp = &HFF Then Alrmtemp = 30
Do
   1wwrite &HCC : 1wwrite &H44                              ' start measure
   Waitms 400                                               ' wait for end of conversion
   Read1820
   Debounce Upbtn , 0 , Uppr , Sub
   Debounce Downbtn , 0 , Dwnpr , Sub
   Debounce Enterbtn , 0 , Alarmpr , Sub
   Waitms 300
   Debounce Upbtn , 0 , Uppr , Sub
   Debounce Downbtn , 0 , Dwnpr , Sub
   Debounce Enterbtn , 0 , Alarmpr , Sub
   Waitms 300
   Debounce Upbtn , 0 , Uppr , Sub
   Debounce Downbtn , 0 , Dwnpr , Sub
   Debounce Enterbtn , 0 , Alarmpr , Sub
   Waitms 300
Loop
End                                                         'end program


Uppr:
   If Alrmtemp < 98 Then
      Alrmtemp = Alrmtemp + 1
      Cls
      Lcd "Temp:" ; T1 ; "." ; T
      Lowerline
      Lcd "Alarm Temp:" ; Alrmtemp
   End If
   Return

Dwnpr:
   If Alrmtemp > 1 Then
      Alrmtemp = Alrmtemp - 1
      Cls
      Lcd "Temp:" ; T1 ; "." ; T
      Lowerline
      Lcd "Alarm Temp:" ; Alrmtemp
   End If
   Return

Alarmpr:
   Writeeeprom Alrmtemp , 10
   Cls
   Lcd "Data Stored..."
   Waitms 500
   Return

'Read the DS1820 by skipping the ROM checking, since we are using only 1 sensor
Sub Read1820                                                ' reads sensor ans calculate                                               ' T for 0.1 C
   1wreset                                                  ' reset the bus
   1wwrite &HCC                                             ' read internal RAM
   1wwrite &HBE                                             ' read 9 data bytest
   Bd(1) = 1wread(9)
   Bd1 = Bd(1)
   Bd2 = Bd(2)
   Bd7 = Bd(7)
   Bd8 = Bd(8)
                                               ' read bytes in array
   1wreset                                                  ' reset the bus
      Tmp = Bd1 And 1
      If Tmp = 1 Then Decr Bd1                              ' 0.1C precision
          T = Bd1
          T = T * 50
          T = T - 25
          T1 = Bd8 - Bd7
          T1 = T1 * 100
          T1 = T1 / Bd8
          T = T + T1
          T1 = T / 100                                      'store tens
          T = T Mod 100                                     'store decimal number
          Cls
          Lcd "Temp:" ; T1 ; "." ; T
          Lowerline
          Lcd "Alarm Temp:" ; Alrmtemp

          If Alrmtemp > T1 Then
              Portc = &B00000100
          Else
              Portc = &B00000000
          End If
End Sub

End