DS18B20

[tolyan249]

How can you find out whether the DS18B20 sensor is connected or not, since it might break or the wires might come loose, and so on?

Thank you.

[trastikata]

Check the serial number.

[Pepe]

Add this to Les's program.

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'                                  Let's find out together what makes a PIC Tick!
'
' Read a DS18B20 temperature sensor with a 12-bit resolution
' And display the temperature in Celsius on a serial terminal
' This version uses integers only for the calculations, but still gives a 0.1 degree temperature resolution.
'
' Written for the Positron8 compiler by Les Johnson.
'
    Device = 18F26K22                                      ' Tell the compiler what device to compile for
    Declare Xtal = 64                                      ' Tell the compiler what frequency the device is operating at
'
' Setup USART1
'
    Declare Hserial1_Baud = 9600                            ' Setup the Baud rate of USART1
    Declare HRSOut1_Pin = PORTC.6                          ' Setup the pin used for USART1 TX

    Symbol DQ_Pin = PORTC.0                                ' Set the data pin (DQ) for the DS18B20 device
'
' Create a variable for the demo
'
    Dim wTemperature As SWord                              ' Holds the temperature returned from the DS18B20_Read procedure

'------------------------------------------------------------------
' The main program starts here
' Read a DS18B20 device and transmit the temperature in Celsius to a serial terminal
'
Main:
    Internal_Osc_64MHz()                                        ' Set the internal oscillator to operate at 64MHz

    Do                                                          ' Create a loop
        wTemperature = DS18B20_Read()                          ' Read the temperature from the DS18B20 device
        If wTemperature <> 32767 Then                          ' Was the temperature read?
            HRSOutLn "Temperature = ", SDec wTemperature / 10,  ' \
                    ".", SDec wTemperature // 10, " C"        ' / Yes. So transmit the temperature value to a serial terminal
                                  Else
            HRSOutln "Sensor error"
        EndIf
    Loop                                                        ' Do it forever

'-------------------------------------------------------------------
' Read a DS18B20 device with its default 12-bit resolution
' Input    : None
' Output    : Returns the integer temperature value x10, in Celsius
'          : If the device cannot be read, the value returned is 32767
' Notes    : Uses integer calculations, so the temperature returned will need to be divided
'            for the whole and fraction numbers to be displayed
'          : Because the CRC value is not being used from the DS18B20 device,
'            there is no need to read all 9 data bytes from it
'
Proc DS18B20_Read(), SWord
    Dim bTimeOut As Result.Byte0  = $FF                    ' A timeout for the conversion wait loop
    OWrite DQ_Pin, 1, [$CC, $44]                            ' Start a temperature conversion
'
' Wait until the conversion is complete
'
    Repeat                                                  ' Create a loop
        If ORead DQ_Pin, 4 = 1 Then ReadTemp                ' Exit the loop if the conversion is complete
        DelayMS 10                                          ' A small delay within the loop
        Dec bTimeOut                                        ' Decrement the timeout counter
    Until STATUSbits_Z = 1                                  ' Finish the loop when it reaches zero
    Result = 32767                                          ' Return 32767 because the loop completed
    ExitProc                                                ' Exit the procedure prematurely because it timed out
ReadTemp:
    OWrite DQ_Pin, 1, [$CC, $BE]                            ' Set to read the temperature
    ORead DQ_Pin, 0, [Result.Byte0, Result.Byte1]          ' Read the temperature data only from the DS18B20 device
    Result = Result * 10                                    ' Multiply the raw temperature value by 10
    Result = Result / 16                                    ' Convert to Celsius
EndProc

'------------------------------------------------------------------
' Set the PIC18F26K22's internal oscillator to operate at 64MHz
' Input    : None
' Output    : None
' Notes    : Waits for the internal oscillator to become stable
'
Proc Internal_Osc_64MHz()
    OSCCON  = %01110000
    OSCCON2 = %10000100
    Repeat : Until OSCCONbits_HFIOFS = 1        ' Keep looping until the oscillator is stable
    Set OSCTUNEbits_PLLEN                      ' Enable the 4xPLL
EndProc

'------------------------------------------------------------------
' Setup the configuration fuses for 64MHz operation using the internal oscillator for a PIC18F26K22 device
'
Config_Start
    FOSC = INTIO67      ' Internal oscillator block. Port function on RA6 and RA7
    PLLCFG = On        ' Oscillator not multiplied by 4
    PRICLKEN = Off      ' Primary clock disabled
    IESO = Off          ' Oscillator Switchover mode disabled
    Debug = Off        ' Background debugger disabled. RB6 and RB7 Configured as general purpose I/O pins
    WDTEN = Off        ' WDT disabled (Control is placed on SWDTEN bit)
    XINST = Off        ' Standard mnemonic mode enabled
    FCMEN = On          ' Fail-Safe Clock Monitor enabled
    PWRTEN = On        ' PWRT enabled
    BOREN = On          ' Brown-out Reset enabled and Controlled by software (SBOREN is enabled)
    BORV = 190          ' VBOR set to 1.9 V nominal
    WDTPS = 128        ' Watchdog prescaler set to 1:128
    MCLRE = EXTMCLR    ' MCLR pin enabled, RE3 input pin disabled
    HFOFST = Off        ' The system clock is held Off until the HF-INTOSC is stable.
    PBADEN = Off        ' PORTB<4:0> pins are Configured as digital I/O on Reset
    CCP2MX = PORTC1    ' CCP2 input/output is multiplexed with RC1
    CCP3MX = PORTB5    ' P3A/CCP3 input/output is multiplexed with RB5
    T3CMX = PORTC0      ' T3CKI is on RC0
    P2BMX = PORTB5      ' P2B is on RB5
    STVREN = On        ' Stack full/underflow will cause Reset
    LVP = Off          ' Single-Supply ICSP disabled
    Cp0 = Off          ' Block 0 ($000800 - $001FFF) not code-protected
    CP1 = Off          ' Block 1 ($002000 - $003FFF) not code-protected
    CPB = Off          ' Boot block ($000000 - $0007FF) not code-protected
    CPD = Off          ' Data EEPROM not code-protected
    WRT0 = Off          ' Block 0 ($000800 - $001FFF) not write-protected
    WRT1 = Off          ' Block 1 ($002000 - $003FFF) not write-protected
    WRTB = Off          ' Boot block ($000000 - $0007FF) not write-protected
    WRTC = Off          ' Configuration registers ($300000 - $3000FF) not write-protected
    WRTD = Off          ' Data EEPROM not write-protected
    EBTR0 = Off        ' Block 0 ($000800 - $001FFF) not protected from table reads executed in other blocks
    EBTR1 = Off        ' Block 1 ($002000 - $003FFF) not protected from table reads executed in other blocks
    EBTRB = Off        ' Boot block ($000000 - $0007FF) not protected from table reads executed in other blocks
Config_End


[tolyan249]

If ORead DQ_Pin, 4 = 1 Then
 flagds=1
 else
 flagds=0
 endif

Thank you, this works: 0 — there is a sensor, 1 — there is no sensor.



Thanks for the help