Reading DS18B20 via DS2482-800

  • Schmittlich

    Schmittlich - 2019-02-05

    Hello, I am mew with CODESYS
    But I do have experience with TwinCAT 2

    I want to read temperature from 8x DS2482 via I2C.
    On one port of DS2482-800 only one DS18B20 - so they can be replaced without changing the ID of the DS18B20.
    Therfore I want to create a simple Library for the DS2482-800

    With a MICROCHIP-PIC I can already read the DS18B20.
    Now I want to do the same with CODESYS on the Raspberry 3

    Can anyone assist me, in this project?
    As a first step, I would be happy to create some Functions to acces the DS2482.
    But right now, I have proplems to use the low-level comands like write8 or read8 I2C-comands inside a regular Function block.

    Lets start with the first step ... sending a reset to the DS2482

    This is, how I dit it with my PIC16F887:
    ' Returns: TRUE if device was reset
    ' FALSE device not detected or failure to perform reset
    Function ds2482_reset() As Bit
    Dim xstatus As Byte
    Dim acknowledge As Bit
    ds2482_reset = False
    '// device reset
    I2CWrite1 sda, scl, i2c_addressw, cmd_drst
    WaitUs 10
    I2CRead1 sda, scl, i2c_addressr, xstatus
    '// check For failure due To incorrect Read back of STATUS
    xstatus = xstatus And 0xf7
    If xstatus = 0x10 Then ds2482_reset = True
    End Function

  • Schmittlich

    Schmittlich - 2019-02-06

    OK, in meantime I found the first important trick how to use the "low-level" comands.
    Add I2C-Master and then use following syntax inside the program:

    byWrite:=i2c_master.write(16#20, ADR(byOut), 1); //Using a PCF8574, ADR(byIn), 1); //Using a PCF8574

  • Ingo

    Ingo - 2019-02-08

    Nice that you found it already. If you like to turn your library into a real I/O driver afterwards, please take a look at

    Have fun, and if you have further questions regarding generic I/O stuff feel free to ask.

    And if you like to share your work, is a good place for that.

    Gesendet von meinem LG-H870 mit Tapatalk


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