Maxim DS2482 Support

[Anobium]

I have posted a new device driver for the Maxim DS2482 device. The DS2482 is an I²C to 1-Wire bridge. The DS2482 allows any host with I²C communication to generate properly timed and slew-controlled 1-Wire waveforms. This new driver provides detailed communication sessions for common 1-Wire master operations. I have used the DS18B20 sensor in this example.

The is based on the Maxim application note 3684 and therefore supports all the 1-Wire functions, called primitives, which an application must have to perform any 1-Wire communication session.

The driver has all the primitives required for normal operation.

• The function OWReset resets all the 1-Wire slaves on the network, readying them for a command from the 1-Wire master.
• The function OWWriteBit writes a bit from the 1-Wire master to the slaves, and the function OWReadBit reads a bit from the 1-Wire slaves. Since the 1-Wire master must start all 1-Wire bit communication, a "read" is technically a "write" of a single bit with the result sampled. Almost all other 1-Wire operations can be constructed from these three operations. For example, a byte written to the 1-Wire network is just eight single bit writes.
• A 1-Wire Search Algorithm can also be constructed using these same three primitives. However, the DS2482 incorporates a search helper function called the 1-Wire triplet, which greatly reduces the communication overhead required for a search. Similarly there is a byte 1-Wire communication command that is more efficient than doing eight single-bit commands.

Anobium

See https://sourceforge.net/p/gcbasic/code/HEAD/tree/GCBASIC/trunk/include/ds2482.h

'Sample Code a DS18B20 - requires #include <ds2482.h>

 ' Required to DS18B20 support
  #define   ConvertT 68                     ' 0x44 (68).  DS18B20 command set
  #define   ReadScratch 190                     ' 0xBE (190).  DS18B20 command set
  Dim DSdata As Word                          ' required for negative numbers support
  Dim TempC_100 as word                       ' variable to handle the temperature calculations

      Locate 0,0
      Print "DS2428        "

      if ds2482_detect = true then
         HSerPrint "DS2482 Device"
      Else
         if ds2482_reset = true then
            HSerPrint "I2C Bus Error, or"
            HSerPrintCRLF
            HSerPrint "One Wire Device(s)Missing"
         else
            HSerPrint "DS2482 Missing"
         end if
         exit sub
      end if

      ' read DS18B20 64-BIT LASERED ROM CODE
      if ds2482_OWReset = true then
            DSdata = 0
            oneWire_writeByte ( READ_DEVICE_ROM )       ' Send 64-BIT LASERED ROM CODE read command

            for cc = 0 to 7
                oneWire_ReadByte ( DSdata )             ' Process and display the 64-BIT LASERED ROM CODE
                HSerPrint hex(DSdata)
            next

      end if

      Locate 1,0

      ' read DS18B20 device on the bus. Using the DS18B20 protocol. See the device Datasheet.
      if ds2482_OWReset = true then
        DSdata = 0
        oneWire_writeByte ( SKIP_ROM )
        oneWire_writeByte ( ConvertT )
        ds2482_temp = ds2482_OWReset
        oneWire_writeByte ( SKIP_ROM )
        oneWire_writeByte ( ReadScratch )
        ' read temperature values
        oneWire_ReadByte ( DSdata )    ' we now have one byte of the 12 bit number
        oneWire_ReadByte ( DSdata_h )    ' we now have other byte of the 12 bit number

        ' do some simple maths to calculate the temp.
        SignBit = DSdata / 256 / 128
        If SignBit = 0 Then goto Positive
        ' its negative!
        DSdata = ( DSdata # 0xffff ) + 1 ' take twos comp

Positive:
         ' Convert value * 0.0625. Mulitple value by 6 then add result to multiplication of the value with 25 then divide result by 100.
         TempC_100 =  DSdata * 6        
         DSdata = ( DSdata * 25 ) / 100
         TempC_100 = TempC_100 + DSdata

         Whole = TempC_100 / 100
         Fract = TempC_100 % 100
         If SignBit = 0 Then goto DisplayTemp
         HSerPrint "-"

DisplayTemp:
         HSerPrint  str(Whole)
         HSerPrint  "."

    ' To ensure the decimal part is two digits
     Dig = Fract / 10
     HSerPrint Dig
     Dig = Fract % 10
     HSerPrint Dig:
     HSerPrint  "c"
  else
    HSerPrint  "Error one One Wire Bus"
  end if