J2ME 1-wire Library

Java ME 1-wire library

I adapted my version from Maxim’s 1-wire Java library owapi_1_10 because I wanted to use some of the nifty functions in the library since they were already figured out – why reinvent the wheel?  I did have to “invent” one of the spokes of the wheel – there was no Java “adapter” class for the DS2482 I2C 1-wire bridge chip so I came up with one. I took part in the Oracle Java ME MOOC using the Raspberry Pi, and being pretty much of a Java newbie, I learned a lot from this course. There was a lesson for accessing I2C devices using the Pi and Java ME. Using the I2C_Device code in the course I came up with a “I2CBridgeAdapter” class.  I want to release the code on GitHub if anybody is interested.   (Just don’t laugh too hard about my Java coding skills.)  If you have suggestions I’d welcome them.

Each of the Container classes may need to be changed; the readDevice() method
needs to call OWreadByte/OWwriteByte instead of what they are doing now.
Some more changes I made to adapt the library to I2C:

I renamed the read and write functions to be more clear: I2CsendByte(), I2CwriteByte(), and I2CwriteBytes().

Since the 1-wire API code from Maxim was
pretty much based on the serial DS2480 device which uses the DSPortAdapter as a parent class, I made the I2CBridgeAdapter a subclass of the I2C_Device.

In OneWireContainer10:
readDevice(): For the life of me I can’t figure out why the developers at Dallas Semi chose to do this:

// read scratchpad command
buffer [0] = ( byte ) READ_SCRATCHPAD_COMMAND;

// now add the read bytes for data bytes and crc8
for (int i = 1; i < 10; i++)
buffer [i] = ( byte ) 0x0FF;

// send the block
adapter.dataBlock(buffer, 0, buffer.length);

Have no idea why they’re sending a READ_SCRATCHPAD_COMMAND and 9 bytes of 0xFF, so I took that out figuring it must have something to do with the serial port adapter, like the DS9490.

The below also is weird:

// see if crc is correct
if (CRC8.compute(buffer, 1, 9) == 0)
System.arraycopy(buffer, 1, data, 0, 8);
throw new OneWireIOException(“OneWireContainer10-Error reading CRC8 from device.”);

How the CRC8 could be 0, I’m not sure. I’ll have to investigate.

Since the DS2482 reads one byte at a time from the 1-wire bus, the Container classes needed to be modified to do this using a for-loop.