SMBus Support

[Proclivis]

The SERCOM file does not support repeated start, therefore SMBus transactions are not possible in Wire.

Can someone explain how to compile the serial library and put it into play? I would be happy to try to add support for repeated start. Im working on Ubuntu, so it would be nice to compile with a gcc toolchain, etc.

I work on SMBus stuff a lot, so I don't need handholding on the protocol. When done, the LTC PMBus library will eventually release to the public for anyone to use. Today it only works on Uno, Mega, etc.

[legomanww]

I've made the modifications I believe are necessary to enable repeated starts.

Here's a link to my fork commit: Commit

And a scope shot of it in action:

Example Arduino sketch code to use it:

  Wire.beginTransmission(WM8805_ADDR);
  Wire.write(reg);
  byte error = Wire.endTransmission(false);
  error = Wire.requestFrom(WM8805_ADDR, 1);
  if (Wire.available())
  {
    value = Wire.read();
  }

I can submit a pull request if someone else wants to test and verify the changes.

[sandeepmistry]

@legomanww thanks for sharing your change!

I've pulled it into my branch and modified it to wait for a bus state of idle or owner. This removes the need to track the repeated start state. See the following commit: sandeepmistry@9ae6633

Would you be able to test my branch out and see what the scope shows before I submit a pull request?
https://github.com/sandeepmistry/ArduinoCore-samd/tree/wire-master-repeated-starts

[legomanww]

Looks OK, except it doesn't compile as-is. Line 71 on Wire.cpp still has a reference to repeatedStart.

[sandeepmistry]

@legomanww thanks for trying it out!

I've corrected and created pull request #66.