Updated to work on all revisions (Rev1, Rev2, B+ and above)

[Aichan]

Removed RaspberryPinNumber as it was confusing (to me) feel free to add it again.

BroadcomPinNumber is now "private" as you could not write portable code with it + numbering was confusing (0,1,21 became 2,3,27 after Rev1)

PhysicalPinNumber now abstracts BroadcomPinNumber detecting the Raspberry Pi revision type

[andycb]

Thanks for this. Some (minor and hopefully constructive) feedback:

• I think you're right to remove RaspberryPinNumber, I seem to remember when I first made this, there were several ways to addressing the Pin numbers, but I don’t see anybody using this system anymore, nor can I find a pin out diagram with them on.

• Your method of detecting the Pi revision will not work with Windows. OSx or non Linux systems. Please can you add a safe default if the code is in Test mode, running on a non-Lunix platform and if the detection fails on a non-pi Linux install?

• Was it necessary to wrap BroadcomPinNumber in a PartalClass of LibGpio? Given that LibGpio is always consumed as a separate assembly, would making BroadcomPinNumber internal not have been a cleaner way of removing it from the public interface?

• Unfortunately, this breaks a lot of the documentation and the demos, but I don't think that's a huge concern right now.

• Ideally GpioLayout.cs would have a copyright header similar to….

  //-----------------------------------------------------------------------
  //
  // Copyright (C) 2015 Andrew Bradford and contributors - see https://github.com/andycb/PiSharp/graphs/contributors
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
  // associated documentation files (the "Software"), to deal in the Software without restriction,
  // including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
  // and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject
  // to the following conditions:
  //
  // The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
  // WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
  // COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  // ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  //
  //-----------------------------------------------------------------------