Add support for Arduino Zero

[soundanalogous]

You will need an official Arduino Pro Zero board. Do not get an M0 Pro board, that will not work with Firmata.

In order to use, you'll have to make sure the Servo library is at least version 1.1.0. Follow these instructions:

1. In the Arduino IDE (the arduino.cc one), go to Sketch > Include libraries > Manage libraries.
2. Search for "Servo" and scroll down the results list to "Servo by Michael Margolis..."
3. Tap on the list item (I wish this was more clear in the UI), then an option to Update will appear
4. Click on update.

TODO:

• Ensure only digital I/O pins are reset in systemResetCallback
• Thorough testing

[soundanalogous]

This is going to push out the v2.5 release at least a week while I wait for my Zero board to arrive.

[rwaldron]

Can you link to the Zero you ordered? I don't want to order the wrong thing again.

[soundanalogous]

I ordered direct from arduino.cc: http://store-usa.arduino.cc/products/abx00003

[soundanalogous]

Zero does not seem to be very stable yet. I'm seeing strange issues like digital input pins no longer working when a digital output pin is toggled on the same port. Need to do more experimentation outside of Firmata to better understand the root of the issues.

[soundanalogous]

Zero does not like this: https://github.com/firmata/arduino/blob/master/examples/StandardFirmata/StandardFirmata.ino#L266. Commenting out that line will enable digital input. However it still does not solve all problems I'm seeing.

[soundanalogous]

Issue with Zero per previous comment is describe here: #231

[soundanalogous]

Turns out for Zero, internal pull-ups can only be set by setting the pinMode to INPUT_PULLUP so the last commit does not help the Zero situation since writing HIGH to an input pin will not enable internal pull ups on Zero (but will for all non SAMD boards).

[soundanalogous]

Fixed internal pull-up issue in last commit.