Firstly, a word of warning Serial uploads always go to memory slot 0 of your Oak - no matter what is in that slot. A factory Oak boots to 0 looking for the system firmware, so if you upload via serial, you essentially wipe the ability for your Oak to do natively do OTA updates and firmware updates. If you want to restore that ability, you'll need to use follow the instruction on how to restore your Oak to factory defaults.

In order to talk to the Oak over Serial, you may need two pieces of software installed (in addition to the Arduino IDE with appropriate Oak board support). The first is Python, and the second is the PySerial module for python. If you are using a Mac or Linux computer, is is very likely Python is already installed. If you are using Windows, then you will need to install it. In either case, you will also need to install the PySerial library to allow communication with the Oak.

To install Python on Windows, download the installer from http://www.python.org/getit/. You'll want the 2.xx version (2.7.11 at the time of writing) as due to some changes in the Python syntax, using Python 3 will result in error messages.

To make it so the Arduino IDE can find Python now that you have it installed, you'll need add the program folder to the system path. How you do this varies from version to version of windows, but you can usually find it by typing 'system environment' on later versions of Windows, or looking under System Properties in the Control Panel on earlier versions. It's probably best if you do a web search for something like 'how to add python to path' if you are unsure. You basically want to add the program folder containing Python to the system path, so that that any program can access python. The default install path for the 2.7.11 version was C:\Python27.

Regardless of your operating system, it is fairly likely you will need to install PySerial, which allows Python to access your computers serial ports. You can start by downloading it from https://pypi.python.org/pypi/pyserial. On Windows, you can download the windows install, for other operating systems you will need the source file (pyserial-3.0.1.tar.gz at the time of writing).

If you are using a Mac or Linux computer, then open a Terminal session, 'cd' to wherever you downloaded pyserial-3.0.1.tar.gz and then issue the following command to unpack the installation folder.

tar -xzf pyserial-3.0.1.tar.gz

Then “cd” into the pyserial-3.0.1 folder, then run the command:

sudo python setup.py install

You should then be configuring things!

To program your Oak over serial, you will want to connect the GND of your USB-Serial Adapter to the Oak's GND, RX to TX, TX to RX, and P2 to GND. You can then power the Oak via the on-board MicroUSB slot, or by providing appropriate power to the VIN or VCC pins.

Needs pic of an adapter here, and some more detailed explaination of pin connections

You will need to change your Upload settings in the Arduino IDE (under the Tools menu) from “Particle OTA” to “Serial (Expert Use Only - Requires Python)”, and make sure that the Port settings is set to the right serial port.

Screenshot?

When you upload your program to your Oak, you should see a message in the compile/upload log at the bottom of the Arduino IDE displaying the following message. If you scroll that view, you should see the percentage increasing as the program is being transferred to your Oak.

Connecting… Erasing flash… Writing at 0x00002000… (0 %) Writing at 0x00002400… (0 %) Writing at 0x00002800… (1 %)

It should also have a end message similar to the one shown below

Writing at 0x00041000… (99 %) Writing at 0x00041400… (100 %) Wrote 260096 bytes at 0x00002000 in 25.7 seconds (81.1 kbit/s)… Leaving…