What I want to do
I want to create a platform with the capacity to control a large number of sensors and actuators necessary for the hydronponics system outlined in this wiki, and to serve as the central gateway to a cloud-enabled dashboard. The basis for this experiment is the new Arduino Yun which combines an OpenWRT/Linux wifi processor with an Arduino Leonardo Microcontroller. However, the complexity of the Open Source Hydroponics Platform is such that it will likely require multiple microcontrollers to adequately handle the tasks involved.
The new ATmega32u4 Microcontroller chip utilized by the Arduino Yun/Leonardo etc... has proven to be a popular platform for dedicated platforms like the Visualight (discussed on these forums) and the LeoPhi Ph Sensor.
My concept would retain the same basic structure utilized by the Arduino Yun, only instead of being limited to one microcontroller, it will allow 3 or 4 connections simultaneously.
The Yun is based on the Atheros AR 9331 System-on-a-Chip (SOC). The same chip drives the TP-Link WR703n travel router, which when flashed with a custom OpenWRT firmware has been beloved by hackers as a cheap means of adding wifi to arduino projects. As a consumer product howevr, TL-WR703n is not optimized for additional inputs and outputs and lacks sufficient memory for anything close to the tasks we'd need it for, so a dedicated development board is needed for the AR 9331. Luckily, this board exists in the form of the _Dragino_. The Dragino is basically an OpenWRT router with ample I/O ports to make it more hacker friendly.
While my experience with similar products has been hit or miss in the past, the Dragino developers have done a fantastic job keeping up-to-date documentation and software upgrades. In fact, they've not only gone through all the work porting the Arduino Yun firmware to their board, but they even give you the option to ship with the Yun firmware included by default!
. Setting it up was surprisingly straightforward following the step-by-step walk though on the Dragino Wiki. Once an Arduino Leonardo has been connected through the UART, it can be programmed just as if it were a Yun.
My attempt and results
I connected the Leonardo to Dragino following the image below, and it worked as advertised.
Questions and next steps
The next step will be to connect the Arduino Micro as its also based on an ATmega32u4 and has a much smaller footprint. Next, I will try connecting purpose-built boards like the Visualight to see if anything more needs to be modified. The final test will be to see if the Dragino can indeed control 2 or more Leonardos simultaneously.
Why I'm interested
See Project Wiki at http://publiclab.org/wiki/new-concepts-for-oshw-in-indoor-gardening full a full overview of the Hydroponics project.
Pinoccio is an open source / open hardware solution that makes data collection a breeze. It runs on Arduino and makes everyone's life considerably easier.
I'm unsure how well their interface supports actuators. Since it is open source and open hardware and super pretty, it might be something to look into modifying rather than rolling your own.
 link: http://pinocc.io/
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