Communications

As the decision to make a hierarchical structure came about, the need to communicate between the controllers, and from the main controller to the house required some thought.

Dockside communications could be handled by wire as the distances weren't huge. However I would need a bus style communication otherwise I would simply recreate the issues that centralized channel faced (lots of IO pins and thick heavy cables) This discounted RS232 style communications, leaving me with RS422A or RS485A as a solution. I looked into this and decided that for the price of the driver chips, I could use a wireless link based on the NRF24L01 chip. This device is controlled via SPI and uses the 2.4GHz ISM band (same as WiFi) and handles all of the on air communications. The modules are available on ebay for a very comparable price directly from China. This meant that the on dock wiring was reduced to a single 12v power pair for each node further helping the cost factor due to reducing the amount of copper.

To manage the communications from the house to the main controller, I quickly discounted wired solutions due to the distance needing to be covered. Initially entertained the idea of a device plugged into a USB port that allowed the computer to talk directly via the NRF network, but shortly after that, I discovered the ESP8266 device and decided that I could put the house to dock communications on my WiFi network. The microcontroller I selected for the main controller had the necessary UART port available to make this a simple task.