The Design Document

All through the requirements elicitation process I was mulling design ideas over in my head. I have scoured through the requirements for the other components of the Revolution system to understand exactly what our component needs to do and how it will integrate with the other components. I have also read most of the Atmel MEGA1280 microcontroller datasheet to understand the limitations and requirements of the environment we need to work in.

A few weeks ago I created a hand written version of the Control Flow required for the software running the small switch panel. I identified the needed functionality to meet our requirements and developed a few algorithms to handle the difficulties we faced working in a microcontroller environment, especially regarding timing and making sure we can blink lights at the correct rate and ensure a change has really occurred to any of the switches or sensors before responding to them. I developed a timing mechanism we can utilize for the entire system to handle all of our timing requirements and also developed the basic outline for handling all of the switch and sensor changes we need to respond to. I developed the data structures required for overall system functionality but admit these still need some refinement.

The most difficult part of this design is dealing with the limitations of the serial communication we have available in the Atmel MEGA1280 microcontroller. The serial port and USART only transmit or receive one character at a time. Kevin made it clear that all communications need to be non-blocking. It took me a little while but with Kevin's prodding and advice, research of other solutions that have been developed, studying the 1280 datasheet, and sheer determination I developed the design for the serial communication layer and the protocol layer of our network communications.

Last week, in order to make sure we had discussion material for our meeting with Kevin, I wrote the entire design document we have to date. It included Serial IO, Protocol, Main Loop, Switch, Light Sensor, Magneto Switch, and Reset modules. Last Friday I was aware, and Kevin reinforced that just thowing everything we needed down on paper was not enough and thr document needed refinement, the design needed better flexibility and detail, and we needed to be done by our meeting today.

David and I agreed that I would continue to work on the Serial IO and Protocol modules and he could take what I have developed (basic design and control flow) for the other components and refine the design.

Today, the Serial IO and Protocol modules are basically done. I have two minor changes to implement in the design and will have these done tomorrow. I will begin coding these modules and be ready to make sure everything else gets done so Vertical Power will meet its deadlines.