Nuts & Volts - February 2004

Personal Robotics

Learn About Microcontrollers

This does take a bit of getting used to, but it does work well once you get the hang of it. One potential drawback of this method is synchronization to other hardware that operates at a different (or even variable) period than the IsoPod. This has been overcome by adding data buffers to the serial lines, for instance. The buffer stores the data transparently in the background, and presents it to you when you ask for it. The one exception here is that the CANbus does not have a buffer like this in the classical sense, but it does receive eight bytes of data at a time. Since the implementation of the buffers, I have not been troubled by the synchronous nature of IsoMax.

This brings me to another point. IsoMax, currently at V0.6, is a language in flux. While I believe it is finished, it is not fully accessorized to the level that New Micros wants it to be. This means that improvements will happen and, in fact, have happened through the versions, but the net effect is always a better platform to work from.

Because the sheer volume of registers for hardware access is mind numbing at times, IsoMax incorporates very high-level object-oriented words. I like to call them template words. They are great for the beginner, and can help you get something up and running quickly, but some of them are notoriously slow. The reason for their slowness is that every time you use them, they have to "pave the way" for themselves. They make no assumptions; they configure each and every register that is required, each and every time they are called. I usually start out with them, and then if things show signs of slowing up, I go through and replace them with lower level code. They are also handy for seeing how registers get configured when you use them. This makes them ideal as a teaching tool.

Interestingly enough, IsoMax also provides words called trinaries for working with numbers at the bit level that are lightning fast. Trinaries allow

FEBRUARY 2004

you to read, test, and set registers or other memory locations at the bit level. They are great for reading buttons or registers, or changing a regis-ter's contents rapidly.

Another unique thing about IsoMax is the way it handles flow control. While its FORTH underpinnings are available for stodgy FORTH users, IsoMax prohibits the use of loops in procedural sections entirely. IsoMax allows you to have running indexes to track how many times things have been run, which is really the essence of using a loop. In IsoMax™, if you put an endless loop inside the procedural portion of a Virtual Machine, I guarantee you the system will crash.

Another interesting addition to IsoMax is finite state machine flow control, or FSM. This is a novel approach to programming embedded systems, and has real applications in the fields of control and robotics. State machines perform a function similar to if-then-else statements, but the end result is a direct line to the output you are interested in, not a rat's nest of multiple nested conditionals. This results in easier programming and faster program execution, because you only test inputs related to a particular state, instead of all possible inputs and computations every time.

In IsoMax, a Mealy model of state machine is used, as they tend to be more efficient in the number of states required. But Moore model machines can also be simulated in the language. State machines are close in concept to inference engines used in expert systems and Artificial Intelligence, and some are implemented that way. Today, state machines are seeing wide usage in the video game industry, and are particularly useful for communications protocols, and compiler design.

Overall, the IsoPod is an extremely flexible system on a board. To illustrate this point, I have shelved my PICs, 68332s, and 68HC11s in favor of the IsoPod. It's the micro I like to reach for first! NV