Issue 102 January 1999
In the Face of Medusa
Part 1:Developing Reliable Control

Start • Enemy Identification • Flying The 4Q • Roll The Camera • The Central Site • Sources and PDF

Sometimes it makes good sense to augment the power of a ’386 or ’486 embedded system with additional peripheral processing. Sure, you could design a system solution using just the ’x86 or Pentium platforms, and most of the time, that would be the best solution. But, sometimes it’s not.

By using smaller and less expensive peripheral processors to support a good ’x86 design, you can cut costs and complexity. Placing a subordinate processing platform in a specific job role offloads cycles from the main embedded processor and breaks the code into more manageable pieces. If the peripheral processor scheme is well thought out, a gain in overall system productivity is possible.

Think of it this way. Your ’x86 is busily cranking away on numerical calculations when an interrupt or clock event signals that it’s time to perform some I/O. Instead of sending a quick command to a peripheral processor to move a motor or turn on a valve, you stop your number crunching to take care of it from the ’x86 firmware or hardware.

Now that you’ve initiated the process from the ’x86 system, you also have to make sure it completes successfully. Another burden on your already busy ’x86 CPU, and you can’t continue your calculations until you finish the I/O operation.

The ultimate answer is to buy some expensive multitasking, multithreading OS and pile on the expensive CPU, megs of memory, and I/O hardware. You could do that or….

MARK IS IN THE BUILDING

Once again, I managed to get my hands on some real flight hardware from my friend Mark, "the Orbiter machinist." Seems there’s intelligence needed for a ground support unit that squirts water into petri dishes to grow plants. Take a look at Photo 1 and you’ll know why it’s named Medusa.

But, Medusa’s not the whole story. Intelligence is also needed to move a CCD camera over the petri dishes to take pictures of the growing and feeding process. As with most experiments of this type, there’s a myriad of pumps and valves that need attention, too.

A perfect solution for this baby is an embedded ’386 or better embedded system. By the way, this baby also needs to have its temperature checked and its diaper looked at as well. Can a single embedded platform, all dressed up in the proper hardware, provide the perfect solution? Well, sorta.