March 1998, Issue 92

Picking a PC RTOS

Another thing to consider is licensing. RTOS vendors usually sell you their toolset and development system, which includes a one run-time license. This package lets you develop a prototype and debug it.

In some cases, like when you are designing a one-off system, this is enough. However, when you’re building embedded systems which may be used as a product or installed in several systems, you need to purchase more run-time licenses.

This process varies with each RTOS vendor. Typically, the cost of each run-time license is cheaper the more units you plan to sell, and in some cases, site licenses or unlimited licenses can be purchased.

This pricing can be an important issue in selecting an RTOS. What if the best-suited RTOS for your application has a run-time licensing structure, which makes your product too expensive?

Finally, it seems some RTOS vendors think the weight of their documentation makes it worth more. However, more is not necessarily better. Manuals should be concise and organized in such a way that it’s easy to find information quickly. Also, I like a quick tutorial and sample code in any documentation.

I’d also love to see more on-line documentation. Chorus Systems, now part of Sun, publishes their documentation in HTML format so it can be read on any system with a Web browser. This feature makes it easy to look up something quickly, like when I’m sitting in an airplane, frantically trying to finish this article in time for the deadline.