Prototyping A Tower

May 26, 2011
Technology editor Bill Wong takes a hands on look at Freescale's Tower development system. The latest Freescale processors have boards available for this stack.

Freescale MCF5225X Tower

MCF5225X Coldfile board

TWR-SER interface board

I wrote about Freescale's Tower development system when it was first available and I have had one in the lab for awhile. Well, it finally moved to the top of the stack. After working with it I can say that I am as impressed with the overall encounter as I was when I first saw the design.

For those new to the Tower system, it is designed for evaluation and prototyping. The Freescale MCF5225X Tower (Fig. 1) is a good example of the system that normally consists of a processor board plus one or more a peripheral interface boards. They are linked together with a pair of elevator modules that look like backplanes. They are backplanes although these backplanes are designed for peripheral interface distribution.

The Tower boards have edge connections on two sides. They can have connectors on the other two sides. The edge connections plug into PCI Express connectors on the elevator boards.

The elevator boards are not symmetrical and they do not support PCI Express at all. The connectors were chosed because they are cheap, reliable and handle high speed communication. One board is a parallel parallel bus with a little power hardware including a USB connector and power switch. There are two connectors on the opposite/outside of the board where special modules, displays in particular, can be attached.

The other elevator board is simply a PC board with connectors attached. It provides support and rigitidy to the system.

The kit I have includes the MCF5225X Coldfile board (Fig. 2) and the TWR-SER interface board (Fig. 3). The latter has serial and Ethernet connections. The processor board has jumpers, buttons, LEDs and some connectors for debugging but no peripheral connectors. That is what the tower is for.

The approach has advantages for prototypers because a simple two layer board can be designed and plugged into the system. It may not look as slick as some platforms but it is solid, cheap and easy to use.

The processor modules come with the Eclipse-based CodeWarrior Development Studio. This provides access to C/C++ as well as other languages if you go exploring.

The other big piece to the puzzle is Freescale's MQX RTOS. MQX RTOS has been around for quite awhile. It is available from Embedded Access. MQX RTOS is POSIX-compatible with a core set of facilities with a range of schedulers. Services like messaging and queues can be included as necessary. The operating system is integrated with the IDE.

All this software is one reason getting started took so long. Breaking out the cables and boards it just the start. It is faster to plug the boards together than to install all the software. It was time to have some fun once all that was done.

Another chunk of software are the Connectivity Labs included with the package. It takes a bit of time to run through them all but they provide hands-on experience with hardware and the operating system. These labs turned out to be a bit more complete than the typical introduction that some other development kits include.

Obviously experience with C is a prerequisite but otherwise the package does a good job of getting even the novice started. The sample applications are built around MQX. This provides a more sophisticated development environment but some may want to use a different OS or just drop an application on the board. That is possible but a bit more work.

In the end, the romp through MQX provided a good overview of CodeWarrior and the capabilities of the Coldfire, the board and operating system. I can only assume the packages for other processor boards will be the same. Boards can be purchased as a package or individually.

The Tower system has been used in a number of different areas. I'll be writing about C-Link Systems that has a number of boards for robotics. They also utilize Tower systems in a number of their robots.

Another robot that uses Tower processor boards is Freescale's own MechBot. The MechBot (see A Towering MechBot) uses a processor board that has peripherals on board. It can plug into elevator boards but the single board computer (SBC) is designed to operate on its own.

I like the Tower approach. I have not designed a custom peripheral board for it but the layout is simple and easy to work with. The ability to select from different processors and peripheral modules is very handy. They also tend to be inexpensive because there are no expensive connectors. Definitely check it out.

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