Electronic Design

EiED Online>> ColdFire: Hot Linux, Quick Quadros

The 66-MHz MCF5282 microcontroller is based on FreeScale's ColdFire architecture that harkens back to the Motorola 68000. This latest incarnation is significantly more powerful and is surrounded by a substantial peripheral complement, including controller area network (CAN), SPI, I2C, three serial ports with DMA support, and an eight-channel 10-bit queued a-d converter. The chip has background debug mode (BDM) and JTAG support, although the default interface for the M5282LITE kit is the serial port.

The M5282LITE kit includes the M5282LITE board (Fig. 1). The microcontroller incorporates 512 kbytes of flash and 64 kbytes of RAM. An additional 16 Mbytes of off-chip RAM and two Mbytes of flash provide a sizeable development platform for the Quadros RTXC real-time operating system (Fig. 2). A 10/100Base-T interface is part of the board, and is definitely the way to go for downloading and debugging once the basic system is up and running. An 8-MHz crystal drives the microcontroller's phase lock loop (PLL) to generate a clock up to 66 MHz. The board has headers for CAN and connectors for a serial port and Ethernet. There are bus and microcontroller interface connections, but the headers are not installed.

What makes the package is good documentation and a well-designed installation CD. A browser-based interface provides access to numerous Adobe Acrobat files covering everything from hardware configuration to application programming interfaces (APIs). It references the software-installation programs, so it's relatively easy to get up and running. A short, printed hardware setup guide lists board pinouts, port connections, and jumper configuration. It also introduces dBug.

dBug Serial Or ENet
The dBug command line debugger works with the serial port. It provides basic system configuration and breakpoint support. It is primarily used to configure the flash memory. You can download images into flash and RAM via the serial port, but it's much faster to use the Ethernet connection.

Ethernet support utilizes Trivial File Transfer Protocol (TFTP). Although support requires setting up a TFTP server on your workstation, this is a simple chore. It is possible to setup a default file name so fewer keys need to be pressed to download an application.

This interface is normally used for standalone applications, or to download a more sophisticated debugger interface. The sample application is built using Quadros RTXC and is downloaded via dBug.

Quadros RTXC RTOS and the MCF5282
Quadros was a good choice by FreeScale for a sample RTOS. uCLinux, which will be discussed later, is also suitable. However, uCLinux is a bit more resource-hungry, making the board a minimal platform. The Quadros RTXC operating system is available in a number of different versions and fits quite easily on the platform.

The package includes RTXC Quadros Single Stack LITE. While it limits you to half a dozen threads, it is possible to get a reasonable system running within these limitations. Check out my article "Single-Stack RTOS" (ED Online ID 9324) for more details on a single-stack operating system. Quadros has the typical multistack operating system that is also very suitable for a resource-limited system. The distribution CD has complete documentation, making the kit a good evaluation tool for RTXC.

I received a copy of the RTXC/mp multitasking RTOS from Quadros. It was easy to swap in a full-function multistack RTOS because Quadros' operating systems use a common API.

An open TCP/IP stack from OpenTCP is included with the package. It was initially developed by Viola Systems, which offers a range of rugged network devices and gateways. The stack is suitable for use with the Quadros operating system. Viola Systems also licenses its processor module technology that includes uCLinux support.

uCLinux and the MCF5282
The M5282LITE kit comes with the Windows-based Cygwin GNU toolset. You can download a compatible toolset for Linux and other development operating systems.

You can find a version of uCLinux that supports the board at SnapGear.org. It's relatively straightforward, but it does take a little tinkering to get things to work with the kit. Viola Systems is a better bet if you want something that works with minimal startup work.

The latest version is based on the merged Linux kernel, and uCLinux is now part of the 2.6 Linux kernel. Prior versions are also available at the site. Although it fits into the two Mbytes of flash, more would be handy. The use of network storage is a helpful alternative when using the kit for development work.

The kit does not include a GUI development environment. I use the standard Eclipse download with C/C++ Development Tools (CDT). CDT uses the GNU toolset, and works nicely with the tools that come with the kit.

FreeScale definitely provides a good package, even if you plan on using uCLinux as the operating system. Debugging applications via the Ethernet connection is fast and simple, although some device development may require BDM support. The board does have a BDM port. Definitely check out a BDM debugger if you plan on using the board for working on device drivers or standalone applications.

Getting Eclipse and uCLinux running takes some effort. It is definitely worth the effort if you plan on doing uCLinux development using GDB (the GNU project debugger) over an Ethernet connection.

Don't overlook ColdFire when checking out 32-bit platforms. It has a lot to offer and this kit makes it easy to evaluate.

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