Element 14 XL_Star Review

Last week I received an Element 14 XL_Star board from Farnell/Newark. My condition for receiving this board was that I do a review. I must admit that I have been on a quest for the perfect controller board for a very long time. In my journey I have gone though pic microcontrollers, Parallax Basic Stamps, Arduinos and Arduino clones, TI MSP430s, mbed rapid prototyping and last the LeafLabs maple controller.

At the heart of the XL_Star is the Freescale MC9S08MM128CLK a very inexpensive 8-bit microcontroller with some impressive specs including a clock speed up to 48Mhz, USB, 128KB flash, 12Kb ram, 4 differential 16bit ADC ports. 8 single ended ADC ports, single 12bit DAC, and 47 GPIO. Also on the board includes a second freescale processor primarily used for programming and debugging the Freescale MC9S08JM60CLD. Last as a bonus feature, this board includes a three axis 14bit accelerometer the MMA845QT.

Software install

I was really hopping that this environment would have Linux support, however that was not the case so I started up an Windows 7 machine in Virtual Box. The CD has a wizard to help guide you though installing all the software and drivers necessary.

This process took a long time, roughly 30min. CodeWarror is a very large package that kept constantly asking for verification to install system drivers. Then on top of that you have to install a couple patches along with updated drivers.

After the install is complete you can start the application and select the Sample XL_STAR project to open the default program

Programming and Debugging

At this point I plugged in the USB to the bottom debugging port and selected “Debug” (F5) from the project menu. Another window opened that showed the source along with the assembly dump, registers and memory.

I must say that this real time debugger is a very cool feature. You start the program by either stepping though the line of code or hitting the start button. You get interactive feedback while the program is running. I ran the default program that shows the data from the accelerometer.

I also tried to modify the code to write my own custom program. This program will uses the led circle method to display a growing circle in a infinite loop.

while(1) {
    for(i=0;i<6;i++) {
        leds_circle(i);
        millisecond_delay(100);
    }
}

Conclusion

I must say that this is a very sophisticated board for it’s price.  I have very mixed feelings about the software. I would really like a Linux option. It may be a future possibility since Freescale does offer tools for linux. Their web page indicates that any download are for evaluation only unless your purchase. The active debugging was a very neat feature that I have not had in the past. I am going to have to spend a lot of time learning more about this board so far I get the impression that it is very complex and the tools are not as user friendly as the microcontrollers I am normally used to running. I hope to incorporate this board in some future projects