Category Archives: CPU’s

Tutorial: Creating a Processor Expert Component for an Accelerometer

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If you are a frequent reader of this blog, then you know: I’m a big fan of Processor Expert components. While there are many Processor Expert components delivered with CodeWarrior, it lacks many components and device drivers beside of the normal on-chip peripherals. But value gets added to an embedded project with all the external devices, sensors and actuators. That’s why I have created many more components which are available on my GitHub site. Readers of this blog have asked several times to create a tutorial on how to create a Processor Expert component. So why not working on that on a long Easter weekend full of cold rain and snow?

So here we go: a tutorial how to create a Processor Expert component for the MMA8451Q accelerometer found on the FRDM-KL25Z board:

MMA8451Q Accelerometer on the FRDM-KL25Z Board

MMA8451Q Accelerometer on the FRDM-KL25Z Board

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Maze solving FRDM-KL25Z Robot goes backward for Dead-Ends

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The maze solving robot based on the Freedom FRDM-KL25Z and Pololu Zumo shield has new features:

  1. For dead-end paths, instead turning around, the robot is driving backward
  2. Higher speed for going forward/backward/turns
  3. In the finish area, the robot turns around
  4. It reverts the solution path, so the robot can directly run from the finish area to the start
FRDM-KL25Z Robot on Practice Area

FRDM-KL25Z Robot on Practice Area

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Freedom Logic Analyzer with DMA

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The FRDM-KL25Z Open Source Logic Analyzer based on SUMP presented here was already very useful with the added trigger support. But it was not capable to do a sampling rate above a few hundred kHz. That’s ok for slower probing, but not for anything with a higher speed. Using DMA (Direct Memory Access) instead of timer based sampling can remove that limitation :-).

FRDM-KL25Z used as Logic Analyzer on another FRDM-KL25Z board

FRDM-KL25Z used as Logic Analyzer on another FRDM-KL25Z board

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Compiling C Files with GNU ARM G++

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If I want a C++ project for my KL25Z Freedom board, I select C++ during the project creation:

C++ Project Creation for GCC

C++ Project Creation for GCC

This creates a gcc C++ project with all the needed settings.

This worked fine until I added a *.c file to my project which had code in it which was not accepted by the C++ compiler. Wait! Should the *.c not be compiled in C mode, as I was used to with other compilers? It turned out that things are different with gcc (or g++) :-(: the *.c files in my project are compiled in C++ mode. So the question is: how to compile in C mode with the ARM g++ compiler?

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Freedom Robot solves the Maze

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Finally I have found some time over the past week-end to enhance my Zumo robot. After I had my line following robot based on the Pololu Zumo chassis and the FRDM-KL25Z, I thought it should be easy and logical to solve a maze. Logical: yes. Easy: not that much. In fact it took me longer than expected. As always, there are a lot of tiny and important problems to solve (the maze alone was easy 🙂 ).

Zumo in the maze

Zumo in the maze

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Tutorial: PWM with Processor Expert

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For many of my applications I’m using a PWM (Pulse Width Modulated) signal. One example is the motor driver used in this project where I use one PWM signal for each motor. Another usage of PWM is to control the brightness of an LED. Processor Expert makes usage of the PWM hardware easier. Still, for some settings it is good to have the resulting signals in mind. So in this post I’m showing how the settings impact the PWM signal generated.

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mbed for the Freedom Board

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I knew about mbed already for some time: watching students using it for an NXP enabled board. Pretty cool stuff: mbed is an online IDE and compiler with tons of software libraries for the supported platform. So I was dreaming to have something like this for my own boards like the Freedom board. But because mbed only supported two dedicated NXP boards, that was a road block.

But then mbed announced recently that the mbed SDK is open source. Wow, that is interesting! And finally the announcement last week: mbed supports the KL25Z Freedom Board. Now they have my attention :-).

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Pololu Line Following Robot with Freedom Board

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Because my first line following robot was this week at the Embedded World conference in Nürnberg, I have constructed another one around the Freedom FRDM-KL25Z board. It is based on Pololu part items and the Arduino motor shield, plus using a Bluetooth module I have used in an ealier post.

Pololu Line Following Robot

Pololu Line Following Robot with FRDM-KL25Z

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USB MSD Host for the Freedom Board

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Sometimes things take longer than anticipated. And this is definitely the case for my USB MSD Host project where I wanted to use a USB memory stick with the Freedom FRDM-KL25Z board.

Memory Stick attached to the Freedom Board

Memory Stick attached to the Freedom Board

But finally, I have things working. At least most of the time ….

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