Tutorial: PWM with DMA on ARM/Kinetis

For a project I need to change the PWM duty cycle after a PWM period is over. One way to do this is to have an interrupt at the end of the PWM period, and then set the new PWM duty (compare) register value in the interrupt. That works fine for ‘slow’ PWM frequencies, but if the PWM frequency is high, the CPU load is massively increasing. A better way is to use DMA (Direct Memory Access).

FRDM-KL25Z with DMA PWM and Logic Analyzer

FRDM-KL25Z with DMA PWM and Logic Analyzer

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Semihosting with Kinetis Design Studio

Semihosting is a technique to do printf() debugging through an active debug connection. So instead using a physical connection like RS-232 or USB CDC, the connection to the host machine is through the debugger. This post is about enabling and using semihosting with gcc and newlib/newlib-nano in Freescale Eclipse based Kinetis Design Studio (KDS) using the GNU ARM Eclipse plugins.

Semihosting Console View with output

Semihosting Console View with output

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Configuration Data: Using the Internal FLASH instead of an external EEPROM

Many applications need to store persistent (non-volatile) data at runtime: configuration data, error logs, sensor data, calibration values, etc. The question is: where to store that data? If it is only a few kBytes, an SD card or similar is an overkill. Adding an external EEPROM? Sure, that works, but adds an extra part to the design. Some microcontroller have internal EEPROM. But what if not? Why not using the microprocessor internal flash memory?

Internal FLASH vs. external EEPROM

Internal FLASH vs. external EEPROM

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Tutorial: Freedom Board with Adafruit Ultimate GPS Data Logger Shield

Many times I start with a project and tutorial, only to get interrupted for emergency tasks and assignments. For a long time I wanted to add GPS (Global Positioning System) functionality to one of my projects. While I started a few months ago on this, it took me until this week-end to finish the at least the first part: a SD card data logger with GPS :-): I calculate global positioning and time information, can use it in Google maps and store it on a SD card:

Adafruit GPS Data Logger Shield on a FRDM-KL25Z Board

Adafruit GPS Data Logger Shield on a FRDM-KL25Z Board

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How to Add Register Details View in Eclipse

The standard Eclipse registers view only shows the core registers:

Standard Registers View in Eclipse

Standard Registers View in Eclipse

I think it would be great to have a view to see all the device peripheral registers too?

Embedded System Registers View

Embedded System Registers View

If you want the same, then this article is for you. It works both for stock Eclipse and Freescale Kinetis Design Studion (KDS) 🙂

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Reducing Compile Time in Eclipse with Parallel Build

Feeling that building a project in Eclipse (including Kinetis Design Studio) takes a long time? Then probably the ‘parallel build’ option is not enabled in your project: Using parallel build option reduces the needed time by factors. To give an example, to build a project with 56 source files takes 32 seconds without parallel build enabled:

no parallel build

no parallel build

With parallel build enabled this gets reduced down to less than 10 seconds:

Parallel Build Enabled

Parallel Build Enabled

🙂

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C/C++ Watchpoints with Eclipse Kepler

In “Watchpoints: Data Breakpoints” I used the Eclipse based CodeWarrior to set breakpoints so the debugger stops when my application is writing or reading a certain memory location. That CodeWarrior is based on an earlier Eclipse version, and things are different in Eclipse Kepler and not so easy to find. So here is how I can use watchpoints in Eclipse Kepler:

Watchpoints in Breakpoint View

Watchpoints in Breakpoint View

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Joystick Shield with nRF24L01 driving a Zumo Robot

With the Joystick shield I have a convenient way to drive and control a Zumo Robot without a wired connection:

Joystick Shield with Robot

Joystick Shield with Robot

While things started promising, there was a power supply problem at the end to be solved…

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GNU ARM Eclipse & Segger J-Link Device Name Settings

Thanks to the GNU ARM Eclipse plugins from Liviu it is easy to build and debug projects for all the different ARM cores. But I need to specify the device name in the debug configuration:

Device Name for Segger GDB Configuration

Device Name for Segger GDB Configuration

There must be an easier way for this? Yes, indeed, there is 🙂

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