Category Archives: FreeRTOS

A popular open source real time operating system (RTOS).

FRDM with Arduino Ethernet Shield R3, Part 3: Embedded Web Server

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This is Part 3 of an ongoing tutorial to use the Arduino Ethernet Shield R3 with a Freescale FRDM-KL25Z board (or any other board you like).

In Part 1 I worked on the SD card, in Part 2 I have added basic network connection. Now time to run a web server with my FRDM-KL25Z :-). With this, I can get access to my board through the network, and the board will host a web page where I can do pretty much everything: showing status, or adding functions to turn on things like an LED 🙂

Web Server with W5100 on FRDM-KL25Z

Web Server with W5100 on FRDM-KL25Z

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FRDM with Arduino Ethernet Shield R3, Part 1: SD Card

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Sometimes it takes a very long time to realize a project. Adding the Arduino Ethernet Shield R3 to one of my Freescale FRDM boards is one of it: it took me a year until I have found a few days to work on using the Ethernet Shield with my FRDM-KL25Z.

FRDM-KL25Z with Ethernet Shield

FRDM-KL25Z with Ethernet Shield

I have not everything in place yet, so I decided to publish things in parts. So this is about part one: using the Micro SD Card on the Shield.

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Review: New FRDM-KL26Z Board

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I probably would have missed the fact that Freescale has released a new Freedom board, if I would not have visited my local distributor site to order a replacement for one of my first FRDM-KL25Z boards. So surprise, surprise: there is a new Freedom board: the FRDM-KL26Z!

FRDM-KL26Z Board

FRDM-KL26Z Board

So instead ordering again a FRDM-KL25Z, I decided to order that new FRDM-KL26Z instead. And it arrived right before Christmas, and now I had time to check it out. Nope, I did *not* use it as a blinking gadget on a Christmas tree, even if that would have been a nice idea ;-).

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RNet: A Simple Open Source Radio Network Stack

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I was searching the internet for an open source network stack for my nRF24L01+ transceivers. But these stacks were either too heavy or had a restrictive or not really non-open source license behind it. I was very reluctant to start with something I think already should exist. Two weeks ago I decided that I just do it from scratch, and here I am: I have the basics working 🙂

Two FRDM-KL25Z with nRF24L01+ Transceivers

Two FRDM-KL25Z with nRF24L01+ Transceivers

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FreeRTOS for the Freescale DSC 56F8400 Core

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Yes, I have been busy with all the different ARM Cortex Mx cores I’m using in my projects. But beside of the ‘ARM domination of the world’, there are other interesting processors out there. While the ARM cores have added DSP (Digital Signal Processing) capabilities blurring the boundaries between pure MCU and DSP processors, there is still a place (or niche?) for specialized DSP processors. The power of such processors is in the domain of fast signal processing, e.g. for intelligent power switches or for advanced motor control.

TWR-56F8400 Board and Box

TWR-56F8400 Board and Box

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Tutorial: Using the FRDM-KL25Z as Low Power Board

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The FRDM-KL25Z is a great board: inexpensive (around US$15), small form factor, has easily accessible pins, and has a low power (capable, at least) microcontroller, and comes with an embedded debugging interface. So why not using this board right away ‘as is’ for a low power battery operated device? Great idea, you think? Yes, I thought too. Only to find out that the board needs 20 mA out of the box.

The good news is: It is possible on a week-end to get this 150 times better down to 132 μA, with an RTOS running all the time :-). I invite you to join a journey with board modifications, jumpers, schematics and many multi-meter pictures ;-)….

132 micro amps

132 micro amps!

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Optimized FreeRTOS: Stack Check and SysTick for ARM Cortex Cores

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The ARM Cortex specification includes the ‘SysTick’ (System Tick Timer): a dedicated system timer which is intended to be used as time base for an RTOS. While technically it would be possible to use any periodic interrupt timer, I’m using as well the SysTick for my FreeRTOS ARM ports. And because Processor Expert includes a nice timer interface, I’m using the TimerUnit_LDD:

TimerUnit LDD for SysTick

TimerUnit LDD for SysTick

While this is great for flexibility, it has its price in efficiency. That TimerUnit_LDD adds overhead. So I want to get rid of the TimerUnit_LDD and use a more efficient way.

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DIY Free Toolchain for Kinetis: Part 5 – FreeRTOS Eclipse Kernel Awareness with GDB

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So far I have covered in this tutorial series how to install ARM GNU gcc, adding Eclipse, followed by adding GNU GDB debugger, and then adding Processor Expert. I’m using FreeRTOS a lot in my projects, and luckily there is a Kernel Awareness Plugin available for FreeRTOS for GDB in Eclipse. This tutorial is about how to install and use it.

Queues and Tasks

Queues and Tasks

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FreeRTOS V7.5.0 released

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A week ago, the updated FreeRTOS V7.5.0 has been released on FreeRTOS.org. So time to have my Processor Expert FreeRTOS component updated as well :-).

FreeRTOS V7.5.0

FreeRTOS V7.5.0

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