Category Archives: KL25Z Freedom Board

Everything around the KL25Z Freedom Board (FRDM-KL25Z)

A Processor Expert Component to Help with Hard Faults

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Ahrg! Again my ARM application crashed somewhere and I ended up in a HardFault exception :-(. In my earlier post I used a handler to get information from the processor what happened. But it is painful to add this handler again and again. So I decided to make things easier for me: with a special HardFault Processor Expert component :-).

After adding this HardFault component to my project, it automatically adds an entry to the vector table. So no manual steps are needed: having the component in the project and enabled will do the needed steps.

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LED’s for Kinetis, simplified

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Sometimes it takes a while until things get better. Same thing applies to software: from time to time a refactoring and simplification makes sense. Especially if the underlying technology has been improved. With CodeWarrior for MCU10.3 available, it is time to refactor the LED component.

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CSI Crime Scene Investigation with I2CSpy and Freedom Board

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The CSI is one of my favorite crime drama television series: not because it reflects the true reality, but because it is fun watching how they always find new ways how to investigate a crime scene with ‘close to reality’ tools. Real CSI is different: you only do a small part of the investigation chain. As for myself, I’m engaged in a research project at the university to develop hardware and software for crime scene investigation :-).

One area of that research project is to retrieve and data from credit card (ATM) skimming devices: these are devices are attached or inserted into credit or debit card machines and ‘skim’ the card information and the PIN code used. With that information, it is possible to clone a credit card for credit card fraud. Such devices are a big problem, and newer devices are very hard to spot. Simply ‘google’ for pictures for “skimming device” and you will get an idea of the diversity and madness of such devices :-(.

Microscopic investigation of skimming device

Microscopic investigation of skimming device

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HD44780 2×16 Character Display for Kinetis and Freedom Board

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In my earlier Nokia LCD post I described a ‘free of charge’ way to add a LCD display to my FRDM-KL25Z board. If that Nokia display is not available, or an alphanumeric display is enough, then the Hitachi HD44780 display is a low cost option as well.

The HD44780 (or compatible) display is one of the most common displays available. And they usually conly costs around $10 or less. I have used a ‘blue’ 3.3V version of such a display already in my lectures with a Freescale S08 microcontroller. So I thought it would be nice to port the driver to the Kinetis and the KL25Z on it.

LCD Boards with FRDM-KL25Z

LCD Boards with FRDM-KL25Z

A recent post of TKJ Electronics about such a really inexpensive (only $5) HD44780 display caught my attention. And finally I had two of such TKJ displays in my postal mail box yesterday. Time to have some fun on a weekend 🙂

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Zero Cost 84×48 Graphical LCD for the Freedom Board

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The Freedom KL25Z board has a great price of less than $15. Adding a typical LCD usually will add a multiple of that price to the budget. But hey, there is a way to add a LCD to that board at almost no costs! With the idea that I have an old outdated Nokia phone, and the cost of a small capacitor plus some wires are considered as ‘zero’ ;-).

Say Hello from the Freedom Board

Say Hello from the Freedom Board

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FRDM-KL25Z with the Arduino Motor Shield

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The great thing with the Freedom FRDM-KL25Z board is its compatibility with Arduino Shields: a great set of board available at very reasonable prices. I had my hands on the Adafruit Data Logger shield, and now it was time to use the original Arduino Motor Shield R3.

Freedom FRDM-KL25Z with Arduino Motor Shield and Arexx Chassis

Freedom FRDM-KL25Z with Arduino Motor Shield and Arexx Chassis

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Processor Expert Maxim I2C RTC for the Arduino Data Logger Shield

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There was one part missing to complete the software support for my Arduino DataLogger Shield on top of my FRDM-KL25Z Freedom board: support for the Maxim DS1307 RTC (Real Time Clock).

DS1307 on the Adafruit Data Logger Shield

DS1307 on the Adafruit Data Logger Shield (Source: http://www.ladyada.net/make/logshield/design.html)

Things got delayed a bit, as I first needed to get the I2C infrastructure up and running (see this post). But finally, I have things working :-). I proudly present: RTC_Maxim!

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KL25Z and I2C: Missing Repeated Start Condition

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I really hate this kind of stuff: I know it should work, but it does not. I’m loosing a lot of time (hours, days, even weeks) to track it down to the root cause. Yes, I create my own bugs. Yes, there are bugs in tools, sources, libraries and components. But what many might not believe: there are bugs in silicon too :-(. If you do not believe, here is one: there is a hardware I2C problem on the KL25Z used on the Freedom board. It worked in one project, but not in another.

❗ The silicon bug described here is present on many Kinetis devices, not only the KL25Z!

Logic Analyzer attached to the FRDM-KL25Z board

Logic Analyzer attached to the FRDM-KL25Z board

So if you are facing a problem where you read 0xFF or wrong values from the I2C bus with the KL25Z, here is probably why (and how to workaround it). The problem showed up with a modified version of the Freedom Accelerometer tutorial….

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Debugging Hard Faults on ARM Cortex-M

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It is as bad as this: my application stopped in an unhandled interrupt service routine:

Cpu_Interrupt
Cpu_Interrupt

That does not tell much. I’m using Processor Expert generated code, and with this all my ‘unhandled’ vectors are pointing the same handler:

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Arduino Data-Logger Shield with the FRDM-KL25Z Board

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One success factor of the Arduino platform is the broad availability so-called ‘shields’: hardware plugin-modules which extend the capability of platform. Shieldlist.org currently lists 288 different shields available! Clearly, Freescale wants to benefit from that ecosystem with the Freedom FRDM-KL25Z board which features Arduino compatible headers. Time to use the Freedom board with an Arduino shield :-).

Data Logger Shield on Top of Freedom Board

Data Logger Shield on Top of Freedom Board

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