Freedom Logic Analyzer with Triggers


The first FRDM-KL25Z Freedom Logic Analyzer firmware was missing one important feature: Triggers! But this weekend the firmware has evolved a bit :-).

Triggers

Trigger Settings

Trigger Settings

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DAC Example with the Freedom Board


After working on an ADC example, a DAC one was missing. Julio E. Fajardo is a reader of this blog, and he was so kind to send me an example project for the FRDM-KL25Z. The example is able to produce produce different waveforms with the DAC. The project has two examples which they are enabled/disabled in main(). One example waveform the sawtooth:

Sawtooth_FDRM_DAC

Sawtooth_FDRM_DAC

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Skipping Breakpoints


The challenge with small microcontroller like the ARM-Cortex-M0+ is that they have very limited debugging resources. As such, the number of hardware break points is very limited (see this post). For example for the KL25Z on the Freedom board, I only have 2 break points available if I want to do stepping:

No more hardware breakpoints available

No more hardware break points available

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Be Aware of the Baud Problem


I’m using serial communication in different flavors for my project: with the shell, with OpenSDA USB CDC, to use printf(), and with the Bluetooth module. Processor Expert is a big helper, but as for any software, it is not bug free. And there is a problem with Processor Expert in CodeWarrior for MCU10.3 in respect with Baud settings for a serial interface.

Probing the Bluetooth Module Serial Connection

Probing the Bluetooth Module Serial Connection

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Processor Expert Configuration Registers View


In “Using the Reset Button on the Freedom Board as User Button”, I had the problem to find out why a setting did not make it into my generated code. There is the fundamental question: “How does a setting impact my microcontroller register settings?”. There is an answer to that question: The Configuration Registers view:

Configuration Registers View

Configuration Registers View

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Bluetooth with the Freedom Board


I’m working now on a lecture robot project using my Freedom Board. And for this I need a wireless communication. I already have IEEE802.15.4 (SMAC) working, but I wanted to add Bluetooth as a low-cost option. I have found an inexpensive Bluetooth module which is available for only around $4-8 which we use in another university class project. The module is an AT command module: that means the microcontroller communicates with AT serial commands with the module, and the Bluetooth stack itself runs on the module. In a minimal configuration I only need 3.3V, GND, TX and RX plus a CMD (Command) pin:

Bluetooth Module

Bluetooth Module

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Tutorial: Using the ARM CMSIS Library


One of the great advantage of using an ARM core as on my FRDM-KL25Z board is that I can leverage a lot of things from the community. And one big thing around ARM is CMSIS (Cortex Microcontroller Software Interface Standard). It is an industry wide software library for the ARM Cortex microcontroller. Using the CMSIS libraries and interfaces will make it easier to port applications within the ARM Cortex family.

CMSIS Version 3 Block Diagram (Source: Arm.com)

CMSIS Version 3 Block Diagram (Source: Arm.com)

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