Category Archives: Kinetis

Slow 32 kHz Oscillator Startup

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In an IoT (Internet of Things, see “IoT: FreeRTOS Down to the Micro Amps“) project I’m using the Freescale KL15Z microcontroller. The nodes are moving around, and the board is using a special inductive charging ‘on the fly’ when nearby the charging station. The energy is stored in capacitors, so no batteries are needed. That worked very well, but some system failed: they need to quickly check sensor signals after power-up. Tracking down the problem, it was obvious that most of the systems failed because it took them too long to boot from the power-on reset. So I instrumented the application to toggle an LED so I can monitor what happens: It was over 400 ms after power-on! Yikes!

413 ms for startup

413 ms for startup

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Preventing Reverse Engineering: Enabling Flash Security

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Now I have invested a lot of time into my application, ready to be flashed on the devices and shipped. But wait: I don’t want that someone can read out the code from my device and have it reverse engineered. For this, I can ‘secure’ the device.

Flash Security Settings

Flash Security Settings

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Tutorial: DIY Kinetis SDK Project with Eclipse – Board Configuration

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In “Tutorial: DIY Kinetis SDK Project with Eclipse – Startup” I showed how to create a Kinetis SDK project from scratch. In this post it is about adding the board initialization files. With the board initialization the peripheral clocks and pin muxing is configured.

MK64FN1M0VLL12 on FRDM-K64F

MK64FN1M0VLL12 on FRDM-K64F

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Formula Student Electric “grimsel” Testing in Alpnach

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Here is another featured student project of this semester: Formula Student Electric (FSE). After the outstanding racing season with “Julier” in 2013, the students have designed and built a new and improved Formula Student Electric car “grimsel”, named after the Grimsel Mountain Pass.

Team Video:

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Programmable Ultrasonic Sensor Shield for FRDM Board

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“Note to myself: post articles about what students have done this semester…”

Students have turned in their semester project work. I have set for myself a goal to briefly describe to the ‘outside’ world what they did, as an inspirational source :-). So here is a first article about the project completed by Christoph Bühlmann who developed a shield for the FRDM-KL25Z board: a programmable ultrasonic shield:

Ultrasonic Shield with FRDM-KL25Z

Ultrasonic Shield with Freescale FRDM-KL25Z (Source: Christoph Bühlmann)

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Tutorial: DIY Kinetis SDK Project with Eclipse – Startup

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This is the start of a multi-post tutorial about the Freescale Kinetis SDK, released back in April as beta version. The SDK a set of peripheral drivers, and will become the standard software foundation and drivers provided by Freescale for their ARM Cortex based devices. Similar what other vendors already do. While this is a good step, it is the same time very disruptive for my university projects with new Freescale Cortex-M devices. And with everything new (and beta), it needs time to learn. So this post is about creating a Do-It-Yourself Kinetis SDK project from scratch for Eclipse. This part is about the startup code: about everything to get the application started.

FRDM-K64F with SD, nRF24L01+ and HC-06 Bluetooth

FRDM-K64F with SD, nRF24L01+ and HC-06 Bluetooth

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Tutorial: PWM with DMA on ARM/Kinetis

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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

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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

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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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