Category Archives: Tips & Tricks

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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Finding Settings in Processor Expert Components

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Processor Expert components are making things very easy to configure: go a component, use the component inspector and change a setting. However, with the devices getting more and more complex, the list of settings or properties get longer and longer. To the point that it is hard to find a setting.

For example, where are the settings for the PLL in the CPU component?

Component with Settings

Component with Settings

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FILLing unused Memory with the GNU Linker

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In many of my applications I use a CRC/checksum to verify that the code/flash on the target is not modified. For this, not only the code/data in flash counts, but as well all the unused gaps in the memory map. Instead to leave it up to the flasher/debugger (which usually erases it to 0xFF), I want to fill it with my pattern. The GNU linker is using the pattern 0x00 for unused bytes inside sections. So this post is about to use the GNU linker to ‘fill’ the uninitalized FLASH memory with a pattern.

FLASH with DeadBeef Pattern

FLASH with DeadBeef Pattern

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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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Switching between ‘tabs’ and ‘no-tabs’ UI in Processor Expert

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Newer releases of Processor Expert (e.g. in Kinetis Design Studio (KDS)) come with a ‘graphical’ (or ‘tabbed’) view of the Component Inspector. The UI elements are different and ‘tabs’ are using:

Component Inspector in Tabbed View

Component Inspector in Tabbed View

I like much more the earlier ‘no-tabs’ view. Luckily, there is a setting to switch the view back.

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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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