In case you have this problem with the FRDM boards: You are using the FRDM bootloader mode (it shows up as BOOTLOADER) or the MSD mode (e.g. it shows up as FRDM-KL25Z) (see OpenSDA on the Freedom KL25Z Board) and it does not respond any more, or does not work as expected, then read on…
If you are not in the academic world, then you might wonder about that ‘LaTeX‘ in the title. and no, it is not about that latex rubber material ;-), it is about ‘la-tek’ 🙂
In short, it is a programming language and tool set to ‘compile’ documents. Originally, TeX has been designed and mostly written by Donald Knuth and released in 1978. Since then, it has been evolved and TeX (or LaTeX) is widely used in academia.
Now I have implemented a watchdog with Processor Expert for my system. But what I have found out? I ended up with a looping system, and the watchdog did not fire 😦
What went wrong?
In my tutorial “Bits and Pins with Kinetis” I showed how to use the BitIO_LDD approach for Bit I/O access. I do not like this LDD (logical device driver) approach for several reasons:
Luckily, there is a way to hack around this 🙂
Self-Motivation: I write this post in the hope to cut the number of ‘please help me’ emails in my inbox ;-):
If you want to debug one of the Freescale boards with OpenSDA (FRDM-KL25Z, FRDM-K20, FRDM-KL05Z, FRDM-KL46Z48M, FRDM-KL02Z, TWR-KL47Z48M, …), and if you get this dialog …
No Device Available
… then read on.
Ahhhhrg! I admit: I’m not immune to all the silly problems an engineer can face in his life. And sometimes it is about the most basic things. This morning was again such a day: One of the infrared sensors of my Zumo Robot reported wrong values:
Sensor wrong values
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
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.
“A picture says more than 1000 words.”
I don’t know the source of that quote, but for sure it is true for every developer and engineer too. Engineers need to work a lot with numbers. But numbers can be transformed into pictures and graphs which can make complex things and relationships easier to understand. Verifying proper functionality of a PID closed loop controller or watching sensor values with a nice plot is definitely something very useful. Would it not be great to watch sensor data changing over time in a chart like the one below?
Accelerometer Graph
One way is to export data and then show it e.g. in Excel (which has been great chart functions). But even better, if this could be done directly with data provided from the target board? If you think this is hard to do, then I can show you how this can be done in a few steps with the help of a very nice tool: FreeMASTER 🙂
For many projects I need to store configuration or sensor data. For this I’m using either an SD card or program the internal flash memory of the microcontroller. Using the internal flash is a good thing as it does not need an external component. However, the typical number of programming cycles is limited to 10k-50k which is a limiting factor if data has to be recorded over a long time or very often. That’s why I’m using the very popular external 24xx external EEPROM devices from Microchip.
24LC512 connected to FRDM-KL25Z
What could be wrong with this code:
volatile uint16_t myDelay; void wait(uint16_t time) { myDelay = 0; while (myDelay<time) { /* wait .... */ } } void TimerInterrupt(void) { myDelay++; }?
