Everything you always wanted to know about Eclipse, Embedded Systems Programming, Software and Tools, or any topics of this blog, but where afraid to ask, then this page is for you.

Post a comment, and you might get an answer, either from myself or from the readers of this blog. Otherwise: the answer is always ‘42‘ 😉

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837 thoughts on “Q&A

  1. Hi Erich! great work on his blog ! I’ll use some of your code inside my project ! Quick question about the freeRTOS PE component. I seem to get lost with the priority scheme of freeRTOS, interrupt and your implementation of the freeRTOS component.

    I want to be sure of one thing : IDLE task is assigned priotity 0, I guess it’S the lowest priority, the priority we give in FRTOS1_xTaskCreate() (PE component) should be related to priority number of the free RTOS right ? not the priority of the interrupt.. which are inverted right ?

    lets says i create 2 tasks with your component :
    FRTOS1_xTaskCreate(tsk1, “Task1”, configMINIMAL_STACK_SIZE, &globalhost, 1, NULL);
    FRTOS1_xTaskCreate(tsk2, “Task2”, configMINIMAL_STACK_SIZE, &globalhost, 2, NULL);

    Task2 priority will be greater than Task1 ?



    • Hi Etienne,
      the FreeRTOS component is using the normal FreeRTOS priority scheme (nothing different). If you are new to FreeRTOS and the ARM Cortex interrupts, then I recommend that you have a read at the multipart tutorial starting at https://mcuoneclipse.com/2016/08/14/arm-cortex-m-interrupts-and-freertos-part-1/.
      Keep in mind that FreeRTOS priorities start with zero as the lowest priority, while the ARM Cortex priorities have zero as the highest urgency level.
      So yes, 0 (or tskIDLE_PRIORITY) is the FreeRTOS priority for the IDLE task. The RTOS itself runs with its interrupts (SysTick, PendSV and PendSvReq) at the lowest interrupt priority (15 for 4 priority bits).
      And yes, for your example, the Task2 his higher urgency than Task1 and this one has higher urgency than the IDLE task.
      I hope this helps,


  2. Hello, Erich! I really ensjoy your blog!

    I have a question about mbed, especially openSDA.
    I build a board based on FRDM-KL43Z.
    My trouble is my boards are doesn’t work in my PC. I think absent of bootloader is main problem. Can you teach me how install a new bootloader in a board? There is none-S/W in my board.

    Here is my board symptom.
    1. Power LED is working
    2. MCU USB port ack as USB serial. But it cannot use as storage.
    3. openSDA USB unack.



  3. Hi…in my case my boards are doesn’t work in my PC. I think absent of bootloader is main problem. Can you teach me how install a new bootloader in a board? There is none-S/W in my board.


  4. Hi Erich,
    I just noticed that NXP has a Low Voltage Hbridge PE component (LVHBridge) , and also a medium voltage Hbridge (MVHBridge) component that can be downloaded and work on processors like the K20’s with Processor Expert. Have you seen these before and do you have any experience with them?
    I found it because I want to make a stepper motor driver (microstepping) using discrete components on the theory that it could be better/cheaper than using a microstepping chip- these components look like the easy way to do so.



  5. Hi Erich,
    I am working on a project where I send short text messages between a K64F and an android tablet. I want the K64F to be a host and the tablet to be a device. How do I do this. Do I need an OTG cable.


  6. Hi Erich
    I am trying to modify your example using the Adafruit SPI friend. I want to use the Freedom K64F instead of the Tiny20.

    For the Adafruit SPI you use 5 IO lines. I want to use the Adafruit UART friend, no interrupt and the CS tied to GND. This will use up only 2 IO lines.

    Will this work?



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