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TM4C1233H6PM: Getting CMSIS device headers and understanting bit banding.

Tiago Costa71
Prodigy 80 points
Part Number: TM4C1233H6PM

Hi everyone.

I'm trying to learn how to use the bit banding region in order to toggle a GPIO pin. I think i understand how it works (writing to a specific address writes a bit on a specific register for example), however i cannot understand how to make it work in code.

I'm using the code in the bottom of this https://developer.mbed.org/cookbook/bit-banding page with the proper modifications to toggle pin 3 on the GPIO Port f (it's connected to a red led on the tm4c123gxl board).

It works fine if a set the bit on the GPIO_DATA register, but does nothing when using the bit band region.

(i'll post the full source when i get home. sorry about that)

Related to this problem, I cannot download the CMSIS DSP Header files. The only link i can find http://www.ti.com/tool/cmsis_dsp_headers, works but dosen´t provide the download button anywhere.

  • 0
    TI__Guru**** 244380 points
    Hello Tiago

    First of regarding the CMSIS DSP information, please refer to the following application report

    www.ti.com/.../spma041g.pdf

    As for the GPIO operation w.r.t bit banded, it would be simpler to use the TivaWare API's for GPIO Pin operations

    As an example, when using a GPIO Write

    GPIOPinWrite(GPIO_PORTA_BASE, GPIO_PIN_0 | GPIO_PIN_1, GPIO_PIN_1);

    This will set GPIO Pin-1 for Port A for the set of Pins 0 and 1

    Now if you wish to set 3 pins in a set of 5 pins, i.e. in the set of Pin 7, 5, 3, 2, 1 you want to set pins 7 and 3 then the same operation in TivaWare API would be

    GPIOPinWrite(GPIO_PORTA_BASE, (GPIO_PIN_7 | GPIO_PIN_5 | GPIO_PIN_3 | GPIO_PIN_2 | GPIO_PIN_1),
    (GPIO_PIN_7 | GPIO_PIN_3);

    The API works by using a set of pins given by argument 2 of the API and then applying the value as given by argument 3
  • 0 in reply to Amit Ashara
    Prodigy 80 points
    Hi!

    Thanks for taking the time to reply.

    I'm trying to learn how to use CMSIS and bit banding as mere curiosity for my hobby projects. For real projects i do use the TivaWare API because, as you said, it's simpler and it's one less thing to worry about when developing.

    I did look into the GPIO API functions and it looks like it uses the bit band region but i still cannot get it to work on my own.

    Regarding the PDF linked, i haven´t had the time to read it properly but it seems to be what i'm looking for. Thank you!