Thread: creating a data structure at specific memory location in c

  1. #1
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    creating a data structure at specific memory location in c

    I'm working on an embedded mcu that has two cores which can both see an area of memory beginning at 0x80000000.


    The ADC is connected to one core and a radio is connected to another. I want to write the data value received by the ADC to this memory address so that the other core can read it.


    Would somebody be able to help me figure out how to do this? The is no micro OS, it is bare metal.


    Would I create a pointer to struct at a specific address?


    I have two values in an array, how would I get them into the struct?
    Code:
    #define NUM_SAMPLES_POLLED (2)
    uint16_t samples_polled[NUM_SAMPLES_POLLED]

  2. #2
    Programming Wraith GReaper's Avatar
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    How much "bare-metal" is it? Does it have core-specific interrupts you can raise? Atomic memory instructions( LOCK etc )?

    What "struct" are you talking about?
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  3. #3
    and the hat of int overfl Salem's Avatar
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    Which compiler / toolchain are you using?

    This isn't complete, but does show you where you need to start looking.

    This is for GCC
    https://gcc.gnu.org/onlinedocs/gcc-6...ble-Attributes

    You start by annotating your data declaration like so
    Code:
    uint16_t samples_polled[NUM_SAMPLES_POLLED] _attribute__ ((section ("MY_FOO"))) ;
    Coupled with a linker script (see here), you'll be able to place that data at a specific location in the memory map.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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