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Re: AVR constants in Flash

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  • clemens fischer
    On Sun-2011/09/04-18:46 Gregory N wrote in gmane.comp.embedded.nuttx ... Isn t this what the SECTIONS {...} linker ( info ld on linux-like cross dev
    Message 1 of 4 , Oct 2, 2011
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      On Sun-2011/09/04-18:46 Gregory N wrote in gmane.comp.embedded.nuttx
      (MID <j40a0s+2beg@...>):

      > Sounds interesting. NuttX is in C, but that should be okay right?
      > I don't know exactly what you are planning.. are you planning on
      > pre-processing C files in some fashion to move constant data to FLASH?
      >
      > Getting the data into FLASH is one issue; the other is accessing it
      > from FLASH. The biggest issue for me was printf and all of the printf
      > strings in RAM. Getting those into FLASH would really make the NuttX
      > console-based examples and lot easier to detail with.

      Isn't this what the "SECTIONS {...}" linker ("info ld" on linux-like
      cross dev environemnts) scripts are for? They put any block of code or
      data, whether initialized or not, into any conceivable memory location.

      Of course after running the linker the program "objcopy" would be needed
      to make an image that can be pushed to the device.

      Do the AVR micros have trouble with accessing data in flash?


      clemens
    • Gregory N
      ... Developing an AVR-specific OS is not a problem. I think the real difficulty is when you support an MCU-independent OS that runs on a variety of MCUs. Then
      Message 2 of 4 , Oct 2, 2011
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        > Isn't this what the "SECTIONS {...}" linker ("info ld" on linux-like
        > cross dev environemnts) scripts are for? They put any block of code or
        > data, whether initialized or not, into any conceivable memory location.

        Developing an AVR-specific OS is not a problem. I think the real difficulty is when you support an MCU-independent OS that runs on a variety of MCUs. Then such MCU-specific customizations become an issue.

        > Do the AVR micros have trouble with accessing data in flash?

        Yes.. Since the AVRs have a Harvard architecture, data in FLASH must be accessed in a special way since it is not in the same "address space" as SRAM.

        Greg
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