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CC3235S: If I connect an external SPI Flash to a CC3235MODAS will it work exactly as a CC3235MODASF so far as programming is concerned?

Chris Miller79
Intellectual 460 points
Part Number: CC3235S
Other Parts Discussed in Thread: CC3235MODASF, UNIFLASH, , , CC3235MODS, CC3235MODSF

The CC3235MODASF seems to be unobtainable at the moment

If I design my PCB with space for a standard SPI flash chip to be connected to pins 13,14,15,117 wiil the resulting system behave exactly the same way as a CC3235MODASF from a software development and programming point of view?

I worry that the serial bootloader is going to a return a device ID which will tell UniFlash "I have no flash memory", making it impossible to load firmware to the part.

  • 0
    Guru 80035 points

    Hi,

    You cannot connect external flash chip to pins FLASH_SPI_. These pins are dedicated for production programming only. Module CC3235MODASF have integrated 4MB SPI flash inside already.

    Difference between CC3235S and CC3235SF is in the regard of internal execution flash (1M), not a SPI flash.

    Jan

  • 0 in reply to Jan D
    Intellectual 460 points

    Thank you for the response, and - OK - understood that those FLASH_SPI lines are exclusively for the integrated SPI.

    The question remains that if I can only purchase CC3235S, how can I use the application processor?   I realise this must sound like a dumb question, but I have spent some time trying to understand this through the documentation (including swra613b, which I'm starting to think doesn't apply to the CC3235 series)

    I wonder if the application processor can run from SRAM (assuming the bootloader can tell the application processor to do that), but if that is the case, is it possible to add further FLASH memory for the application?

  • +1 in reply to Chris Miller79
    Guru 80035 points

    Hi,

    In case of CC3235MODS code is executed from 256kB RAM. This RAM is shared for your code and variables, buffers, heap, etc. Your code is loaded into RAM by ROM bootlaoder from SPI flash integrated inside module after startup.

    In case you are using CC3235MODS device there is no way how to add execution flash to this module. Only way is exchange to module with CC3235SF.

    Difference between CC3235S and CC3235SF is that SF device have 1MB XIP flash. This allow execute much bigger code. But it does not mean that CC3235S does not have enough resources for many applications. Maybe you can start development with CC3235MODS and in case you will not have enough resources you can switch to CC3235MODSF.

    Jan

  • 0 in reply to Jan D
    Intellectual 460 points

    Ah - that makes sense, thankyou

    I will examine how big my applicatoin is, and determine whether I can live within the non-F version.

    I suspect my limiting factor will now be FLASH file storage, rather than code space (the application is a kind of data logger)

  • 0 in reply to Chris Miller79
    Guru 80035 points

    Hi,

    SPI flash inside module is same for CC3235MODS and CC3235MODSF. It is 4MB. But be aware that SPI flash inside module is not suitable for data-logging purpose (due to limited number write cycles and not supported append at sl_ filesystem).

    This link may to give you insights how looks memory consumption in real application.

    Jan

  • 0 in reply to Jan D
    Intellectual 460 points

    That link is indeed useful - thanks.

    So far as I can see, the M4 processor does not have a spare SPI interface, so I think my only option is to add an SPI-connected external flash and use "bit bang" for the SPI interface - I don't need a lot of speed. 

    I realise I'll have to 'roll my own' storage handling - that's fine.

    Does that sound right?

  • 0 in reply to Chris Miller79
    Guru 80035 points

    Hi,

    No. Application processor Cortex-M4 have one SPI and one I2C interface fully available for you. Also it have available interface for SD card.

    Jan

  • 0 in reply to Jan D
    Intellectual 460 points

    Ah - I see now.  The "Add SPI" was greyed out in syscfg, but I now see that is because I'd already allocated the GPIO pins for other purposes.  If I release those, then I can add SPI interface.  Thank you very much for your patience - I really appreciate you helping me in this way.  Hopefully this will be useful for others on the same journey!