Store the application in external flash

[Stanley]

Hello, If I use the nRF51822 with 128KB ROM and I connect to a external flash via SPI.

The SoftDevice and bootloader are stored in the internal 128K ROM.

Is it possible that I store my code(application) in the external flash and the nRF51822 works normally?

Does the CPU get code from external flash on run time?

If it is possible, how to do it?

If it doesn't make sense, why?

Thanks.

[endnode]

Hello Stanley,

I guess you have a problem with MCU architecture: it must run the code from some valid memory address and you cannot map external flash to the memory model. So the only options is to boot from internal flash (ROM as you call it for whatever reason) and load the code to RAM. And because you have most probably less available RAM then internal flash there seems to be no benefit of doing it.

Cheers Jan

[endnode]

That's absolutely clear, using lower flash/RAM options on nRF51 or nRF52 make sense only if you are really sure that you fit there (including your corner cases such as OTA FW upgrade and new features added into code) and you manufacture in reasonably big series so BOM cost will bring you some margin.