Executable loads over CF bootloader

[simonjwright]

The Crazyflie memory map has the bootloader at 0x08000000 and the main firmware at 0x08004000, whereas Certyflie loads at 0x08000000, thus overwriting the bootloader and preventing over-the-air updates.
I’m not sure how this could be easily corrected; the load address is fixed at low level in the runtime, so at first glance we’d need a new runtime. Perhaps the loader script could be parameterised.

[AnthonyLeonardoGracio]

Hi Simon,

Indeed, we already know this issue. I will discuss with my colleagues to see if we can provide a custom linker script with a load address set at 0x08004000 instead of using the one defined in the used runtime. We will keep you posted.

Regards,

[simonjwright]

I’ve done a bit of googling, and this works for me (it’s for an Arduino Due):

In the linker script,

START_OFFSET = DEFINED (START_OFFSET) ? START_OFFSET : 0;

MEMORY
{
    flash (RX)  : ORIGIN = 0x00080000 + START_OFFSET,
                  LENGTH = 512K - START_OFFSET
    sram (RWX)  : ORIGIN = 0x20070000, LENGTH = 96K
}

and then build with

gprbuild -P testbed -largs -Wl,--defsym,START_OFFSET=0x1000

This is like the way you already allow the stack size to be overridden (I’m not sure whether that is supported by a more user-friendly interface than the -largs one).

[Fabien-Chouteau]

Hi @simonjwright ,

There might be a problem with vector table address. I don't know how the bootloader works but the run-time was not tested in this configuration so there's a chance it won't be compatible.

Did you try yourself Simon?

[simonjwright]

It seemed to work! (aside from running away, as I said on issue #6).

start-rom.S says that VTOR is set in handler.S, but in fact it’s set in s-bbcppr.adb:

      VTOR := System_Vectors'Address;

so all should be OK.

[simonjwright]

Works for me: see linker script and corresponding GPR.

(These are from my project cortex-gnat-rts and my fork of this project to use that RTS, motivated by issue #6 here)