Hi Jacob,
On Sun, Jan 08, 2017 at 01:04:54PM -0700, Jacob Rosenthal wrote:
> On Mon, Jan 2, 2017 at 2:46 PM, Christopher Collins <[email protected]>
> wrote:
>
> > Do you know how big your loader is currently?
>
>
> Well, could be anything based on how much Im trying to strip from the
> nimble stack at any given time. but Im generally fighting to fit it within
> one slot which on the nrf51 is 110kB.
Yeah, it is currently pretty tough to get the OS + BLE stack to fit in
110kB. Hopefully we'll get a chance to reduce the size of NimBLE soon.
> I'm also not sure if it would buy
> > you much extra flash space.
>
> At this point Its not even about buying space, as I now have my other 110Kb
> back from the second image slot.. What I dont have anymore is update
> capability, so its about restoring that capability.
>
>
> > Im somewhat unclear if the 'loader' app can/should also serve as the
> > 'bootloader', or if it was intended that a separate bootloader would also
> > be present in addition to loader and application?
> >
> > This question of mine got buried above.. in this scenario, the distinction
> between loader and bootloader gets weird... My thought is theyre merged?
Sorry, I must have missed that question. The boot loader is present in
the split image setup. Here is how the boot sequence would look for the
various image setups:
1. Single image
* no boot loader
* image at address 0
* hardware boots directly into image
2. Stub image
* boot loader at address 0
* hardware boots into boot loader
* boot loader jumps to image in slot 0
3. Unified image (dual bank)
* boot loader at address 0
* hardware boots into boot loader
* if required, boot loader swaps images in the two image slots
(i.e., if an upgrade or a fallback is being performed).
* boot loader jumps to image in slot 0
4. Split image
* boot loader at address 0
* hardware boots into boot loader
* if required, boot loader swaps images in the two image slots
(i.e., if an upgrade or a fallback *between two loaders* is being
performed).
* boot loader jumps to image in slot 0
* loader in slot 0 jumps to "app" in slot 1.
The boot sequence and upgrade procedure for the split image setup is a
bit complicated. I have been working on some documentation for this
area, but haven't quite finished it. I hope to have something ready in
a day or two. In the meantime, please feel free to ask any follow up
questions.
Thanks,
Chris
