Does the MBR decide not to copy a new bootloader if it's identical to the old one?

RE: Does the MBR decide not to copy a new bootloader if it's identical to the old one?

Moloch — Tue, 19 May 2015 19:20:29 GMT

No worries, thanks for getting me an answer!

RE: Does the MBR decide not to copy a new bootloader if it's identical to the old one?

Susheel Nuguru — Tue, 19 May 2015 07:44:17 GMT

you were right, it does compare, I will edit my answer. Sorry about that

RE: Does the MBR decide not to copy a new bootloader if it's identical to the old one?

Susheel Nuguru — Mon, 18 May 2015 20:51:19 GMT

i was told by one of the experts that it should not compare it because we wanted to keep the operation simple. I will look into the MBR code tomorrow and find out to rule out the uncertainty

RE: Does the MBR decide not to copy a new bootloader if it's identical to the old one?

Moloch — Mon, 18 May 2015 19:31:31 GMT

Are you positive? The behavior I'm seeing is the opposite --the Nordic MBR (SD 7.1.0) only copies the new BSL if it differs from the old one.

The reason I ask is because I use the last 1k flash page of my BSL like this:

--------------------------------- <-- End of page
|Settings that should be erased |
|    when the BSL is updated    |
---------------------------------
|     Last part of BSL code     |
|                               |
|                               |
--------------------------------- <- Start of page

But those settings atop the BSL code don't seem to change when the "new" BSL is identical to the resident BSL. However, in an experiment, I've found that changing a few of the new BSL's bytes (in a different flash page than the one above) caused the settings to get erased as I would expect.

RE: Does the MBR decide not to copy a new bootloader if it's identical to the old one?

Susheel Nuguru — Mon, 11 May 2015 14:20:02 GMT

Complete answer EDIT

Hi,

The SD_MBR_COMMAND_COPY_BL, does compare the old image with the new image. This is required because of the internals of how this copy is done.

The SD_MBR_COMMAND_COPY_SD, command does NOT compare the old image with the new image.