MCUBoot Compressed update on nrf52833 - Ram utilization

RE: MCUBoot Compressed update on nrf52833 - Ram utilization

KWolfe81 — Sun, 28 Sep 2025 14:44:11 GMT

Delta/differential upgrades are a fantastic solution if your customers don't mind the linear upgrade path requirement. Unfortunately, wouldn't work for us.

RE: MCUBoot Compressed update on nrf52833 - Ram utilization

longrain — Sun, 28 Sep 2025 07:13:14 GMT

Thanks a lot for sharing!
For the same reason, I switched to differential upgrade.

RE: MCUBoot Compressed update on nrf52833 - Ram utilization

KWolfe81 — Thu, 25 Sep 2025 22:06:07 GMT

Ok, it is literally that easy. Why, oh why, nordic, didn't you just make this a config option? As a follow-up, to sign/compress your image with the updated dictionary size, all you have to do is change bootloader\mcuboot\scripts\imgtool\main.py:

comp_default_dictsize=131072

I have compressed updates working with the nrf52833 and 64kB dictionaries. I'm sure it'll work with all other low RAM devices too.

RE: MCUBoot Compressed update on nrf52833 - Ram utilization

KWolfe81 — Thu, 25 Sep 2025 19:33:20 GMT

I probably shouldn't be commenting in real-time, but please tell me it's as easy as patching nrf\subsys\nrf_compress\src\lzma.c (yes, I'm aware I'll need to compress the updates with the equivalent dict size):

/* Assume the maximum LZMA dictionary size to limit the RAM buffer size for the decompressed
* stream.
*/
#define MAX_LZMA_DICT_SIZE (128 * 1024)

RE: MCUBoot Compressed update on nrf52833 - Ram utilization

KWolfe81 — Thu, 25 Sep 2025 19:19:38 GMT

Holy heck, this is never going to work:

Fixed dictionary size of 128kB?!? You guys know we're trying to program embedded devices here right? Sigh.