DFU data not being written to external flash

RE: DFU data not being written to external flash

Ivenhor — Thu, 28 Aug 2025 10:13:04 GMT

Thanks that helped!

RE: DFU data not being written to external flash

Vidar Berg — Wed, 27 Aug 2025 10:17:58 GMT

Thanks. Yes, I was able to reproduce. The problem occurs when the chip enters low power mode between transactions. Your sample also worked when I added NRF_POWER->TASKS_CONSTLAT=1; to the beginning of main().

RE: DFU data not being written to external flash

Ivenhor — Tue, 26 Aug 2025 06:55:59 GMT

Yes, the problem reproduces on the devkit. I prepared an example based on our configuration.

So you can try it yourself.

repository

RE: DFU data not being written to external flash

Vidar Berg — Mon, 25 Aug 2025 12:25:23 GMT

Hi,

This seems very strange, and I haven’t been able to find any similar reports of it. Are you able to test the same code on a nRF54L15 DK to see if you get the same result?

RE: DFU data not being written to external flash

Ivenhor — Fri, 22 Aug 2025 10:23:44 GMT

Hi Vidar,

Thanks for the reply. Yes, the logs are enabled. No errors occur. Here’s some additional context from our testing:

We are writing 4 KB chunks to the external MX25R64 flash (secondary partition managed by MCUBOOT).
Flash dumps using nrfutil show that chunks are only partially written when not debugging: sometimes only the beginning, middle, or end of a chunk is actually stored.
No errors are reported by dfu_target_mcuboot_write(), and all Zephyr logging calls succeed.
When we run the DFU logic through a work queue instead of a separate thread, the writes succeed only if we add logging calls immediately before the write, e.g.:

for (int i = 0; i < 50; i++) {
    LOG_INF("Dummy log");
}
err = dfu_target_mcuboot_write(data->rx_chunk_buf, data->len);

We suggests a timing or synchronization issue. Logging seems to “help” the writes complete correctly. With this workaround, we were able to upload a full firmware image. We also observed an issue with the image swap: the swap succeeds only when debugging (the magic number is read correctly), otherwise the swap may fail.

RE: DFU data not being written to external flash

Vidar Berg — Thu, 21 Aug 2025 12:14:01 GMT

Hello,

I can't think of any explanation for why it works during an active debug session, but when not debugging, the app runs normally without errors but skips all writes to external flash. Is UART logging available on this board so you can check what happens when not in debug mode?

Best regards,

Vidar