OTA over UART on nRF54L15 - Upload completes but firmware doesn't boot

RE: OTA over UART on nRF54L15 - Upload completes but firmware doesn't boot

Amanda Hsieh — Fri, 07 Aug 2026 14:18:55 GMT

Are you able to reproduce the issue on nRF54L15DK?

I suggest you use nRF54L15DK to familiarize yourself with Exercise 1 - DFU over UART - Nordic Developer Academy, then move to your custom board.

RE: OTA over UART on nRF54L15 - Upload completes but firmware doesn't boot

Venkatakishore — Fri, 07 Aug 2026 14:05:10 GMT

i Amanda H,

Thanks for your guidance. I am now able to build the code successfully.

Current Status:

Build succeeds without errors
Flashed the firmware over J-Link to my custom boardFile flashed: D:\Venkatakishore\Fleet_Panda\Lora_NRF\Gansan\nrf_devzone\ncs-inter-main\l9\l9_e1_sol\build\l9_e1_sol\zephyr\zephyr.hex
Configured UART pins in the mcuboot.overlay file (attached for reference)
/cfs-file/__key/communityserver-discussions-components-files/4/5280.mcuboot.overlay

The Issue:
When I try to perform OTA using AuTerm:

I connect to the specific UART port
I select the .signed.bin file (peripheral_nus.signed.bin)
I click "Go" (Upload)
The progress stays at 0% and I get the error:

"Timeout (Mode: Upload firmware)"

Attachments:

mcuboot.overlay file
Screenshot of AuTerm showing the timeout error

My Configuration:

Item	Details
Board	Custom board (nRF54L15)
NCS Version	v3.2.4
UART for OTA	UART30 (P0.01 TX, P0.00 RX)
Tool	AuTerm v0.35a
Build	Official `l9_e1_sol` solution

What I've Checked:

✅ The UART pins are correctly configured in mcuboot.overlay
✅ The board is powered on and connected
✅ The correct COM port is selected in AuTerm
✅ Baud rate is set to 115200
✅ The .signed.bin file exists and is not empty

My Questions:

Is there any specific configuration required in the custom board overlay for UART OTA to work?
Could the timeout be due to incorrect UART pin mapping in the bootloader?
Do I need to enable any additional Kconfig options for Serial Recovery on a custom board?
Is the mcuboot-button0 and mcuboot-led0 alias mapping correct for my custom board?
Could this be related to the SB_CONFIG_PARTITION_MANAGER or SB_CONFIG_MCUBOOT_MODE_SINGLE_APP settings?

I would appreciate any guidance on resolving this timeout issue.

Thank you for your time and support.

Regards,
Venkata Kishore P.

RE: OTA over UART on nRF54L15 - Upload completes but firmware doesn't boot

Amanda Hsieh — Fri, 07 Aug 2026 12:58:40 GMT

Hi,

I cannot reproduce the issue.

Please try to delete the build folder and rebuild.

-Amanda H.

RE: OTA over UART on nRF54L15 - Upload completes but firmware doesn't boot

Venkatakishore — Fri, 07 Aug 2026 12:11:50 GMT

Hi Amanda H,

Thank you for your response and for providing the link to the official solution.

1. NCS Version:
I am using nRF Connect SDK v3.2.4.

2. Build Issue with the Official Solution:
I attempted to build the official solution (l9_e1_sol) from the GitHub link you provided:
https://github.com/NordicDeveloperAcademy/ncs-inter/tree/v3.2.0/l9/l9_e1_sol

However, the build fails with the following error:

region 'FLASH' overflowed by 2296 bytes

Full Error Log:

FAILED: zephyr/zephyr_pre0.elf
c:/ncs/toolchains/fd21892d0f/opt/zephyr-sdk/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd.exe: zephyr\zephyr_pre0.elf section `rodata' will not fit in region `FLASH'
c:/ncs/toolchains/fd21892d0f/opt/zephyr-sdk/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd.exe: region `FLASH' overflowed by 2296 bytes
collect2.exe: error: ld returned 1 exit status
ninja: build stopped: subcommand failed.

3. My Environment:

Item	Details
Board	nRF54L15 DK (nrf54l15dk/nrf54l15/cpuapp)
NCS Version	v3.2.4
Toolchain	Zephyr SDK 0.17.0
Build Command	`west build -b nrf54l15dk/nrf54l15/cpuapp`
Solution Tested	https://github.com/NordicDeveloperAcademy/ncs-inter/tree/v3.2.0/l9/l9_e1_sol

My Questions:

Are there any specific configuration changes required for the nRF54L15 to reduce the firmware size?
Is there a known issue with NCS v3.2.4 and the nRF54L15 regarding flash size?
Could you please provide a minimal configuration that works for this board?

I would appreciate any guidance on resolving this build issue so I can proceed with testing the OTA over UART functionality.

Thank you for your time and support.

Regards,
Venkata Kishore P.

RE: OTA over UART on nRF54L15 - Upload completes but firmware doesn't boot

Amanda Hsieh — Thu, 06 Aug 2026 12:17:51 GMT

You can use https://github.com/NordicDeveloperAcademy/ncs-inter/tree/v3.2.0/l9/l9_e1_sol.

RE: OTA over UART on nRF54L15 - Upload completes but firmware doesn't boot

Venkatakishore — Thu, 06 Aug 2026 07:31:20 GMT

Hi Amanda H,

I am currently using the following setup:

Board: nRF54L15 DK (nrf54l15dk/nrf54l15/cpuapp)
NCS Version: v3.2.4
Toolchain: Zephyr SDK 0.17.0

Could you please provide the corresponding resources or guidance for this NCS version so that I can proceed further?

Thank you for your support.

Regards,
Venkata Kishore P

RE: OTA over UART on nRF54L15 - Upload completes but firmware doesn't boot

Venkatakishore — Thu, 06 Aug 2026 05:07:57 GMT

Hi Amanda H,

Thank you for your response and for providing the link to the official solution.

1. NCS Version:
I am using nRF Connect SDK v3.2.4.

2. Build Issue with the Official Solution:
I attempted to build the official solution (l9_e1_sol) from the GitHub link you provided for my nRF54L15 DK. However, the build fails with the following error:

region 'FLASH' overflowed by 2296 bytes

Full Error Log:

FAILED: zephyr/zephyr_pre0.elf
c:/ncs/toolchains/fd21892d0f/opt/zephyr-sdk/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd.exe: zephyr\zephyr_pre0.elf section `rodata' will not fit in region `FLASH'
c:/ncs/toolchains/fd21892d0f/opt/zephyr-sdk/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd.exe: region `FLASH' overflowed by 2296 bytes
collect2.exe: error: ld returned 1 exit status
ninja: build stopped: subcommand failed.

3. My Environment:

Board :- nRF54L15 DK (nrf54l15dk/nrf54l15/cpuapp)

NCS Version:- v3.2.4

Toolchain:- Zephyr SDK 0.17.0

Regards,

Venkata Kishore P

RE: OTA over UART on nRF54L15 - Upload completes but firmware doesn't boot

Amanda Hsieh — Wed, 05 Aug 2026 17:02:43 GMT

If you are using NCS v3.2.0, you should use https://github.com/NordicDeveloperAcademy/ncs-inter/tree/v3.2.0/l9/l9_e1_sol.

RE: OTA over UART on nRF54L15 - Upload completes but firmware doesn't boot

Amanda Hsieh — Tue, 04 Aug 2026 12:37:17 GMT

Hi,

What NCS version are you using?

Could you try this https://github.com/NordicDeveloperAcademy/ncs-inter/tree/main/l9/l9_e1_sol?

Regards,
Amanda H.