• State Not Answered
  • Replies 10 replies
  • Subscribers 74 subscribers
  • Views 210 views
  • Users 0 members are here
Attachments (0)
Nordic Case Info
  • Case ID: 343742
Options

UARTE21 and SMP Bluetooth conflict on nRF54L15 – works only with debugger attached

Agustin Perez

Hi,

I'm working with the nRF54L15 SoC and running into an issue when using UARTE21 together with SMP over Bluetooth. Here's what I’ve observed:

  • UARTE21 works perfectly when Bluetooth is disabled.

  • After starting BLE advertising using start_smp_bluetooth_adverts(), the UART output becomes corrupted and then freezes completely.

  • However, when running the same firmware with a debugger attached (using J-Link with VSCode), both UART and Bluetooth work fine simultaneously.

This is how I'm starting the Bluetooth SMP advertising:

#ifdef CONFIG_MCUMGR_TRANSPORT_BT
start_smp_bluetooth_adverts();
#endif

And here is a sample of the console output without the debugger (it freezes after this output):

uart:~$ ▒+)%%%HU▒Z▒▒
@▒▒ ▒▒▒C:3[m▒Y9▒▒▒▒▒▒[▒p▒▒-
1▒▒▒▒)R▒▒&

Some relevant parts of my prj.conf:

CONFIG_CLOCK_CONTROL_NRF=y
CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y
CONFIG_CLOCK_CONTROL_NRF_K32SRC_SYNTH=n

Additionally, based on advice from other tickets ( UARTE21 and SPIM20 on P2 issues ) , I’ve added the following code line in my application:

// Force constant latency mode
NRF_POWER->TASKS_CONSTLAT = 1;

Some conclusions:

  • This issue does not occur when using UART00—it appears to be specific to UARTE21. However, I need to use UARTE21 because the application requires SPI00.

  • A clear behavioral difference exists when running the application with vs. without a debugger.

We’re approaching pre-production, so resolving this issue is a top priority. Any insights, workarounds, or guidance on how to get UARTE21 working alongside Bluetooth SMP would be extremely helpful.

Thanks.
Related
Terms of service