MCO clock source for Nucleo L432KC board

Hello everybody,

I want to change the clock source for my Nucelo L432KC board to MCO clock. Reason is because I have timing issues when communicating to a SK6812 LED strip. However, I alaways get a SetSysClock Error on the serial output.

I am not really sure if I do the correct steps for changing clock source as I haven’t found a lot of information on that matter. I did the following:

  • Change of Jumper configuration
    - SB5 and SB7 now open (= solder bridge removed)
    • SB17 now shorted (= solder bridge added)
  • Change of targets.json in MBED studio
    • for “NUCLEO_L432KC”/“config”/“clock_source”/“value” changed to “USE_PLL_HSE_EXTC”

The program does compile/transfer but after start it directly fails.

Appreciate your ideas/hints what I do wrong here.

Serial error output:

++ MbedOS Error Info ++
Error Status: 0x80FF0100 Code: 256 Module: 255
Error Message: Fatal Run-time error
Location: 0x8004371
Error Value: 0x0
Current Thread: H?G<6>H Id: 0x0 Entry: 0x8000441 StackSize: 0x0 StackMem: 0x8000471 SP: 0x2000FEC4
For more info, visit:
– MbedOS Error Info –
SetSysClock failed

Yes, I think you face the same issue as the one corrected in:

Please, push a pull request when it works !-)



Thanks Jerome for your feedback. I also think it is a related issue. Search quite a lot during last night and found out that disabling the LSE at least solved the immediate issue and the board boots now. Thus, I added for the L432 board the following in the json target config:
"overrides": { "lse_available": 0 },