Mbed Default Crystal HSE or HSI?

Mbed OS
1

Hiya,

When selecting a board in the compiler and for example loading a simple blinky program, is the board using the internal oscillator HSI or the external oscillator HSE?

2

Hello Muhammed,

By default, NUCLEO boards use the HSE clock signal coming from the STLink programmer/debugger attached to the board.
For any target board you can find the related info in the mbed-os/targets.json at master · ARMmbed/mbed-os · GitHub file:

  • Search for you board and then for “clock_source”. You should find something like:
            "clock_source": {
                "help": "Mask value : USE_PLL_HSE_EXTC | USE_PLL_HSE_XTAL (need HW patch) | USE_PLL_HSI",
                "value": "USE_PLL_HSE_EXTC|USE_PLL_HSI",
                "macro_name": "CLOCK_SOURCE"
            }
  • If no “clock_source” is defined for the given target board then it is using the “inherited” value. Check what value is defined for the “inherited” target.

Best regards, Zoltan