CubeMX thinks STM32N6 does not have DP-FPU

Bassett.David · ‎2025-10-06

Hello ST,

FYI - It appears CubeMX was not updated since DP-FPU capability was added to the STM32N6 data sheets.

Regards,

Dave

Ghofrane GSOURI · ‎2025-10-07

DP-FPU enables hardware double-precision floating-point calculations. In STM32CubeIDE, it’s activated by selecting FPv5-D16 as the floating-point unit and setting the ABI to Hardware implementation (-mfloat-abi=hard) in the project’s MCU settings.

Additionally, the startup code in system_stm32n6xx_fsbl.c configures the processor’s control registers to grant full access to the FPU by setting CP10 and CP11, ensuring that both secure and non-secure states can use the hardware FPU. Together, these settings guarantee that your application can efficiently execute both single and double-precision floating-point calculations using the microcontroller’s built-in FPU.

  /* FPU settings ------------------------------------------------------------*/
#if (__FPU_PRESENT == 1) && (__FPU_USED == 1)
  SCB->CPACR |= ((3UL << 20U)|(3UL << 22U));  /* set CP10 and CP11 Full Access */

  SCB_NS->CPACR |= ((3UL << 20U)|(3UL << 22U));  /* set CP10 and CP11 Full Access */
#endif /* __FPU_PRESENT && __FPU_USED */

Also

THX
Ghofrane

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Bassett.David · ‎2025-10-14

Hello Ghofrane,

I must apologize for not being more clear in my report. What I was noting is that the "MCU Selector" inside CubeMX does not show the STM32N6 when the filter "Core" "FPU" "Double-precision FPU" is checked. This corresponds to early datasheets for the STM32N6, but I was subsequently informed thet the STM32N6 DOES indeed have DP-FPU (happily!). I have confirmed this with the latest datasheet. I believe the selection filter in CubeMX should be updated accordingly.

I'm sorry to have created work for you in your nice response (above).

Regards,

Dave

Ghofrane GSOURI · ‎2025-10-14

Hello @Bassett.David

Thanks for bringing this issue to our attention.

An internal ticket 219691 has been raised to our dev team for resolution .

I will keep you posted with updates.

THX

Ghofrane

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