Unable to connect STM32N657Z0H3Q

[Vinayak_MK]

Hello friends,

Hardware Details

MCU: STM32N657Z0H3Q
Configuration: Custom PCB design
Boot Mode: Attempting USB Boot (BOOT0=HIGH, BOOT1=LOW)
Power: 1.8V system, SMPS for CORE (as per datasheet)

Problem Description
I've designed a custom PCB using the STM32N657Z0H3Q and I'm facing issues getting it to enter boot mode. When I connect the board to my PC with BOOT0 pulled HIGH and BOOT1 pulled LOW, the USB device is not recognized by STM32CubeProgrammer.
I've verified all power rails are providing the correct voltages. I've also tried multiple cables and USB ports to rule out simple connectivity issues.
Additionally, I attempted using ST-LINK for programming but that's failing as well, which makes me suspect there might be a fundamental issue with my circuit design.

What I've Tried

Confirmed all power supplies are providing expected voltages
Verified boot pin configurations (BOOT0=HIGH, BOOT1=LOW)
Tried multiple USB cables known to work with other devices
Checked connections against reference documentation

Questions

Are there any known issues with USB boot mode on this specific MCU variant?
Could anyone with experience on the STM32N6 series suggest common pitfalls with the boot configuration?
Are there specific requirements for the USB peripheral configuration I might be missing?

I've attached my schematic for reference. Any help identifying potential issues would be greatly appreciated!
Thanks in advance!

@Raghavendradp @S.Suriya PRAKASH 

[MikeF]

Hello,

I recommend you try to use ST-Link with dev-boot mode (BOOT1 - H, BOOT0 - X). 

ST-Link should be updated to last FW version. 

[RomainR.]

Hello @Vinayak_MK 

The Boot modes of STM32N6 is explained in the RM0486 section 9.1.2 Serial boot.

With the STM32N6 in DEV_BOOT (BOOT1=1) and using STLink debugger in SWD mode and STM32CubeProgrammer, could you check the OTP BOOTROM_CONFIG2 - OTP11, if the value of the bitfield [16:9] is not = 0x01 USB boot source disabled?
The correct value must be = 0x00 to enable all serial boot source (USB, UART...)

Otherwise, could you share the schematic to check the hardware and the USB PHY connection and powering?

Best regards,

Romain,

[Vinayak_MK]

Thank you so much @MikeF  @RomainR. for you immediate support.

We have found the issue and now the Board is up and we are able to program it.

The Boot pin was not properly pulling up the voltage and after fixing the USB got detected.

Thanks and looking forward for future supports!