STM32MP257F-DK (MB1605C) - No SWD communication with target, no boot, ST-LINK works fine

[MilanH]

Hi everyone,

I'm having trouble bringing up an STM32MP257F-DK Discovery kit (board reference MB1605C). ST-LINK itself works correctly, but I cannot get any communication with the main STM32MP257 processor, and the board never boots. I'd appreciate any insight into what else to check before assuming a hardware fault.

Board / setup:

• STM32MP257F-DK, main board MB1605, revision C-01
• Powered via USB-C into CN21 (USB PWR/STLINK)
• Using the original microSD card that shipped with the kit (preloaded OpenSTLinux demo image)
• Boot switches set to: BOOT0 = ON, BOOT1 = OFF, BOOT2 = OFF, BOOT3 = OFF (microSD boot)

What works:

• LD11 / power LEDs indicate the board is powered
• Windows enumerates two "STMicroelectronics STLink Virtual COM Port" devices (COM8, COM9) without issues
• STM32CubeProgrammer detects the ST-LINK probe: Serial number, FW version V3J15M6B5S1, Board correctly identified as "STM32MP257F-DK", Target voltage reads consistently 3.28-3.29V

What doesn't work:

• Connecting via SWD always fails with "Error: Unable to get core ID" / "Error: No STM32 target found! If your product embeds Debug Authentication, please perform a discovery using Debug Authentication"
• Tried all combinations of Reset mode (Software reset, Hardware reset, Core reset) and Mode (Normal, Hot plug, Under reset) - same error every time
• Tried Debug Authentication discovery (DA tab, "Discover" button) - fails with "Failed to communicate with target!"
• No output whatsoever on either virtual COM port at 115200-8-N-1, even right after pressing RESET
• The blue "Linux Heartbeat" LED (LED1) never lights up or blinks
• WAKE UP button press has no effect on any of the above

Question:
Given target voltage reads correctly but SWD/DA communication with the main processor fails completely regardless of mode, does this point toward a specific known failure mode (PMIC sequencing, DDR, SWD routing) I could investigate further, or does this look like a hardware defect requiring board replacement? Any suggestions for additional diagnostic steps would be very welcome.

Thanks in advance!

[AScha.3]

Hi,

first try connect with your actual boot/switch setting, connect in Programmer in DFU mode.

(as this should be dfu boot mode)

Otherwise…

to boot (OpenSTLinux) from MicroSD-card , set  BOOT0 = OFF, BOOT1 = ON, BOOT2 = OFF, BOOT3 = OFF (Binär: 0001) .

try…

 

[MilanH]

Update / Resolution:

Thanks for the pointers so far. For anyone finding this thread with the same symptoms, here's what turned out to be the issue and how I resolved it:

Symptoms recap:

• ST-LINK detected fine, target voltage read correctly (~3.28-3.29V)
• SWD connection always failed ("Unable to get core ID" / "No STM32 target found") in every Reset mode / Mode combination
• Debug Authentication discovery also failed ("Failed to communicate with target!")
• No output on either virtual COM port, no blue Linux Heartbeat LED (LED1)
• Boot switches correctly set for microSD boot (BOOT0=ON, rest OFF)

Root cause:
Connecting via USB DFU (CN16, "USB DRD" port) instead of ST-LINK showed the board was actually alive and enumerating in DFU mode (Device: STM32MP23xx/25xx, Device ID 0x505, CPU Cortex-A35). This meant the SoC's ROM code was running fine, but it kept falling back into USB DFU recovery instead of completing a normal boot - regardless of what was on the microSD card. This pointed to missing/corrupted RSSE (root-of-trust) partitions and/or FSBL, which the SoC needs before it can even attempt to load anything from the microSD card.

Fix:
Reflashed the board from scratch using STM32CubeProgrammer over USB/DFU, using the FlashLayout_sdcard_stm32mp257f-dk-optee.tsv from the latest OpenSTLinux Starter Package (v26.06.10), pointing "Binaries path" to the images/stm32mp2 folder. After flashing completed successfully and rebooting, LED1 started blinking (heartbeat pattern) and the console became available on COM8 (115200-8-N-1), with the board booting straight to a login prompt.

Takeaway for others with similar symptoms: if SWD/DA fails completely but the target voltage reads correctly, try connecting via USB (DFU) instead of ST-LINK before assuming a hardware fault - if the chip enumerates there, the SoC itself is fine and a full reflash of FSBL/RSSE via DFU may resolve it, even if the microSD card content seems irrelevant to the failure.

Thanks again for the help!