I cannot see the connections in the pictures nor the pinout of the DAPLINK, but the removed jumpers are ok. You need to connect the GND between the boards, for sure, and VDD 3.3V as you said required by your DAPLINK. The SWDIO goes to PA13, that is on pin 13 of CN7 The SWCLK goes to PA14, that is on pin 15 of CN7
Probably you have simply swapped SWDIO and SWCLK. Or, the firmware in the STM32F446 is blocking the SWD interface. Without a NRST driven by the DAPLINK, you can try to keep pressed the black reset button of the Nucleo board, while starting OpenOCD. This would prevent the FW to start and to reprogram the SWD pins. --- **[tickets:#465] CMSIS-DAP SWD: "SWD ack not OK @ 0 JUNK" and "Error connecting DP: cannot read IDR" ** **Status:** new **Milestone:** 0.12.0 **Created:** Thu Feb 12, 2026 03:48 PM UTC by Shreyas Acharya **Last Updated:** Sat Feb 14, 2026 11:44 AM UTC **Owner:** nobody **Attachments:** - [Screenshot 2026-02-12 211553.png](https://sourceforge.net/p/openocd/tickets/465/attachment/Screenshot%202026-02-12%20211553.png) (47.4 kB; image/png) Hi, I’m trying to program/debug an STM32F446RE (Nucleo-F446RE target MCU) using a CMSIS-DAPv2 probe (DAP103 Bluepill CMSIS-DAP). OpenOCD fails to connect over SWD. Symptoms: - Repeated: "SWD ack not OK @ 0 JUNK" - Final: "Error connecting DP: cannot read IDR" What works: - Flashing the same firmware via onboard ST-LINK works (program + verify OK). What fails: - Using CMSIS-DAP from OpenOCD/PlatformIO. Earlier I also saw OpenOCD start without interface cfg and error: "Can't find openocd.cfg" and "Debug Adapter has to be specified" until I forced the command line. OpenOCD version: - xPack OpenOCD 0.12.0-01004-g9ea7f3d64-dirty (2023-01-30) Command used (direct OpenOCD): openocd -d4 -f interface/cmsis-dap.cfg -f target/stm32f4x.cfg -c "transport select swd; adapter speed 100; init; reset halt; exit" Platform/OS: - Windows (MSYS2/MINGW64 terminal) Wiring: - CMSIS-DAP GND -> target GND - SWDIO -> SWDIO - SWCLK -> SWCLK - NRST -> NRST (optional / please advise) - VTref/VTarget -> 3.3V (if required by CMSIS-DAP) Notes/questions: 1) Could ST-LINK be contending on SWD lines on Nucleo-F446RE when using an external probe? If yes, what’s the recommended way to disconnect ST-LINK from the target? 2) Any recommended OpenOCD settings for CMSIS-DAP (connect_under_reset/reset_config, lower speed, etc.)? Full log (debug_level 4) attached below: --- Sent from sourceforge.net because [email protected] is subscribed to https://sourceforge.net/p/openocd/tickets/ To unsubscribe from further messages, a project admin can change settings at https://sourceforge.net/p/openocd/admin/tickets/options. Or, if this is a mailing list, you can unsubscribe from the mailing list.
