Hello everyone,
I am working on a custom board using an STM32F103 (LQFP48) and connecting it via ST-LINK V2 using the SWD interface.
However, when I try to connect, STM32CubeProgrammer reports:
Error: No STM32 target found!
The log shows that the ST-LINK is recognized, the voltage reads ~3.16V, but the MCU cannot be connected.
Additional details:
- ST-LINK V2 wiring: 3V3, GND, SWDIO, SWCLK, NRST
- Tried “Connect under reset” mode and reduced SWD frequency to 50 kHz — still the same error
- The board has a 10kΩ pull-up resistor on NRST and a 100nF capacitor to GND
- Power supply is stable at 3.3V
- Continuity test from the SWD header to MCU pins shows SWDIO (PA13), SWCLK (PA14), and NRST are all connected
- MCU is brand new and has no firmware flashed yet
My questions:
1. Besides wiring and power supply issues, what other reasons could cause ST-LINK to fail detecting the MCU?
2. Is there any way to check if the chip is locked at RDP Level 2 when we can’t connect at all?
3. Are there recommended methods to test SWD directly on the MCU pins to rule out PCB routing problems?
Thanks in advance!
