Impossible to access my STM32L011D3 with SWD

[Loïc]

Hello all,

So I've recently made a new PCB design with a STM32L011D3 chip. I also possess a BMP (bl*ck magic probe), that worked for other projects. So I am unable to see the chip with my BMP , when I do a swdp scan to list devices. The probe detects the 3V3 voltage, but then doesn't respond. When i unplug the GND cable, then these messages prompt on the "arm-none-eabi-gdb" terminal :

Exception: SWDP invalid ACK

SW-DP scan failed!

I've honestly no idea anymore to debug the situation, so I ask you if you have any idea for me. My circuit is kept very simple, for instance there is only the MCU, the reset button with capacitor, another capacitor for the MCU power, and a 3v3 voltage regulator that is correctly powered from a 12V battery. Voltages are correct, reset pin is normally pulled high and gets to 0V when i press the button (correct behavior). With and without connecting RST wire doesn't change anything. I've tested on 4 different PCBs (of the same design) and the behavior is always the same.

Thanks in advance for your help,

[Tesla DeLorean]

Check part orientation, power to VDDA

Would try with an ST-LINK, and utilities, in Windows.

You could also test for the responsiveness of USART to system loader requests, ie 9600 8E1, sending 0x7F pattern, seeing 0x79 response.

[Loïc]

Hello all,

This works now. It was just about pressing the nRST button while sending commands.