I built a custom board that uses a STM32F411CEU6. My problem is that tried to upload a simple blink sketch (I'm using Arduino IDE with STM32 libraries) and I get the error:
ST-LINK SN : 57FF72067166535645342467
ST-LINK FW : V2J37S7
Board : --
Voltage : 3.23V
SWD freq : 4000 KHz
Connect mode: Under Reset
Reset mode : Hardware reset
Device ID : 0x431
Revision ID : Rev A
Device name : STM32F411xC/E
Flash size : 512 KBytes (default)
Device type : MCU
Device CPU : Cortex-M4
Memory Programming ...
Opening and parsing file: Blink.ino.bin
File : Blink.ino.bin
Size : 11256 Bytes
Address : 0x08000000
Erasing memory corresponding to segment 0:
Erasing internal memory sector 0
Error: failed to erase memory
Error: failed to erase memory
RUNNING Program ...
Address: : 0x8000000
Warning: The core is locked up
Start operation achieved successfully
the selected serial port Start operation achieved successfully
does not exist or your board is not connected
I'm using an ST-LINK V2 USB pen that works fine. I have a Black Pill with the same STM32 to use as a control and everything works ok.
Also, when I try to check the custom board with STM32CudeProgrammer, I get the error:
22:16:27 : Size : 1024 Bytes
22:16:27 : Address : 0x8000000
22:16:27 : Read progress:
22:16:27 : Error: Data read failed