STM32F303C6 board has own 3.3 volt LDO with SWD interface. With USB based SHIWAKI Metal ST-Link V2 debugger, the board connection and flash programming works fine. With ST-LINK/V2 [www.st.com/stlinkv2/] board not working now. Earlier it was working. I suspect there is some issue with debugger and not sure why the voltage reports 1.56V or less.
SWD - MCU connection are -
SWCLK - PA14
SWDIO - PA13
GND - GND
RESET - MCU RESET
Find below STCubeProgrammer log with different voltage reporting with only ST-Link V2 debugger connection to computer.
15:15:10 : ST-LINK SN : 48FF74066580515316330367 [ With SHIWAKI Metal ST-Link V2 debugger]
15:15:10 : ST-LINK FW : V2J37S7
15:15:10 : Voltage : 3.19V
15:15:10 : Error: No STM32 target found!
15:17:06 : Warning: Device changed, refreshing...
15:17:06 : ST-LINK SN : 35FF72064D53373251552143 [ With [www.st.com/stlinkv2/] debugger]