Could you try an edit to the STM32F030RC FCD file
32F030RC.fcdx in C:\ProgramData\MatrixTSL\FlowcodeV9\FCD\ARM

Search for name='UART4' and change it to name='USART4'
Similarly name='UART5' and change it to name='USART5'

Then restart Flowcode or re-load the project

Please can you attach your test Flowcode project file and resulting .txt log file

Are SDI and SDO the wrong way round?

Try a C code icon with

Just to add to Martin's comment, a look at the datasheet indicates that A9 could be added to the fcd for SPI2 CLK, but not A12.
edit: The circuit diagram shows port C pin 12, using SDIO interface, which Flowcode doesn't support.
Suggest trying software SPI mode?

Hi Brendan,
I am not getting any hang.
Could you attach a sample program that demonstrates the issue?
For example, are you initializing the UART component?

I think the issue here is that you shouldn't mix interrupt driven comms with a polled timed loop.

I've put the code into the CAL file (STARM_CAL_RTC.c)
this goes into directory...
C:\ProgramData\MatrixTSL\FlowcodeV10\CAL\STARM\
This will avoid the need for the extra C icon code.
Note that if you swap between LSI and LSE you need to cycle all power

I found a little time to play with STM32F DFU programming via the USB bootloader, this avoids needing the ST-link programmer. This has been tested with a WeAct STM32F411CE 8MHz Black Pill dev board. First install the STM32CubeProgrammer from www.st.com (at default location) Here's an FCD with modifi...