Arduino for STM32

google search for RM0008 stm32f103
you should get this
https://www.st.com/resource/en/reference_manual/cd00171190-stm32f101xx-stm32f102xx-stm32f103xx-stm32f105xx-and-stm32f107xx-advanced-arm-based-32-bit-mcus-stmicroelectronics.pdf

look in the chapter for ADC, look under temperature sensor section ...

if you can output to the serial monitor
I'd suggest patch Serial.print() statements in the code, to see what is happening
there are some things that is a little curious
https://github.com/bmellink/IBusBM/blob/master/src/IBusBM.cpp#L84

#if defined(_VARIANT_ARDUINO_STM32_)
void IBusBM::begin ...

check the core you used. it may help to have #include <Arduino.h> in there, normally not needed.

that should work for 'official' core, e.g.
on datasheet, section 5.3.4 Embedded reference voltage
https://www.st.com/resource/en/datashee ... f103c8.pdf
that is the adc value you get for the internal voltage 1.2v

stm32(f103) do not use a 'reference voltage' as like the Atmega.
the top of the range is 3.3v VDD, bottom is 0v GND

if you want to read the internal AVREF in stm32f103 you could try using these
https://github.com/stm32duino/wiki/wiki/API#adc-internal-channels

look up the specs sheet for what that ...

i looked at some codes
https://github.com/fsagbuya/variant-acsip/blob/main/ACSIP_S76S/variant.cpp
it seemed you are using HSI? i.e. internal on chip oscillator

can you try using one of the generic variants?
choose one of those boards e.g. Generic L072RBTx or Generic L072RZTx

I'm guessing they may ...

While you make the variant
there are quite a few dependencies
I'd suggest take a look at how others did it with the custom boards
here is an entry in boards.txt for Piconomix PX-HER0 board
https://github.com/stm32duino/Arduino_Core_STM32/blob/main/boards.txt#L4184
their specific variant files are ...

you could start with a 'generic' variant.

the art of making a variant is, make a copy of the structure all the files in the variant. e.g. use generic as example
then make something similiar and update boards.txt similarly.

then one of the more important things is if you want to use HSE - your ...

I'm not familiar with the requirements of USB host, i think host is 'a lot more difficult' vs being a device. among the things, it needs to enumerate buses/devices, poll the buses/devices, power the buses etc.
nevertheless someone has done something, it isn't yet committed, but you could probably ...

copy out that tools folder, that you found, that stm32flash utility and script can still be used for manual firmware install.

install your core base on this
https://github.com/stm32duino/wiki/wiki/Getting-Started
this is the 'official' stm32duino core.

you would need to select your board (it won't ...