Ok so STM32L158VDT6, a ten year old device, where PB0/PC5 are not associated with a U(S)ART on this or any L1 device.
So again perhaps some transposition, or software serial implementation, but a poor choice of pins even for that. Could perhaps use TIM3 to generate patterns.
A quick scan of some clone devices didn't yield any better fit.
If the use is intentional, perhaps a fishing exercise..
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