Resolved! 1.8V VDD and 3.3V VUSB
Some STM32's have VDD and VDDUSB. Setting VDD to 1.8V and VDDUSB to 3.3V, the GPIOs work at 1.8 V, and USB keeps working (the USB transceiver needs 3.3V). Each time, there is a note that VDDUSB has to be the last power supply to be active when poweri...