Resolved! STM32F091, GPIO, USART
If switching GPIOA mode from 'General purpose output' (set to 1) to Alternate function USART Tx:Will level of pin break down for a short time or will it stay rock solid at "1" ?Rem. One has to change MODERy from 01 to 10. One may go via 01 -> 00 -> 1...