Solved
Minor error in CMSIS-mandated device headers (yes, in Cube)
Posted on April 26, 2017 at 12:22
[STM32Cube_FW_F4_V1.15.0]\Drivers\CMSIS\Device\ST\STM32F4xx\Include\stm32f4*.h:
#define USART_CR1_TXEIE USART_CR1_TXEIE_Msk /*!<PE Interrupt Enable */
The comment is misleading (I know, copy/paste error).
JW
