HAL UART HAL_UART_Receive Timeout
My apologies.I missed this:
"I’m using a CubeMX generation for STM32F746BETx which contains 2 serial ports. These 2 serial ports are both connected to a putty terminal. (The behaviour is the same for STM32F769I-DISCO and STM32F746G-DISCO.)
I can transmit messages from both and I can also receive messages on one UART. But as soon as I’m receiving characters on both UARTS in the main loop both receive functions return timeout and no character is delivered any more."
Try to change the interrupt of the one port lower than the other. Keep in mind, it is one CPU.