If I am reading it correctly in the BBB SRM, UART5_TXD and UART5_RXD are used as two of the pins used to control the boot mode of the processor. I would assume that this means that UART5 should not be used for any device that might be transmitting data during the BBB boot cycle. Can someone verify this ?



correct, if you plan to do this you will need to gate the incoming UART signals to hold off until after boot

That is what it means. It is described in the System Reference Manual. That is a good source to verify things. This applies to ALL of the SYSBOOT pins as well.