uC/OS-II friendly UART communication

Using interrupts will work well. Just use your ISR to populate a buffer with the characters as they are received and move a head pointer. Then poll the head and tail pointers of your buffer in your main loop. If the head and tail don't match then write the character to memory(or whatever you need to do with it) and move your tail pointer. Use as many buffers as you have UARTs. You can also populate a buffer and send characters from it by polling in your main loop as well.