The micro:bit should buffer characters it receives until \n or \r is received (the enter key is pressed on the host computer). The characters should then be printed back in reverse order to the host computer. The characters may also be echoed like earlier to see what is being typed.

1. Letter a is typed and transmitted to the micro:bit
2. (optional) The micro:bit retransmits the letter a (echo)
3. Letter b is typed and transmitted to the micro:bit
4. (optional) The micro:bit retransmits the letter b (echo)
5. Enter key is pressed and \r is transmitted to the micro:bit
6. Letters ba are transmitted from the micro:bit

• Heapless