The serial port is the main interface to the onboard Linux computer, the wireless network and GPS modules.
Hardware flow control is done using the RTS/CTS pins.
- RTS: Request to send. This pin is issued by the receiver high it he can accept data on its RX line.
- CTS: Clear to send. This allows the sender to sense wether he can send data or not (high: ok, low: buffer full)
RTS/CTS are cross-over like RX/TX are.