What are the differences between the different serial protocols, RS232, RS423, RS422 and RS485?
RS232 uses single ended TX and RX. This means a common ground wire is shared between TX and RX. Only 3 wires are needed for a data only serial channel: TX, RX, and GND. Disadvantages of single ended signaling is that it is more susceptible to noise than differential signaling, effective cable distances are shorter and data rates are slower. The voltage ranges of RS232 signaling is +3V to +15V for a “high” and -3V to -15V for a “low”. RS423 uses single ended TX and differential RX. TX is comprised of 2 wires: TX+, a single ended signal, and TX- (which is really just GND). RX is comprised of RX+ and RX-, which go into a true differential receiver. So, 4 wires are needed for a data only serial channel: TX+, TX- (GND), RX+ and RX-. The single ended TX+ pin drives the RX pin of an RS232 port, the TX- (GND) just ties to the RS232 GND pin and provides a common GND. The voltage levels of signaling is +5V for a “high” and -5V for a “low”, which is within the RS232 voltage level ranges mentioned
