I have several servos that can give feedback data that I want to read. The servos use special protocol so I need to use Rx/Tx pin on my Arduino Mega to communicate with them. The problem is that a servo has only one serial communication pin so I cannot use the usual Rx/Tx wiring.
I have heard that there are some hardware configurations to properly convert UART signals to half duplex type. One is to use 2 resistors connected to Rx and Tx of Arduino and the pin of the servo. Another is to use a transistor. However, I could not find exact circuit drawings and rules to choose the values for the resistors or the transistor. Can somebody provide more information on that and explain in terms of hardware exactly how these configurations prevent the Tx writing to the Rx and the servo feedback writing to the Tx.
EDIT: The servo is Dynamixel XL-320 (http://support.robotis.com/en/product/dynamixel/xl-320/xl-320.htm). The communication is half-duplex serial: I can write to the servo, but I can also read values, e.g. load (therefore I need to use both Rx and Tx pins on my arduino). NOTE: the servo manual proposes using a multiplexer and a digital pin on the arduino as a select bit in order to covert uart to half-duplex. However, I am specifically asking for other, more passive alternatives.