Pololu Simple - Manual (Page 36)

The TXIN Pin in Detail
The TXIN pin is a special input that allows multiple Simple Motor Controllers to be chained together without
requiring an external AND gate. The following diagram shows how multiple motor controllers can be connected to a
single microcontroller UART:
Wiring diagram for controlling multiple Simple Motor Controllers with single TTL serial source,
such as a microcontroller.
Inside each Simple Motor Controller, an AND gate is used to combine the input from the TXIN pin with the
controller’s serial transmissions. As long as only one chained controller is transmitting at any given time, the above
method of chaining will funnel the transmissions of all chained devices to a single microcontroller receive line. The
following diagram shows the internal circuitry of the TX and TXIN pins:
Schematic diagram of the Simple Motor Controller
TXIN and TX pins.
See Section 6.6 for more information on connecting multiple controllers on the same serial line.
Pololu Simple Motor Controller User's Guide © 2001–2014 Pololu Corporation
4. Connecting Your Motor Controller Page 36 of 101