Pololu TReX - Manual (Page 8)

or SI line should connect to your target’s transmit line (the orange wire in the figure above). On a DB9 connector, pin
2 is your computer’s receive line and pin 3 is your computer’s transmit line.
Warning: It is very important that you do not connect your TReX’s TTL pins (SO and SI) to an
RS-232 port. RS-232 serial communication signals range from -12 to +12 V, which is well outside the
0 – 5 V expected on those lines. Only the COM pins (TX and RX) are designed to handle RS-232
voltages.
3.c. Jumper Settings
The TReX comes with four blue shorting blocks as shown in the picture below. These jumpers let you affect some
aspects of its behavior without serial configuration commands. Note that we recommend you always power off your
TReX before changing jumpers (other than the mix jumper, which can be changed at any time). This is not strictly
necessary, but it is the safest practice.
TReX jumpers
• Channel-Mix (a.k.a. Single-Stick) Jumper: When this jumper is in place, the TReX operates in single-stick
mode. Channel 1 is treated as turn left/right while channel 2 is treated as forward/reverse. When this jumper is
off, channel 1 directly controls motor 1 and channel 2 directly controls motor 2. This jumper may be added or
removed on the fly.
• Battery Elimination Circuit (BEC, a.k.a. +=Vcc) Jumper: When this jumper is in place, the middle column
of channel input pins is connected to Vcc (5 V). You can use this jumper to power your RC receiver or analog
controller through your TReX. If your RC receiver is powered via another source, you must leave this jumper
off.
Pololu TReX User's Guide © 2001–2013 Pololu Corporation
3. Getting Started Page 8 of 24