Pololu TReX Jr - Manual (Page 9)

to upgrade its firmware. When placed across the SO and G pins, this jumper puts the TReX Jr into learning/
firmware-upgrade mode via the “secret handshake” (see Section 3.e). The TReX Jr ships with this jumper in
place since we recommend your first step be to calibrate for your controller. This jumper should be removed
before you begin normal operation.
Warning: You should never add this jumper while the board is powered! Disconnect power from the
board, add this jumper, and then reconnect power.
3.d. LED Feedback
This section explains the meanings of the various illumination patterns of the TReX Jr’s LEDs. The TReX Jr has
eight colored LEDs as shown below:
TReX Jr LEDs
• Power LED (1): The blue power LED is located on the right side of the board. When it is brightly
illuminated, the TReX Jr is receiving power and is running. Note that the power LED can occasionally glow
dimly when the TReX Jr is unpowered if it is connected serially to a powered device.
• Motor LEDs (5): Motors 1 and 2 each have two indicator LEDs—one red, one green—tied directly to the
motor outputs. These LEDs are located along the lower edge of the board flanking the motor/power connection
block. For a given motor, the color of the illuminated LED indicates its direction and the intensity indicates its
speed. Our convention is to consider the direction indicated by the green LED “forward” and the direction
indicated by the red LED “reverse”. The auxiliary motor output is directly tied to the yellow LED on the right
side of the board near the auxiliary motor port; the intensity of this LED indicates the auxiliary motor speed.
• Status LEDs (2): The TReX Jr has two status LEDs—one red and one green—located near the middle of
the board. These LEDs are used to communicate a great deal of information to the user. The illumination
patterns mean different things depending on the TReX Jr’s state.
◦ On TReX Jr Startup:
▪ Status LEDs flash rapidly five times: When the TReX Jr starts up, it signals which channels it has
learned by flashing its status LEDs five times. A green flash indicates the corresponding channel has
been learned; a red flash indicates the corresponding channel has not been learned. For example, a
flash sequence of “red, red, green, red, green” means only channels 3 and 5 have been learned. If the
TReX Jr is in analog mode, it signals which analog channels have been learned; if it is in RC mode, it
signals which RC channels have been learned; if it is in serial mode, the learned-channel signals are
Pololu TReX Jr User's Guide © 2001–2009 Pololu Corporation
3. Getting Started Page 9 of 23