Pololu TReX - Manual (Page 12)

◦ While in Firmware-Upgrade Mode (see Section 6 ):
▪ Red and green LEDs alternate around once per second: The TReX is waiting to see if it should
enter firmware-upgrade mode. This happens when the TReX is in serial mode (i.e. there is no mode
jumper in place), the mix jumper is in place, and the serial out (SO) pin is grounded. This last condition
can arise if the TReX is connected serially to an unpowered microcontroller. Ungrounding the SO pin
will cause the TReX to startup as normal; removing the mix jumper will put the TReX into firmware-
upgrade mode, which will cause the red and green LEDs to start alternating four times faster.
▪ Red and green LEDs alternate around four times per second: The TReX is in firmware-upgrade
mode and is waiting for the short between the serial out (SO) pin and ground to be removed.
▪ Green LED flashes briefly once per second: The TReX is in firmware-upgrade mode and is waiting
for the correct initial serial input sequence. The TReX enters this state when the short between the
serial out (SO) pin and ground is removed after the mix jumper has been removed.
▪ Red LED flashes: There was a faulty input to the bootloader that has caused the bootloader to revert
to waiting for the correct initial serial input sequence. Note: once the firmware upload is complete, the
TReX will reboot and the red LED may flash as part of the startup sequence. This is not an indication
of a firmware-update error. See the firmware-update section for further details.
▪ Green LED rapidly flashes: Everything is proceeding as expected during the firmware upgrade
process. Each successfully uploaded data packet causes the green LED to flash.
3.e. Automatic Calibration for Your RC/Analog Controller
The TReX has the ability to automatically calibrate itself for your particular RC or analog controller. We strongly
recommend you use this feature to calibrate your TReX as it can result in a substantial increase in performance. You
only need to perform the calibration once, but you should recalibrate if you ever change controllers. The TReX can
simultaneously store a set of analog calibration values and a set of RC calibration values; the calibration values used
depends on the mode of operation (or on the value of the “channel input source” parameter if the TReX is running in
serial mode).
The TReX calibrates itself by first learning the neutral values of all the channels and then learning the extremes. You
can enter learning mode via the secret handshake:
1. Power off your TReX.
2. Connect your RC receiver or analog controller to your TReX’s channel inputs.
3. Turn on your RC transmitter/analog controller. Set the sticks to the positions you would like to consider
“neutral” and, if desired, zero your trim settings.
4. Attach the channel-mix jumper.
5. Attach the learning-mode jumper (i.e. short the serial out pin, SO, to ground, G). You must never attach
this jumper while the board is powered!
6. Place the mode jumper to select for either RC or analog (whichever type of controller you’re trying to
calibrate for).
7. Restore power to your TReX. You should see the red and green status LEDs blinking in unison around once
per second.
8. Remove the channel-mix jumper. If you now see the red and green status LEDs blinking together around
four times per second, the TReX is unable to detect a valid RC pulse signal on any of its input channels. If
instead you see the red LED turn on solid, you are now in learning mode, which proceeds in the following four
phases:
Pololu TReX User's Guide © 2001–2013 Pololu Corporation
3. Getting Started Page 12 of 24