Cortex Microcontroller and VEXnet Joystick User Guide
1. Cortex Microcontroller and VEXnet Joystick Pairing Procedure:
a. The Joystick must rst be paired to the Cortex Microcontroller before they will work using the VEXnet Keys. Pairing
requires a USB A-A Cable and a VEX 7.2V Battery. This process must be completed each time you use a Joystick
or Cortex with a new mate. A Joystick can only communicate with a Cortex that it has been paired with. During the
Pairing Process, the ID from the Cortex is transferred to the Joystick; thus mating the two units together.
b. Start with the Cortex and Joystick turned OFF.
c. Connect the Cortex to the Joystick using a USB A-A Cable.
d. Connect the 7.2V Robot Battery to the Cortex.
e. Power up only the Cortex.
f. A successful tether is indicated by a Solid Green VEXnet LED on both the Joystick and the Cortex (See Figure Below).
– The Solid Green VEXnet LED must remain ON both units at the same time for a minimum of 5 seconds.
– Disregard the other LEDs as you are only interested in the VEXnet LED.
– Pairing may take up to one minute to complete.
g. Once the units have nished pairing, turn OFF the Cortex.
h. Disconnect the USB A-A Cable from both units.
i. Disconnect the 7.2V Robot Battery from the Cortex.
0114
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Cortex Microcontroller and VEXnet Joystick User Guide
2. Basic connections; batteries, microcontroller, Joysticks and (2) VEXnet keys.
a. Attach a 7.2v battery and a VEXnet USB Key to the Cortex as shown.
b. Install six identical batteries as shown. Use Alkaline, Ni-Cad or Ni-MH type batteries, but DO NOT mix different
kinds of batteries. Charge rechargeable batteries only with a quality charger designed for your battery type.
c. Reinstall the battery cover (insert the two tabs of the battery cover rst along the back edge of the battery cover to aid
in installation) and then tighten the cover screw. Then add the VEXnet USB Key as shown.
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Cortex Microcontroller and VEXnet Joystick User Guide
d. You can also power your Joystick directly from a standard wall outlet using the Joystick Power Adapter (276-1710).
Simply plug this cable into your Joystick’s PROGRAM/FACTORY port and you can operate your Joystick without the
use of batteries. Please note: when using the Joystick Power Adapter, it is not necessary to turn your Joystick ON.
Also, the JOYSTICK/POWER LED can be ignored.
e. Turn on the Cortex and Joystick by setting the power switches to ON as shown in the two pictures below.
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Cortex Microcontroller and VEXnet Joystick User Guide
f. A valid link is shown below. The VEXnet LED will be blinking fast green on both the Cortex and Joystick. The VEXnet
light is the only LED that determines a valid link. It usually takes 5 to 10 seconds to successfully establish a link. Once
the units are linked, the Robot and Joystick LED Indicators will show the battery levels in their respective unit. A
green Robot or Joystick LED indicates that their respective batteries are fully charged batteries. As the battery levels
decrease, these LEDs will change to yellow and then red.
g. If the units fail to establish the VEXnet link after 30 seconds, turn them both OFF and then back ON. If they still fail
to link up, refer to the Troubleshooting Flowchart in section 7.
3. BasicConguration
A few examples of the Default Code that is preloaded onto the Cortex Microcontroller are shown below. For complete
details on the Default Code, refer to Section 4. Please note: The default code for the Cortex Microcontroller varies
from that of the PIC Microcontroller. Please review and follow the tables in this document to ensure your robot
behaves in the manner you wish.
a. Add motors and test. The following picture shows two VEX 3-Wire Motors plugged into Motor Port 2 and Motor
Port 5. With the Default Code, pushing Joystick Channel 3 up will cause Motor 2 to turn clockwise. Pushing Joystick
Channel 2 up will cause Motor 5 to turn counterclockwise.
b. Motor Reversing: The Default Code allows jumpers or switches to be installed in the Digital Ports to invert the motor
direction. This is useful to correct the direction of motors without changing code, or when using a switch to reverse a
motor if the robot hits an object. The following picture shows motor reversing jumpers installed in Digital Ports 2 and
5 to reverse Motor Ports 2 and 5. If you are using 2-wire motors, another way to invert the motor’s direction is to
reverse the motor’s connection where it is plugged into a Motor Controller 29 Module or Motor Ports 1 or 10 on the
Cortex.
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Cortex Microcontroller and VEXnet Joystick User Guide
c. Two Joystick Operation: If desired, a second Joystick can be added to allow two drivers to operate a single robot.
Simply connect a second VEXnet Joystick or a Partner Joystick to your main VEXnet Joystick using a coiled handset
cable plugged into the Joysticks’ PARTNER Ports. Only the main Joystick should have a VEXnet Key installed.
When using the Default Code, you will need to install a jumper into Digital Port 11 in order to activate two-Joystick
operation.
d. Limit Switch Inputs: The Default Code allows jumpers or switches to be installed in the Analog Ports to limit certain
motor directions. These are useful for stopping a motor when an arm bottoms out. A limit switch plugged in to
Analog 1 will stop Motor 6 from turning counterclockwise when activated. A limit switch plugged in to Analog 2 will
stop Motor 6 from turning clockwise when activated.
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Cortex Microcontroller and VEXnet Joystick User Guide
4. DefaultOperation:RefertotheattachedguresfordetailsandoptionsofJoystickinputtoMotorresponse.
These motor directions will make a Protobot robot go forward when the joysticks are pushed up. Note the Jumper
variations for each section.
Please note: The default code for the Cortex microcontroller varies from that of the PIC microcontroller. Please
review and follow the tables in this document to ensure your robot behaves in the manner you wish.
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Cortex Microcontroller and VEXnet Joystick User Guide
Arcade Mode - Channel 1 (right stick, X-axis) + Channel 2 (right stick, Y-axis)
Channel 1 (right stick, X-axis)
Motor 1
LEFT DRIVE
Joystick Right = Motor CW
Robot Turn Rate
Motor 2
LEFT DRIVE
Joystick Right = Motor CW
Motor 3
LEFT DRIVE
Joystick Right = Motor CW
Motor 4
RIGHT DRIVE
Joystick Right = Motor CW
Motor 5
RIGHT DRIVE
Joystick Right = Motor CW
Motor 10
RIGHT DRIVE
Joystick Right = Motor CW
Channel 2 (right stick, Y-axis)
Motor 1
LEFT DRIVE
Joystick Up = Motor CW
Robot Forward Speed
Motor 2
LEFT DRIVE
Joystick Up = Motor CW
Motor 3
LEFT DRIVE
Joystick Up = Motor CW
Motor 4
RIGHT DRIVE
Joystick Up = Motor CCW
Motor 5
RIGHT DRIVE
Joystick Up = Motor CCW
Motor 10
RIGHT DRIVE
Joystick Up = Motor CCW
Reverse Motor Direction
Reverse Motor 1
Jumper in Digital 1
Reverse Motor 2
Jumper in Digital 2
Reverse Motor 3
Jumper in Digital 3
Reverse Motor 4
Jumper in Digital 4
Reverse Motor 5
Jumper in Digital 5
Reverse Motor 6
Jumper in Digital 6
Reverse Motor 7
Jumper in Digital 7
Reverse Motor 8
Jumper in Digital 8
Reverse Motor 9
Jumper in Digital 9
Reverse Motor 10
Jumper in Digital 10
Limit Switch Inputs
Motor 6 ignores CCW
Jumper in Analog 1
Motor 6 ignores CW
Jumper in Analog 2
Motor 7 ignores CCW
Jumper in Analog 3
Motor 7 ignores CW
Jumper in Analog 4
Motor 8 ignores CCW
Jumper in Analog 5
Motor 8 ignores CW
Jumper in Analog 6
Motor 9 ignores CCW
Jumper in Analog 7
Motor 9 ignores CW
Jumper in Analog 8
a. The Cortex may be reprogrammed with user-created code. The hardware setup for wireless downloading is shown
below. For non-wireless downloading, the VEXnet keys may be substituted with a USB A-A cable. You can also
download code directly to the Cortex using the USB A-A cable.
USB Port USB Port
PC PC
VEXnet
Joystick
276-2186
Programming Cable
Program
Port
Cortex
Microcontroller
Cortex
Microcontroller
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Cortex Microcontroller and VEXnet Joystick User Guide
Robot [1]
VEXnet Game
Main Battery = Dead (<5.5v) or CORTEX Off [2]
Main Battery = Low (<6.5v) [2]
Main Battery = Good
All Good: Tx1 Joystick connected
Joystick [5]
Robot VEXnet Game
Joystick Battery = Dead (<5.5v)
Joystick Battery = Low (<6.5v)
Joystick Battery = Good
Joystick [5]
Robot VEXnet Game
Joystick [5]
Robot VEXnet Game
Slow (red) double blink Invaild ID in the Joystick
5. Diagnostics Information: refer to the following chart for Joystick and Cortex LED patterns and meanings.
Joystick [5] Robot VEXnet Game
Note 1: Does not apply to ROBOTC User Code Downloads
Joystick [5]
(red)
(yellow)
(green)
Solid All Good: Both Joysticks connected
Solid + 1 Blink
Fast Autonomous only mode
Fast (red) [3] Fault: Low Backup Battery (0v-8v)
Slow (red) Fault: User Microprocessor Issue
Note 1: Robot LED only work when Linked
Note 2: Lowest CORTEX battery color latched at Joystick and CORTEX
Note 3: No Backup Battery only indicated if competition cable is connected.
Joystick [5] Robot VEXnet Game
Note 4 : Game LED Driver Indicator is only used when the competition cable is connected.
Medium (yellow) Initialize - Looking for PC or Tether Mate
Blip (yellow) Startup - Looking for USB Key
Fast (yellow) Linking - Searching for VEXnet Mate
Fast (green) Linked
Slow (green / yellow) Linked - Data quality reduced
Slow (green / red) Linked - Poor Data quality reduced
Solid (green) Tethered to Mate or PC
Slow (red) single blink Fault: Lost Link - Searching for VEXnet Mate
Slow (green) Downloading User Code [1]
Off No Competition connection
Solid (green) Driver [4]
Fast (green) Autonomous
Fast (yellow) Disabled
(red)
(yellow)
(green)
Fast Two Joysticks in use
Solid One Joystick in use
Note 5 : Joystick LED only on Joystick.
Update Utility Tool Indicators
Slow (green) Flickering (green) Bootload Mode - Ready to update firmware
Slow (green) Slow (red) Flickering (green) Downloading Master Code
Other Indicators
(red) (red) (red) (red) Flash on all 3 indicates a Reset
Slow (red) double blink Invaild ID in the CORTEX
Robot, VEXnet, and Game LED’s
show the same data [2]
Solid (green) Tether to PC
Slow (red) double blink NO VEXnet Key detected
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Cortex Microcontroller and VEXnet Joystick User Guide
6. VEXnet Joystick Calibration Procedure:
a. The Joystick must be linked to the Cortex Microcontroller using the VEXnet Keys.
b. Hold the “6U” Back Switch depressed.
c. While the “6U” Back Switch is depressed, use a small Allen Wrench (1/16” or smaller) or similar small straight tool
to depress and hold the CONFIG Switch.
d. Hold both Switches depressed until you see the Joystick LED Flash red and green – you can now release both
Switches.
– There is a 10 second time limit to complete the following steps 5 and 6.
e. Move both Analog Joysticks to the maximum position desired in all 4 directions – Up, Back, Left, and Right.
–. If a movement is not detected in all 4 directions, a timeout will occur after about 10 seconds and the
Calibration Mode will be discontinued and the VEXnet LED will briey ash red.
–. The Joystick LED will continue to ash red and green during the calibration process.
f. After movement is detected in all 4 directions, the Joystick LED will be ON and solid green.
– To save the calibration, depress and release the “8U” top button.
– If the calibration is accepted and saved, the Joystick LED will start ashing fast green for a few seconds.
– If the calibration is not saved, a timeout will occur after about 10 seconds and the Calibration Mode will be
discontinued and the VEXnet LED will briey ash red.
– To cancel the calibration, depress and release the “7U” top button. The Calibration Mode will be discontinued
and the VEXnet LED will briey ash red.
– If the Calibration Mode is discontinued or saved, the Joystick LEDs will resume their normal function after the
VEXnet LED briey ashes.
g. If Joystick Master Firmware is downloaded into the Joystick, the Joystick will need to be recalibrated.
6U
Cong Switch
7U8U
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Cortex Microcontroller and VEXnet Joystick User Guide
7. General Robot Troubleshooting Flowchart
Start
Does
the Cortex
turn on?
YES
Is the
Robot LED on
the Cortex
consistently
red?
NO
Do all
LEDs
flash Red in a
repeating
cycle?
NO
NO
Is the
YES
Robot LED
blinking?
NO
Robot battery is dead.
Charge or replace batteries
before continuing.
YES
YES
Check batteries and power connections. The battery connectors on
the Cortex can become bent open over time. If necessary, bend the
connectors back in to ensure a solid power connection.
Fast
or slow
blink?
Low or missing 9v backup battery.
If in a competition setting, install a
fully charged 9v backup battery before
Fast
continuing
Slow
Programming error. Try switching to
the Default Code which can be found
within your programming software. If
Single
or double
blink?
Single
this xes the issue, return to your user
code and attempt to isolate the issue to
a particular line of code. The best way
to do this is to comment out various
Double
sections at a time and test after each
change.
Is
Cortex
VEXnet LED
on?
YES
Do all
motors work
correctly?
YES
NO
NO
NO
Is the
VEXnet LED
green?
YES
Are you
having trouble
running your
competition
autonomous
code?
Is the
Game LED
flashing?
NO
YES
Wait 20 second…
YES
Update the VEXnet Firmware (Master CPU Firmware
for ROBOTC users) on both the Cortex and the Joystick
using the Firmware Upgrade Utility included with your
programming software. If you do not have programming
software this utility is available on the Downloads page
at vexrobotics.com.
NO
The Cortex is currently running an Autonomous Only
user code. If you want to use the VEXnet Joystick,
download a VEXnet Enabled project such as the Default
Code using the USB A-A Cable.
If the units are still not correctly linked, refer to the
VEXnet Troubleshooting Flowchart in Section 8.
When programming a competition robot, it’s very
important that you write your code in a competition
template so that the Field Controller will be able to
correctly enable/disable your robot. Note: during
autonomous the VEXnet Joystick is disabled.
Refer to the Motor Troubleshooting Flowchart in Section 9.
For any other issues, you can refer to the other guides or post a question on the
VEX Forum (vexforum.com). You can also contact VEX Technical Support by
phone at +1-903-453-0802 or email support@vexrobotics.com. Please note:
for programming questions contact the developer of your programming software.
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Cortex Microcontroller and VEXnet Joystick User Guide
8. VEXnet Troubleshooting Flowchart
Start
Do
both units turn
on?
YES
Is the
Joystick LED
red?
NO
Are both
VEXnet LEDs
on?
YES
Check batteries
NO
YES
and power
connections.
Update the VEXnet Firmware (Master CPU Firmware for ROBOTC users)
on both the Cortex and the Joystick using the Firmware Upgrade Utility
NO
included with your programming software. This utility is also available on the
Downloads Page at vexrobotics.com.
Single
Double Red
or double
blink?
Single
Is the
Joystick LED
solid?
NO
What color
is the VEXnet
LED?
Other
YES
Flashing
Yellow
Joystick batteries are
dead. Replace batteries
before continuing.
For
longer than 20
seconds?
NO
YES
Pair Cortex and Joystick.
For instructions, refer to
Section 1 of the Cortex
User Guide.
Units are establishing
VEXnet link. No action
required.
Is
VEXnet
LED flashing multiple
colors?
YES
NO
Poor signal strength.Lost VEXnet link.
No VEXnet key detected.
Check key connection
and replace key if
necessary. Powercycle
unit when nished.
Signal may be blocked or units
may be out of range. Consider
moving key to a better location or
consider moving the Cortex closer
to the Joystick.
If the issue is still present after following this guide, update both the Cortex and
Joystick with the most recent version of the VEXnet Firmware (Master CPU
Firmware for ROBOTC users). If this does not resolve the problem, try using
a different set of VEXnet keys. If you need further assistance you can post a
question on the VEX Forum (vexforum.com) or contact VEX Technical Support
by phone at +1-903-453-0802 or email support@vexrobotics.com.
Units are correctly
linked. If the problem
persists, check user code
or try using the Default
Code which is available
from within your
programming software.
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Cortex Microcontroller and VEXnet Joystick User Guide
9. Motor Troubleshooting Flowchart
Start
Do the
Motors spin
at all?
YES
NO
Motor Controller
29 Modules on all
plugged into ports
Are
you using
2-wire motors
2-9 on the
Cortex?
YES
In order to run a 2-Wire Motor off a 3-Wire PWM
motor port you must use a Motor Controller 29 Module
(276-2193) for each 2-wire motor. This motor controller
acts as a converter between a 2-wire motor and a 3-wire
NO
motor port. Ports 1 and 10 on the Cortex are equipped
with built-in Motor Controllers, allowing you to directly
control a 2-Wire Motor on these ports.
Do motors
intermittently lose
power or stop
working?
NO
Are your
motors
drifting?
YES
NO
YES
This could be a programming issue. Try switching
to the Default Code to isolate the problem.
The Cortex is equipped with two 4 amp circuit breakers
that may trip if the motors pull too much current. Motor
ports 1- 5 on the Cortex share one 4 amp circuit breaker.
Ports 6-10 share a second 4 amp circuit breaker. It’s
recommended that you balance the load from your
motors across these two breakers to prevent the circuit
breaker from tripping unnecessarily.
If a motor still looses necessary power it is likely that the motor’s
internal thermal breaker is tripping. This is almost always
attributed to the motor being stalled or placed under too high
of a load. First check your drivetrain or mechanism for any
unnecessary friction. The best way to do this is to disconnect the
motor from your mechanism and then turn the shaft by hand.
Ideally, your mechanism or drivetrain should spin relatively freely.
You may also need to add additional motors to your application or
switch to a slower and less aggressive gear ratio. If you have a highload application and are using 2-wire Motor 269 modules, it may
be a good idea to change them out for 2-wire Motor 393 Modules,
which, in their factory setting, can output 60% more torque.
If any motors are still not
responding, try switching out
motors, motor controllers and
motor ports in order isolate the
issue to a particular piece of
hardware. For additional help,
you can post a question on the
VEX Forum (vexforum.com) or
contact VEX Technical Support
by phone at +1-903-453-0802 or
email support@vexrobotics.com.
Are you
having Issues
with using your
Power
Expander?
NO
The Joystick may need
to be recalibrated. For
instructions, see section
6 of this guide or refer
to the help les included
with you programming
software.
Page 12 of 14
Refer to the Power Expander Inventor’s Guide which
YES
is available at the Product Page at vexrobotics.com.
If you’re still having problems with motors you can refer to the other
guides or contact VEX Technical Support by phone at +1-903-453-0802
or email support@vexrobotics.com. You may also want to post a question
on the VEX Forum and someone in the VEX community will assist you.
Cortex Microcontroller and VEXnet Joystick User Guide
10. Analog Information: Analog lines are input only and read about 0.2 volts when open. Circuit details are as
follows:
a. Analog input range is 0 to +5 volts.
b. Analog to digital resolution is 12-bit, compiler resolution may vary.
c. Analog circuit has a 470k pull-up to +5 volts, a series 10k resistor and a 20k resistor to ground.
d. Analog inputs also have a 1000 pF capacitor to ground on the processor side of the 10k resistor.
e. 3 dB bandwidth: 16 kHz.
f. Circuit connections as shown.
Analog Port
+5 V
470 K
10 K
Analog Input
(Typical)
To Processor
20K
1000 PF
11.DigitalInformation:Whenconguredasaninput,digitallineshaveaweakpull-up. When congured as an output,
digital lines drive 0 volts for a low and 3.3 volts for a high. Circuit details are as follows:
a. Digital input range is 0 to +5 volts.
b. Digital drive is primarily limited by the 1k series resistor, so it can output a 2v high into 2k-ohms to ground or a 0.8v
low into 7k-ohms to 3.3v.
c. Digital inputs also have a 1000 pF capacitor to ground on the processor side of the 1k resistor.
d. 3 dB input bandwidth: 150 kHz.
e. Circuit connections as shown.
Digital Port
3.3 V
Weak Pull-up
1 K
Digital Input Output
In Processor
12.CircuitdetailsoftheDigital-to-AnalogPort,SP:
a. Circuit SP is connected to the Digital-to-Analog-Converter (DAC) output of the User Processor.
b. Factory default Hex le does not support the DAC output. Check your compiler for availability and use.
c. SP is an Analog Output when congured by compiler. Drive is primarily limited by a 5 kilo-ohm internal processor
resistance and by the 100 ohm series resistor. Output swing of the processor into an open load is 0.2v to 3.1v, typical.
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1000 PF
Cortex Microcontroller and VEXnet Joystick User Guide
13.2-WireMotorPortoutputs:
a. Motor Port 1 and Motor Port 10.
b. Maximum motor stall current: 3.0 amps at 8.5 volts.
c. Motor chop rate: determined by the compiler. Default code chop rate: 1 kHz.
d. Overcurrent protection: Motor Port 1 through Motor Port 5 shares one 4 amp circuit breaker. Motor Port 6 through
Motor Port 10 shares a second 4 amp circuit breaker.
14.3-WireMotorPortoutputs:
a. Motor Ports 2 through 9.
b. Maximum motor stall current: internally limited by motor assembly.
c. Motor PWM output: determined by the compiler. Default is 1 to 2 milliseconds high time and a 17 millisecond period.
d. Overcurrent protection: Motor Port 1 through Motor Port 5 shares one 4 amp circuit breaker. Motor Port 6 through
Motor Port 10 shares a second 4 amp circuit breaker.
15. UART Connections:
a. Ground, Power (+5v), RX data in, TX data out. Data rate, byte width, (transmit) stop bits, parity, etc. are determined
by the compiler.
b. Default for LCD data: 19,200 baud, 8 data bits, 1 stop bit, no parity and no ow control.
16. I2C Connections:
a. Ground, Power (+5v), Clock, Data. Data rate, byte width, (transmit) stop bits, parity, etc. are determined by the
compiler.
b. The factory default Hex le does not support I2C.
17. Notes:
a. Do not use a USB Hub with the Cortex or Joystick. Always make a connection directly to a PC USB port when needed.
USB Hub performance is not supported.
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