Vex CORTEX Quick Start Manual

CORTEX Microcontroller and Joystick Quick Start Guide

This is a Quick Start Guide for using the VEX CORTEX Microcontroller and VEX Joystick. Refer to the VEX Wiki
(http://www.vexforum.com/wiki/index.php/VEX_Cortex_Microcontroller) for updates to this document.

1. Basic connections; batteries, microcontroller, joysticks and (2) VEXnet keys.
a. Attach 7.2v battery power and a VEXnet 802.11g key to the VEX CORTEX as shown.

b. Add AAA batteries to the Joystick by loosening the screw as shown. Remove the battery cover.

c. Install six identical batteries as shown. Use Alkaline, Ni-Cad or Ni-MH chemistries, but DO NOT mix different

chemistry batteries. Charge rechargeable batteries only with a quality charger designed for your battery chemistry.

0510

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CORTEX Microcontroller and Joystick Quick Start Guide

d. 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 add the VEXnet 802.11g key as shown.

e. For longest battery life, turn ON the units only when needed. Fresh batteries in the Joystick will provide about two

hours of run time. If wireless operation is not required, substitute the VEXnet keys with a USB A-A cable. For this

tether conguration, turn ON the CORTEX but leave the Joystick OFF. The USB A-A cable will power the Joystick.

f. Turn ON the CORTEX Microcontroller and the Joystick by setting the power switches to ON as shown in the two

pictures below.

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CORTEX Microcontroller and Joystick Quick Start Guide

g. A valid link is as shown. The VEXnet light will be blinking a fast green on both units. The Robot light will wink green

(be mostly on) on both units and when using fully charged batteries. It will take about 10 to 15 seconds for a link to
be established. The Joystick light will be solid green when using fully charged batteries.

h. If the units fail to link up, turn them both OFF and back ON. If they still fail to link up, tethering may be required.

Refer to the Tethering document for tethering instructions.

2. Basic Conguration

A few examples of the Default Code that is pre-programmed into the Cortex Microcontroller are shown below. For
complete details on the Default Code, refer to Section 3.

a. Add motors and test. The following picture shows 276-2163 VEX Motors plugged into Motor Port 2 and Motor Port

5. With 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.

3 2

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.

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CORTEX Microcontroller and Joystick Quick Start Guide

c. Two Joystick Operation: The default code allows two Joysticks to control motors when a jumper is installed in CORTEX

location Digital 11. Connect the two Joysticks together using the PARTNER Ports with a coiled handset cord as
shown. Only one Joystick should have a VEXnet key installed. The Joystick to Joystick connection is shown below.

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 Joystick Quick Start Guide

3. Default Operation: Refer to the attached gures for details and options of Joystick input to Motor response. These motor

directions will make a Protobot robot go forward when the sticks are pushed “up”. Robots that do not have an idler
gear will go in the opposite direction until a reversing jumper is installed or custom code is created. Note the Jumper
variations for each section.

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CORTEX Microcontroller and Joystick Quick Start Guide

Arcade Mode - Channel 1 (right stick, X-axis) + Channel 2 (right stick, Y-axis)

Motor 3

LEFT DRIVE

Joystick Right = Motor CW

Robot Forward Speed

Reverse Motor Direction

Channel 1 (right stick, X-axis)

Robot Turn Rate

Channel 2 (right stick, Y-axis)

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

Motor 1 LEFT DRIVE Joystick Right = Motor CW
Motor 2 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

Motor 1 LEFT DRIVE Joystick Up = Motor CW
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

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. Shown is the interconnect sketch for wireless reprogramming. For non-wireless

reprogramming, the VEXnet keys may be substituted with a USB A-male to A-male cable.

PC

276-2186

Programming

Cable

USB Port

Program

Port

Joystick

Microcontroller

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CORTEX Microcontroller and Joystick Quick Start Guide

Robot

VEXnet

Game

Blip (yellow)

Startup - looking for USB device

Fast (yellow)

Linking - Searching for VEXnet mate

Fast (green)

Linked

Slow (yellow)

Linked - Data quality reduced

Solid (green)

Tethered

Slow (red)

Fault: Lost Link - Searching for VEXnet mate

Robot [1]

VEXnet

Game

(red)

Main Battery = Dead (<5.5v) or CORTEX Off [2]

(yellow)

Main Battery = Low (<6.5v) [2]

(green)

Main Battery = Good

Solid

All Good: Both Joysticks connected

Solid + 1 Blink

All Good: Tx1 Joystick connected

Fast (red) [3]

Fault: Low Backup Battery (0v-8v)

Note 1: Robot LED only works on Joystick 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.

Robot

VEXnet

Game [4]

Off

No Competition connection

Solid (green)

Driver

Fast (green)

Autonomous

Fast (yellow)

Disabled

Note 4 : Game LED only used when the competition cable is connected.

Game LED only works on the Robot when Linked.

Joystick [5]

(red)

Joystick Battery = Dead (<5.5v)

(yellow)

Joystick Battery = Low (<6.5v)

(green)

Joystick Battery = Good

Fast

Two Joysticks in use

Solid

One Joystick in use

Note 5 : Joystick LED only on Joystick.

4. Diagnostics Information: refer to the following chart for Joystick and CORTEX light patterns and meanings.

Robot, VEXnet, and Game LED’s

show the same data [2]

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CORTEX Microcontroller and Joystick Quick Start Guide

5. Analog Information: Analog lines are input only and read about 62 (0.2 volts) when open. When connected to a 0 to 5v

source, such as the VEX Potentiometer, you will read from near 0 (0 volts) to near 1023 (5 volts).

a. Circuit details:

i. Analog input range is 0 to +5 volts.
ii. Analog circuit has a 470k pull-up to +5 volts, a series 10k resistor and a 20k resistor to ground.
iii. Analog inputs also have a 1000 pF capacitor to ground on the processor side of the 10k resistor.
iv. 3 dB bandwidth: 16 kHz.
v. Circuit connections as shown.

Analog Port

+5 V

470 K

10 K

Analog Input

(Typical)

To Processor

20K

1000 PF

6. Digital Information: When congured as an input, digital lines have a weak pull-up. When congured as an output,

digital lines drive 0 volts for a low and 3.3 volts for a high.

a. Circuit details, Digital Ports 1 through 12:

i. Digital input range is 0 to +5 volts.
ii. 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.
iii. Digital inputs also have a 1000 pF capacitor to ground on the processor side of the 1k resistor.
iv. 3 dB input bandwidth: 16 kHz.
v. Circuit connections as shown.

Digital Port

3.3 V

Weak Pull-up

1 K

Digital Input Output

In Processor

b. Circuit details, SP Digital Port

i. Circuit SP is connected to the Digital-to-Analog-Converter (DAC) output of the User Processor.

ii. Factory default Hex le does not support the DAC output. Check your compiler for availability and use.
iii. SP is an Analog Output when congured 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 Joystick Quick Start Guide

7. 2-Wire Motor Port outputs:
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.

8. 3-Wire Motor Port outputs:
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.

9. UART Connections: Ground, Power (+5v), RX data in, TX data out. Data rate, byte width, (transmit) stop bits, parity,

etc. are determined by the compiler.

a. Default for LCD data: 19,200 baud, 8 data bits, 1 stop bit, no parity and no ow control.

10. I2C Connections: Ground, Power (+5v), Clock, Data. Data rate, byte width, (transmit) stop bits, parity, etc. are

determined by the compiler.

a. The factory default Hex le does not support I2C.

11. Joystick Calibration (optional): Refer to the VEX Wiki (http://www.vexforum.com/wiki/index.php/VEXnet_Joystick).

12. Debugging:
a. Slow blinking green Robot light on CORTEX.

Solution: Try VEXnet Upgrade Utility. If Master Code 4 or earlier, call or e-mail in to VEX Robotics.

b. Slow blinking Robot green light on Joystick.

Solution: Push and hold cong button about 5 seconds until light starts ashing green. Release, wait about 5 seconds,

then turn Joystick OFF and then back ON.
c, Yellow or Red Robot light on the CORTEX. Solution: used fully charged Robot battery.
d. Yellow or Red Robot light on the Joystick, even though the CORTEX is green. Solution: Joystick latches CORTEX’s

lowest battery level. Power cycle both Joystick and CORTEX.

e. Fast red blinking Robot light when plugged in to a competition eld. Solution: Use a fully charged 9v back-up battery

plugged in to the CORTEX.
f. Robot does not shut off when turned OFF. Solution: At the end of the match, remove the Ethernet cable from the

Competition Port of the Joystick. The CORTEX and Joystick will change to non-competition mode. Power off the

Joystick and CORTEX. The CORTEX will shut off in about 5 seconds.
g. Robot does not do what you want it to do. Solution: Download the default code and test to isolate hardware problems.

Then make small program changes testing after each change.
h. Robot still does not link up, even after tethering. Solution: Debug using a friends system to narrow down the problem,

check the VEX Forum or contact VEX Robotics for assistance.

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