The Vex Microcontroller

The Vex Microcontroller


The VEX Cortex Microcontroller coordinates the flow of information and power on the robot. This is the robot’s brain, so all other electronic system components must interface to the microcontroller to allow a robot to function properly. Here are its parts and specifications:

STMicroelectronics ARM Cortex-M3 user processor Wireless with built-in VEXnet technology (8) Standard 3-wire Motor ports (2) 2-wire Motor ports (1) I2C "smart sensor" port (2) UART Serial Ports (8) Hi-res (12-bit) Analog Inputs (12) Fast digital I/O ports which can be used as interrupts Programmable with easyC (a drag and drop, VISUAL programming language that requires very little training) for Cortex or ROBOTC for Cortex & PIC

The VEX Microcontroller allows all other system components to function as a cohesive unit. It contains the robot's program and processes all signals received from both human operators and onboard sensor systems. It also manages power allocation on board the robot, and directly controls the motors.

Motor Ports: Connect up to (8) VEX motors or servos. Interrupt Ports: Interrupts are digital inputs designed for high priority signals that need immediate attention from the Microcontroller. Digital/Analog Input Ports: 16 multipurpose input/output ports for sensors. TX/RX Ports: Allow the user to communicate directly with the user processor inside the Microcontroller via a TTL serial port. Serial Port: Use with the VEX Programming Kit to re-program the Microcontroller. Rx1 and Rx2 Ports: Connect radio receivers to communicate with the Microcontroller wirelessly from a Transmitter. Battery Port: Connect a 7.2V power sources, such as the Battery Holder or the VEX 7.2V Robot Battery.

Here are the PIC Microcontroller V0.5’s parts and specifications:

- Wireless with the 75MHz receiver and transmitter Microchip PICmicro® PIC18F8520

- Speed:10 MIPS (Million Instructions Per Second)

- RAM:1800 bytes + 1024 bytes EE2

-Flash:32K program space

- (16) Digital I/O, Analog In Digital In:50 KHz input frequency Analog In:10-bit resolution 10 ìSec access time I/O Schematic: Schematic

- (6) Interrupt I/O

- Usage: Measuring Input changes via software interrupt (1) Serial Port

- Usage: Reprogramming and debugging

- Speed: 115Kb

Programmable with easyC, ROBOTC, or MPLAB 10 MIPS processor speed 32K program space 100,000 erase/write cycles 16 digital input/output ports 8 PWM motor/servo outputs Usage: For VEX motors or servos Type: Hobby standard PWM Refresh: Every 18.5 mSec

Here are the VEX microcontroller’s specifications in terms of performance: Digital input frequency: 50 KHz Analog input access: 10 ìsec User microcontroller: Microchip PICmicro® PIC18F8520 Processor speed: 10 MIPS (Million Instructions Per Second)

Programming: Language: PIC C Program space: 32 K words = approximately 128 KB (hex file) RAM: approximately 2 KB, for memory-mapped I/O and PIC devices EEPROM: approximately 1 KB, for data memory Programming tools: Microchip MPLAB IDE, easyC, or text-editor/Makefile C18 Compiler

The size of an average Vex micro controller is 4.5 in W x 3.9 in L x 1.1 in H with a weight of about .278 lbs (126 grams). It costs anywhere from $150 to $250.

Vex Microcontroller at Vex Robotics