Introduction

FIRST leaders have selected the NI CompactRIO embedded control platform as the controller for the 2009 FIRST Robotics Competition. This article provides a high-level overview of how CompactRIO communicates with external devices and how it transfers information to and from the onboard real-time processor.

Figure 1. The Robotics System Architecture with the New NI cRIO-FRC

1. Control

The cRIO-FRC is the core of the robotics control system. It combines several hardware components in a compact form factor to provide processing and connectivity on a stand-alone platform. A customized version of the CompactRIO programmable automation controller, the cRIO-FRC will be offered for the 2009 FIRST Robotics Competition. This device combines a real-time controller and field-programmable gate array (FPGA) in a single unit. CompactRIO hardware components include:

• Embedded real-time processor - an industrial 400 MHz Freescale MPC5200 processor that provides deterministic execution of code on the Wind River VxWorks real-time operating system

• FPGA - a programmable hardware unit that offers control and low-level processing for the I/O interfaces

Figure 2. CompactRIO delivers rugged measurement and processing on a single platform.

Data Transfer To and From the Onboard Real-Time Processor

Fast communication throughout the system is ensured by DMA transfers from the FPGA to the real-time controller that occur over a high-speed PCI bus. The DMA engine transfers data directly from the FPGA to the onboard memory of the real-time controller. This frees up the processor to focus on other tasks like signal processing and analysis, data logging, and communication. Figure 3 illustrates the layout of the CompactRIO architecture.

Figure 3. Overview of Data Transfer within CompactRIO

2. Data Display

A host PC or laptop provides:

• A development environment for LabVIEW or C-based programming, which run on the CompactRIO real-time processor

• Wireless debugging for both C and LabVIEW programs

• The ability to create a customized user interface to display data from a robot

Figure 4. A laptop or host PC provides a user interface for programs running in real time. The user interface in this figure was created with LabVIEW.

3. Driver Control

A driver station, which controls the robot, connects to both the host PC and a wireless access point via Ethernet. The driver station includes:

• An LCD to display robot information

• USB ports that connect to input devices such as joysticks

• Additional I/O that allows students to use

• digital and analog input pins on the driver station to build their own controls

4. Communication

Communication to a driver station or laptop is implemented with 802.11 wireless Ethernet and two wireless access points. Wireless Ethernet provides:

• Communication between the robot and the driver station

• Wireless programming, debugging, and robot control

5. Vision

A camera is for image acquisition. CompactRIO processes the acquired data on the real-time processor and routes images to the host PC for display. The camera connects directly to CompactRIO with an Ethernet cable.

6. I/O

The NI C Series I/O modules listed below interface with external devices such as sensors and actuators. For more information on these modules, see the cRIO-FRC specifications.

• NI 9403 – 32-channel, 5 V/TTL, sinking/sourcing digital I/O module

• NI 9201 – 8-channel, ±10 V, 500 kS/s, 12-bit analog input module

• NI 9472 – 8-channel, 24 V logic, 100 µs, sourcing digital output module

Figure 5. NI offers interchangeable C Series modules to connect to a variety of sensors and actuators.

7. Signal Routing

Digital and analog sidecars connect actuators and sensors to the NI 9403 digital I/O module and the NI 9201 analog input module.

8. Sensors and Actuators

Specific sensors and actuators are yet to be determined. They will be comparable to those available in previous competitions.