Guidance; Best Practices - Kauai Labs navX2-MXP User Manual

Guidance

Best Practices

This page summarizes the recommended best practices when integrating a navX-sensor with the National
Instruments RoboRIO™. Following these best practices will help ensure high reliability and consistent
operation.
1) Secure the navX-sensor circuit board to the Robot Chassis
Excessive vibration will reduce the quality of navX-sensor measurements. The navX-sensor circuit board
should be mounted in such a way that it as firmly attached to the robot chassis.
2) Plan for RoboRIO Brownouts
The RoboRIO contains circuitry to remove power from the MXP connector when it detects an input
voltage drop below a certain voltage level; this is known as a Stage 2 brownout. While brownouts do not
typically occur during a FRC match (since fresh batteries are typically used at these times), during
practice matches brownouts are common. If the robot drive train draws large amounts of current, even for
a short time, brownouts could potentially occur even with a FRC match.
navX-sensors maintain state information that will be reset when the navX-sensor circuit board is
restarted. Avoiding navX-sensor restarts is very important if your robot software uses the "yaw" angle.
To avoid a navX-sensor restart when stage 2 brownouts occur, a secondary power supply for the navX-
sensor circuit board should be provided. Fortunately, the RoboRIO provides just such a power supply,
since its onboard USB interface is powered by a boost regulator which will provide 5V of power even
when the RoboRIO input voltage (VIN) drops as low as 4.4 volts (once the RoboRIO VIN drops lower
than this, the RoboRIO itself will restart).
To address this situation, simply connect a
RoboRIO; if a brownout does occur, the navX-sensor circuit board will automatically switch to use power
from the RoboRIO's USB port.
3) Understand and Plan for Calibration
Gyro/Accelerometer Calibration
understand this process, and ensure that it completes successfully each time you use the robot.
If your robot moves during calibration, or if noticeable temperature changes occur during calibration, the
calibration process may take longer than normal.
Using the navX-sensor yaw angle before calibration completes may result in errors in robot control. To
avoid this situation, your robot software should verify that calibration has completed (e.g., by calling the
Guidance
Best Practices
USB cable from the navX-sensor circuit board to the
is vital to achieving high-quality navX-sensor readings. Be sure to
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