Frequently Asked Questions

What is brownout?
As described in RoboRio Brownout and Understanding Current Draw, the RoboRIO will remove power from the MXP connector if the unregulated Input Voltage (VIN) to the RoboRIO drops below 6.3VDC.

Thus, if the navX -MXP is connected to the RoboRIO via the MXP connector and a Stage 2 brownout occurs, the navX-MXP will shutdown until the RoboRIO VIN voltage is again > 6.3VDC.

If the navX-MXP power input is removed during operation this will cause a yaw angle discontinuity – since the currently calculated yaw angle is based upon in-memory calibration coefficients.

Fortunately, the navX-MXP has a USB input, and has on-board circuitry to automatically switch over to the USB input for power and a capacitor to ride-over the switching period. A comprehensive way to allow the navX-MXP to continue to operate even in the face of a RobRio Stage 2 brownout is to modify a power-only USB connector (5VDC and ground leads only), and connect it to one of the VRM’s 5VDC outputs. The VRM buck/boost regulator configuration allows it to provide 5VDC down to a VIN of 3.6V, by which time the RoboRIO would have completely shutdown.

Using this approach, the navX-MXP will continue to be powered even when the RoboRIO VIN drops below the level where the RoboRIO has completely shutdown (Stage 3).

Last Updated 5 years ago

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